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The impact of learning to read on visual processing

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Abstract

Reading is at the interface between the vision and spoken language domains. An emergent bulk of research indicates that learning to read strongly impacts on non-linguistic visual object processing, both at the behavioral level (e.g., on mirror image processing – enantiomorphy) and at the brain level (e.g., inducing top-down effects as well as neural competition effects). Yet, many questions regarding the exact nature, locus, and consequences of these effects remain hitherto unanswered. The current Special Topic aims at contributing to the understanding of how such a cultural activity as reading might modulate visual processing by providing a landmark forum in which researchers define the state of the art and future directions on this issue. We thus welcome reviews of current work, original research, and opinion articles that focus on the impact of literacy on the cognitive and/or brain visual processes. In addition to studies directly focusing on this topic, we will consider as highly relevant evidence on reading and visual processes in typical and atypical development, including in adult people differing in schooling and literacy, as well as in neuropsychological cases (e.g., developmental dyslexia). We also encourage researchers on nonhuman primate visual processing to consider the potential contribution of their studies to this Special Topic.
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THE IMPACT OF
LEARNING TO READ
ON VISUAL PROCESSING
EDITED BY : Tânia Fernandes and Régine Kolinsky
PUBLISHED IN : Frontiers in Psychology
1January 2016 | The Impact of Learning to Read on Visual Processing Frontiers in Psychology
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ISSN 1664-8714
ISBN 978-2-88919-716-3
DOI 10.3389/978-2-88919-716-3
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2January 2016 | The Impact of Learning to Read on Visual Processing Frontiers in Psychology
Reading is at the interface between the vision and spoken language domains. An emergent
bulk of research indicates that learning to read strongly impacts on non-linguistic visual object
processing, both at the behavioral level (e.g., on mirror image processing – enantiomorphy -)
and at the brain level (e.g., inducing top-down effects as well as neural competition effects).
Yet, many questions regarding the exact nature, locus, and consequences of these effects remain
hitherto unanswered.
The current Special Topic aims at contributing to the understanding of how such a cultural
activity as reading might modulate visual processing by providing a landmark forum in which
researchers define the state of the art and future directions on this issue.
We thus welcome reviews of current work, original research, and opinion articles that focus
on the impact of literacy on the cognitive and/or brain visual processes. In addition to studies
directly focusing on this topic, we will consider as highly relevant evidence on reading and visual
processes in typical and atypical development, including in adult people differing in schooling and
literacy, as well as in neuropsychological cases (e.g., developmental dyslexia). We also encourage
researchers on nonhuman primate visual processing to consider the potential contribution of
their studies to this Special Topic.
Citation: Fernandes, T., Kolinsky, R., eds. (2016). The Impact of Learning to Read on Visual
Processing. Lausanne: Frontiers Media. doi: 10.3389/978-2-88919-716-3
THE IMPACT OF LEARNING TO
READ ON VISUAL PROCESSING
Topic Editors:
Tânia Fernandes, Universidade de Lisboa, Portugal
Régine Kolinsky, Fonds de la Recherche Scientifique-FNRS, Belgium
3January 2016 | The Impact of Learning to Read on Visual Processing Frontiers in Psychology
Table of Contents
04 Editorial: The impact of learning to read on visual processing
Tânia Fernandes and Régine Kolinsky
06 What is the role of visual skills in learning to read?
Yanling Zhou, Catherine McBride-Chang and Natalie Wong
09 The visual magnocellular deficit in Chinese-speaking children with
developmental dyslexia
Yi Qian and Hong-Yan Bi
16 Reading as functional coordination: not recycling but a novel synthesis
Thomas Lachmann and Cees van Leeuwen
24 Letters in the forest: global precedence effect disappears for letters but not for
non-letters under reading-like conditions
Thomas Lachmann, Andreas Schmitt, Wouter Braet and Cees van Leeuwen
34 Developmental changes in reading do not alter the development of visual
processing skills: an application of explanatory item response models in
grades K-2
Kristi L. Santi, Paulina A. Kulesz, Shiva Khalaf and David J. Francis
47 A cultural side effect: learning to read interferes with identity processing of
familiar objects
Régine Kolinsky and Tânia Fernandes
58 Mirror-image discrimination in the literate brain: a causal role for the left
occpitotemporal cortex
Kimihiro Nakamura, Michiru Makuuchi and Yasoichi Nakajima
65 How does literacy break mirror invariance in the visual system?
Felipe Pegado, Kimihiro Nakamura and Thomas Hannagan
70 Let’s face it: reading acquisition, face and word processing
Paulo Ventura
EDITORIAL
published: 14 July 2015
doi: 10.3389/fpsyg.2015.00985
Frontiers in Psychology | www.frontiersin.org July 2015 | Volume 6 | Article 985
Edited by:
Jessica S. Horst,
University of Sussex, UK
Reviewed by:
Carmel Houston-Price,
University of Reading Malaysia,
Malaysia
*Correspondence:
Tânia Fernandes,
taniapgfernandes@gmail.com;
tpfernandes@psicologia.ulisboa.pt
Specialty section:
This article was submitted to
Developmental Psychology,
a section of the journal
Frontiers in Psychology
Received: 08 June 2015
Accepted: 29 June 2015
Published: 14 July 2015
Citation:
Fernandes T and Kolinsky R (2015)
Editorial: The impact of learning to
read on visual processing.
Front. Psychol. 6:985.
doi: 10.3389/fpsyg.2015.00985
Editorial: The impact of learning to
read on visual processing
Tânia Fernandes 1*and Régine Kolinsky 2, 3
1Faculdade de Psicologia, Universidade de Lisboa, Lisboa, Portugal, 2Fonds de la Recherche Scientifique - FNRS, Brussels,
Belgium, 3Unité de Recherche en Neurosciences Cognitives, Center for Research in Cognition and Neurosciences,
Université Libre de Bruxelles, Brussels, Belgium
Keywords: the impact of learning to read on visual processing, literacy acquisition, reading development,
developmental dyslexia, visual processing, visual object recognition
In 1892, Déjerine published the first report of pure alexia (Déjerine, 1892). Monsieur C. became
unable to read in the absence of any other cognitive disorder (even writing was preserved) after
a lesion of the inferior occipitotemporal cortex, a neural region dedicated to visual recognition.
Although reading is an intense visual ability, the relation between reading and visual processing
has often been sell short. It was only ∼100 years after the report of Monsieur C. that part of this
occipitotemporal region was coined visual word-form area, VWFA (Warrington and Shallice, 1980;
see also Cohen et al., 2000; Polk and Farah, 2002). Since then an emergent bulk of research has
demonstrated that learning to read, not only leads to the emergence of a specialized neurocognitive
circuitry, but also impacts on the evolutionary older and pre-existing neurocognitive system of
visual (non-linguistic) object recognition. Many questions regarding the exact nature, locus, and
consequences of this impact are in debate or still unanswered. This Research Topic was aimed at
setting a landmark forum on which researchers present and discuss recent work, their proposals,
and open novel questions. We have compiled nine excellent articles on the relation between
visual processing and literacy acquisition, reading development, and developmental dyslexia. This
research topic is organized into three parts.
In the first part, opening this research topic, in an opinion article, Zhou et al. (2014) consider the
relation between visual skills and learning to read, and the moderator role of the visual complexity
of the written script in this equation (e.g., Chinese makes stronger demands of visual skills due to its
complexity than alphabetic scripts). Qian and Bi (2014) argue that the visual complexity of the script
modulates the expression of visual processing deficits (namely, in magnocellular processing) in
developmental dyslexia. They examined the association between motion processing (in a coherent
motion task, underpinned by V5/MT functioning) and reading (in a visual lexical decision task) in
Chinese dyslexic children and chronological-age controls.
Second, regarding the emergence of a neurocognitive system specialized in letter processing,
in a hypothesis and theory article, Lachmann and van Leeuwen (2014) propose the functional
coordination approach. According to this hypothesis learning to read captures the analytic strategy
of visual processing, which was already available before literacy took place, but then becomes the
preference mode in letter processing. In their research article, Lachmann et al. (2014) used the
Navon test to examine whether, when the hierarchical stimulus (a global figure composed of local
figures) is presented at fixation with dimensions close to those in written text, letters compared to
non-letters are processed using an analytic strategy instead of the usual holistic strategy adopted on
hierarchical stimuli.
In the last part of this Research Topic, the impact of literacy on non-linguistic visual processing
is considered. Indeed, according to the neuronal recycling hypothesis (Dehaene, 2009) the ventral
occipitotemporal regions, originally devoted to object recognition, are partially recycled to
accommodate literacy, with spillover effects on the former function. In a large-scale developmental
study, Santi et al. (2015) show that the impact of learning to read on visual skills is not observed
at a macro behavioral level assessed with general educational/neuropsychological tests. Note,
4
|
Fernandes and Kolinsky Literacy acquisition & visual processing
however, that studies that reported an impact of literacy on
general spatial skills have examined children learning to read
scripts differing on visual complexity (e.g., Zhou et al., 2014, in
this research topic), but this was not the case in Santi et al.: all
children were learning the alphabetic English orthography. This
might seem, however, inconsistent with the neuronal recycling
hypothesis (Dehaene, 2009). Indeed, a key question, discussed in
the last four articles of this collection, is to understand which
aspects of visual processing are actually affected by literacy
acquisition and why. Possibly only the visual properties that
collide with learning to read are affected. This is the case
of mirror invariance: lateral mirror images, such as d and b,
are originally processed as equivalent percepts. Kolinsky and
Fernandes (2014; following the prior work of Pegado et al.,
2014) examined whether learning to read is able to modify
the object recognition system as expressed by a loss of mirror
invariance, by comparing the orientation cost for mirror images
(e.g., ⌉-⌈) vs. plane-rotations (to which the visual system is
originally sensitive to; e.g., ⌉-⌊), in identity-based same-different
judgments of illiterate, late literate, and early literate adults. In
the same vein, using transcranial magnetic stimulation (TMS)
during identity-based same-different judgments, Nakamura et al.
(2014) demonstrated the causal role of the left occipitotemporal
cortex (comprising the VWFA) in mirror discrimination of
visual words by literate Japanese adults. In their opinion article,
Pegado et al. (2014) set a multisystem learning framework to
answer how mirror discrimination is acquired during learning
to read. They propose that a tight functional link between
the visual and motor systems is crucial for this acquisition.
Finally, given that literacy acquisition also impacts on face
recognition due to competition for neural space (cf. Dehaene,
2009), in an opinion article, Ventura (2014) reviews these
evidence, discusses the possible reasons for this competition, and
proposes new directions considering literacy as a form of visual
expertise.
Taken together, these articles represent an update overview
and demonstrate the diversity of approaches in this research
topic: miscellaneous scientific backgrounds (e.g., neuroscience, in
Nakamura et al., 2014; neuropsychology, in Qian and Bi, 2014;
developmental psychology, in Santi et al., 2015; experimental
psychology; in Kolinsky and Fernandes, 2014), several techniques
(e.g., TMS, Nakamura et al., 2014; behavioral tests, Lachmann
et al., 2014; item response models, Santi et al., 2015), various
written scripts considered (i.e., studies with alphabetic and non-
alphabetic scripts; e.g., Lachmann et al., 2014; Nakamura et al.,
2014, respectively), different populations examined (typical vs.
dyslexic readers, in Qian and Bi, 2014; adults of varying schooling
and literacy levels, in Kolinsky and Fernandes, 2014). These
articles are Dejerine’s legacy as pieces of the (still incomplete)
puzzle on the impact of literacy on visual processing, which
will hopefully contribute to understand the reasons behind this
impact.
Acknowledgments
Preparation of this Research Topic and TF are supported by IF
2013 Program of the Portuguese Foundation for Science and
Technology, FCT (ref IF/00886/2013/CP1194/CT0002). RK is
Research Director of the Fonds de la Recherche Scientifique-
FNRS, Belgium, and her work is supported by the Fonds de la
Recherche Scientifique-FNRS under grant FRFC 2.4515.12 and
by an Interuniversity Attraction Poles grant “IAP 7/33,” Belspo.
We are very grateful to all authors that have contributed to this
research topic.
References
Cohen, L., Dehaene, S., Naccache, L., Lehericy, S., Dehaene-Lambertz, G., Henaff,
M. A., et al. (2000). The visual word form area: spatial and temporal
characterization of an initial stage of reading in normal subjects and posterior
split-brain patients. Brain 123(Pt 2), 291–307. doi: 10.1093/brain/123.2.291
Dehaene, S. (2009). Reading in the Brain: The New Science of How We Read.
New York, NY: Penguin.
Déjerine, J. J. (1892). Contribution à l’étude anatomo-pathologique et clinique des
différentes variétés de cécité verbale. Mém. Soc. Biol. 4, 61–90.
Kolinsky, R., and Fernandes, T. (2014). A cultural side effect: learning to read
interferes with identity processing of familiar objects. Front. Psychol. 5:1224.
doi: 10.3389/fpsyg.2014.01224
Lachmann, T., Schmitt, A., Braet, W., and van Leeuwen, C. (2014). Letters
in the forest: global precedence effect disappears for letters but not
for non-letters under reading-like conditions. Front. Psychol. 5:705. doi:
10.3389/fpsyg.2014.00705
Lachmann, T., and van Leeuwen, C. (2014). Reading as functional
coordination: not recycling but a novel synthesis. Front. Psychol. 5:1046.
doi: 10.3389/fpsyg.2014.01046
Nakamura, K., Makuuchi, M., and Nakajima, Y. (2014). Mirror-image
discrimination in the literate brain: a causal role for the left occpitotemporal
cortex. Front. Psychol. 5:478. doi: 10.3389/fpsyg.2014.00478
Pegado, F., Nakamura, K., Braga, L. W., Ventura, P., Filho, G. N., Pallier, C., et al.
(2014). Literacy breaks mirror invariance for visual stimuli: a behavioral study
with adult illiterates. J. Exp. Psychol. 143, 887–894. doi: 10.1037/a0033198
Polk, T. A., and Farah, M. L. (2002). Functional MRI evidence for an abstract,
not perceptual, word-form area. J. Exp. Psychol. 131, 65–72. doi: 10.1037/0096-
3445.131.1.65
Qian, Y., and Bi, H. Y. (2014). The visual magnocellular deficit in Chinese-
speaking children with developmental dyslexia. Front. Psychol. 5:692. doi:
10.3389/fpsyg.2014.00692
Santi, K. L., Kulesz, P. A., Khalaf, S., and Francis, D. J. (2015). Developmental
changes in reading do not alter the development of visual processing skills: an
application of explanatory item response models in grades K-2. Front. Psychol.
6:116. doi: 10.3389/fpsyg.2015.00116
Ventura, P. (2014). Let’s face it: reading acquisition, face and word processing.
Front. Psychol. 5:787. doi: 10.3389/fpsyg.2014.00787
Warrington, E. K., and Shallice, T. (1980). Word-form dyslexia. Brain 103, 99–112.
Zhou, Y., McBride-Chang, C., and Wong, N. (2014). What is the role of visual skills
in learning to read? Front. Psychol. 5:776. doi: 10.3389/fpsyg.2014.00776
Conflict of Interest Statement: The authors declare that the research was
conducted in the absence of any commercial or financial relationships that could
be construed as a potential conflict of interest.
Copyright © 2015 Fernandes and Kolinsky. This is an open-access article distributed
under the terms of the Creative Commons Attribution License (CC BY). The use,
distribution or reproduction in other forums is permitted, provided the original
author(s) or licensor are credited and that the original publication in this journal
is cited, in accordance with accepted academic practice. No use, distribution or
reproduction is permitted which does not comply with these terms.
Frontiers in Psychology | www.frontiersin.org July 2015 | Volume 6 | Article 985
5
|
OPINION ARTICLE
published: 24July 2014
doi: 10.3389/fpsyg.2014.00776
What is the role of visual skills in learning to read?
Yanling Zhou1*, Catherine McBride-Chang
2and Natalie Wong2
1Department of Early Childhood Education, The Hong Kong Institute of Education, Hong Kong
2Developmental Centre, Department of Psychology, The Chinese University of Hong Kong, Hong Kong
*Correspondence: ylzhou@ied.edu.hk
Edited by:
Tân i a F er n a n d e s, Un i v e rsi t y o f Por t o , Po r t uga l
Reviewed by:
Andrea Facoetti, Università di Padova, Italy
Keywords: reading, visual skill, Chinese, orthography, visual processing
Although the issue of visual skills in
relation to word reading has not been
central to recent explorations of read-
ing development, all visual word reading
involves visual skill. Children constantly
face tasks of differentiating visually sim-
ilar letters or words. For example, dis-
tinguishing “b” from “d,” “a” from “e,”
or “book” from “boot” all require visual
differentiation. Children’s orthographic
knowledge and letter knowledge are causal
factors in subsequent reading develop-
ment in English (e.g., Badian, 1994;
Lonigan et al., 2000). At a pure visual skill
level, some researchers (e.g., Franceschini
et al., 2012)suggestthatcorevisualpro-
cessing skills such as visual spatial atten-
tion in preschoolers could be a causal
factor in subsequent reading acquisition.
In addition, some alphabetic readers with
dyslexia may have visual processing deficits
(e.g., Vald o i s et al . , 2 004 ; Va n d er Lei j
et al., 2013). Following this hypothe-
sis, Franceschini et al. (2013) showed
that action video games that strengthened
children’s visual attention also improved
their reading speed in Italian without
sacrificing reading accuracy, similar to
previous interventional research training
facilitating visuospatial attention skills in
Italian children with dyslexia (Facoetti
et al., 2003). However, orthographic depth
mediates the role of visual attention in
reading (Bavelier et al., 2013; Richlan,
2014). English is a more opaque orthogra-
phy than Italian, and Chinese is even more
opaque than English.
Both eye movement and neuroimag-
ing studies have demonstrated that reading
Chinese affects visual processing dif-
ferently than does reading alphabetic
orthographies (e.g., Inhoff and Liu, 1998;
Perfetti et al., 2010; Szwed et al., 2014).
Inhoff and Liu (1998) found that Chinese
readers used comparatively smaller visual
perceptual spans than English readers.
Szwed et al. (2014) found that readers
of Chinese showed strong activations in
intermediate visual areas of the occipital
cortex; these were absent in French read-
ers. Researchers have attributed these char-
acteristics to perceptual learning resulting
from learning to read Chinese characters
(Rayner, 1998; Perfetti et al., 2010; Szwed
et al., 2014).
Indeed, the role of visual skills for early
reading development may be stronger for
reading Chinese than reading English.
Pure visual skills are sometimes rela-
tively strong correlates of Chinese chil-
dren’s reading (e.g., Huang and Hanley,
1994, 1995; Ho and Bryant, 1997; Siok
and Fletcher, 2001; Mcbride-Chang et al.,
2005; Luo et al., 2013). Such visual tasks
likely tap at least three visual skills that may
be required for Chinese character read-
ing. First, a focus on visual form constancy
(e.g., is this square the same size as the
one embedded in other designs on the
previous page?) likely has some analogies
with the fact that radicals within Chinese
might appear as larger or smaller or even
reversed in appearance across characters.
Second, a focus on visual spatial skills,
i.e., identifying the same form when it
is in a different direction or placed dif-
ferently, might be useful when Chinese
character identification requires children
to reduce a compact character into compo-
nent radicals. Third, visual memory may
be useful in learning to read Chinese in
at least two ways, namely, making asso-
ciations between characters and sounds,
many of which are arbitrary, sometimes
referred to as visual verbal paired associate
learning, and helping children to build a
mental memory of how different radical
parts are located within a character.
What is the evidence that learning to
read Chinese trains one’s visual skills?
Across-culturalstudy(McBride-Chang
et al., 2011b)foundthatChineseand
Korean kindergartners performed signif-
icantly better than Israeli and Spanish
children on a task of visual spatial relation-
ships, the only visual task tested across all
four cultures. Korean kindergartners tend
to learn to read Korean syllables holis-
tically initially, similar to how Chinese
characters are taught. A superior perfor-
mance on visual skills was also found by
Demetriou et al. (2005) for older Chinese
as compared to Greek children. In addi-
tion, Huang and Hanley (1994) found that
both Taiwanese and Hong Kong children
showed a clear advantage on the visual
form discrimination task as compared to
their British peers.
Interestingly, the Chinese written sys-
tem has two versions, the simplified
and the traditional. The simplified script,
which has fewer visual features to distin-
guish one character from another, may
make more visual demands than does
the traditional version. In one study of
those learning to read traditional (in
Hong Kong) as compared to simplified
(in Mainland China) script, those learn-
ing the simplified script outperformed
those learning the traditional one on three
visual tasks, namely visual discrimination,
visual spatial relationships and visual clo-
sure tasks (Mcbride-Chang et al., 2005),
even across time. Peng et al. (2010) found
that electrophysiological response poten-
tials (ERPs) in the brains of those expert
readers who saw characters with one stroke
either added or subtracted in a few mil-
liseconds showed the same basic pattern:
www.frontiersin.org July 2014 | Volume 5 | Article 776 |
6
Zhou et al. Visual skills in learning to read
The brains of simplified script readers
appeared to register the alterations early
in processing; those of traditional script
readers did not.
Importantly, most studies on the topic
of visual skills and word reading were
carried out at a single point in time,
rather than in a longitudinal study, and
there are few experimental studies on this
topic. Thus, the issue of causality is not
clear (e.g., McBride-Chang et al., 2011b;
Yang et al., 2013). However, there is prob-
ably a bidirectional association between
pure visual skills and learning to read
in the early years (e.g., McBride-Chang
et al., 2011b). Future directions in this area
should focus on at least three aspects of
research in order to gain a better under-
standing of the causal associations between
literacy and visual skills. First, more
research should explore how and which
visual skills may promote word reading in
the early grades. Second, researchers can
consider more broadly how learning to
read particular orthographies might facil-
itate given visual skills. Third, an explo-
ration of pure visual skills and word read-
ing could be expanded further to visual-
motor skills and writing.
The issue of how visual skills facilitate
word reading is important to explore in
avarietyoforthographies.Forexample,
Nag (2007, 2011) has presented a model
of orthographically contained vs. exten-
sive orthographies. At the most extensive
level is Chinese, with thousands of pos-
sible characters. At the most contained
level are alphabetic orthographies with sets
of around 24 to 30 letters each. In the
middle, she placed Bengali, Hindi, and
Kannada, each with 400+ possible sym-
bols. Collectively, these are referred to as
the ashkara languages. As with Chinese,
small changes in visual symbols in ashkara
scripts signal potentially large changes in
phonological or meaning representations.
For example, native readers of Arabic are
slower to process it than a second lan-
guage of Hebrew because of differences in
visual complexity (Ibrahim et al., 2002;
Abdelhadi et al., 2011). Even in simple
alphabetic orthographies, young children
might memorize words based on par-
ticular visual features (e.g., M has two
humps; the word “bed” in English actually
looks like a bed). Therefore, it is impor-
tant for researchers to continue to explore
whether and which visual analysis skills
might explain early literacy in diverse
orthographies. Perhaps more varied visual
skills would best explain performances in
ashkara languages and Chinese given their
visual complexities. For this research ques-
tion, the focus is on individual differences
within a group learning to read in a single
orthography.
The second question focuses more on
group differences across orthographies:
Do orthographies facilitate visual flexibil-
ity and analysis in different ways? Perhaps
not only are the visual characteristics of
the orthography important, but the style
of teaching and learning the orthogra-
phy is additionally important for facili-
tating visual skills. For example, although
Korean Hangul is ultimately a relatively
simple alphasyllabary, it is taught initially
to children more in the form of sylla-
bles with different components, such that
children have many different configura-
tions to learn. Perhaps children’s visual
memorization loads would be reduced if
they were taught the basic phonological
rules of Korean first, but this is not the
way in which they are instructed. Future
research should consider both the dimen-
sions of visual demands of the orthog-
raphy and also teaching approaches. For
example, young children are often taught
to read Thai with spaces in between
words indicated before they are gradu-
ally coaxed to read Thai as it is writ-
ten for adults—without spaces between
words. Conceivably, those learning to read
Thai with and without spaces might show
different visual patterns of discrimination
early on. Another area for research on this
topic would be to compare children learn-
ing to read orthographies that differ on the
dimension of contained vs. expansive as
defined by Nag, at least in three aspects,
i.e., alphabetic, ashkara, and Chinese,
across the early years of literacy develop-
ment (perhaps ages 4–7 years) to deter-
mine whether those learning an alpha-
bet are least sophisticated in visual skill,
those learning an ashkara in the middle,
and Chinese learners the best. Although
McBride-Chang et al. (2011b) compared
5-year-olds learning Chinese, Korean, and
alphabets, this study could be expanded to
include ashkara learners and to examine
the developmental trend with age across
several dimensions of basic visual skill.
Athirdissuetoconsidermakesananal-
ogy from word reading and visual recog-
nition, considered above, to word writ-
ing and visual copying. We have recently
established that children who tend to write
Chinese characters better tend also to
show better abilities to copy 2-dimensional
unfamiliar forms (e.g., Wang et al., 2013).
These forms were foreign scripts that were
coded by those unfamiliar with each (e.g.,
aChineseresearchassistantevaluatedchil-
dren’s writing of Hebrew based purely
on the visual representation of the writ-
ing perceived). Unfamiliar scripts were
selected to ensure that the 2-dimensional
writing was equally unfamiliar to all chil-
dren. (In contrast, copying of geometric
shapes or one’s own script would be poten-
tially problematic because those who are
academically more skilled often tend to
write all familiar stimuli better than those
who are less so). Tan et al. (2005) have
suggested that copying skills are impor-
tant for learning to write/spell Chinese.
However, there is very little research that
has examined this question for orthogra-
phies other than Chinese. Vel l ut i no e t a l.
(1975) found that the copying of Hebrew
did not distinguish dyslexic from non-
dyslexic children who were native English
speakers unfamiliar with Hebrew. In con-
trast, such copying skills did distinguish
those with and without dyslexia in Chinese
(McBride-Chang et al., 2011a). However,
few, if any researchers, have gone fur-
ther with this research, examining to what
extent the ability to copy unfamiliar mate-
rials is associated with the ability to write
words in a native orthography. Given
aproposedfirststageofwordreading
as primarily visual (Ehri, 2013), a first
stage of word writing might be, corre-
spondingly, associated with visual-motor
skills that can be measured using pure
two-dimensional patterns. Perhaps such
copying abilities are particularly linked
to learning to write in Chinese or in
ashkara. However, it is important to exam-
ine these abilities independently within,
as well as across, orthographies. While it
may be the case that copying of unfa-
miliar stimuli explains subsequent spelling
skills for Hindi, Chinese, Korean, or
even Dutch children within a group, for
example, it is also interesting to consider
whether learning to read the most expan-
sive orthography of Chinese facilitates
Frontiers in Psychology |DevelopmentalPsychology July 2014 | Volume 5 | Article 776 |
7
Zhou et al. Visual skills in learning to read
superior visuo-motor skills more gener-
ally (as compared to those learning to
read and write Dutch, for example). More
research on the interface between literacy
skills within and across orthographies and
visual and visuo-motor skills, can poten-
tially yield new directions that are theoret-
ically interesting and possibly practically
important.
To co n cl u de , t h e r o l e o f vi s u a l sk i ll s
in learning to read is apparently com-
plex, and our understanding of this role
depends upon the extent to which we look
within as compared to between orthogra-
phies. The types of visual skills, the types
of orthographies, and the teaching meth-
ods for literacy instruction all influence
this association. Moreover, the associa-
tion between visual skills and literacy
development is likely bidirectional. This
association can be expanded to focus
on visuo-motor skills and writing. These
issues cross-culturally represent some new
avenues for future research.
ACKNOWLEDGMENT
This research was supported by the
General Research Fund of the Hong Kong
Special Administrative Region Research
Grants Council (CUHK: 451811) to
Catherine McBride-Chang.
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Conflict of Interest Statement: The authors declare
that the research was conducted in the absence of any
commercial or financial relationships that could be
construed as a potential conflict of interest.
Received: 23 April 2014; accepted: 01 July 2014;
published online: 24 July 2014.
Citation: Zhou Y, McBride-Chang C and Wong N
(2014) What is the role of visual skills in learn-
ing to read? Front. Psychol. 5:776. doi: 10.3389/fpsyg.
2014.00776
This article was submitted to Developmental Psychology,
a section of the journal Frontiers in Psychology.
Copyright © 2014 Zhou, McBride-Chang and Wong.
This is an open-access article distributed under the terms
of the Creative Commons Attribution License (CC BY).
The use, distribution or reproduction in other forums
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www.frontiersin.org July 2014 | Volume 5 | Article 776 |
8
ORIGINAL RESEARCH ARTICLE
published: 31 October 2014
doi: 10.3389/fpsyg.2014.01224
A cultural side effect: learning to read interferes with
identity processing of familiar objects
Régine Kolinsky1,2*and Tânia Fernandes3
1Fond s de la Recherche Scie nti fiqu e-F NRS, Brus sel s, Be lgi um
2Unité de Recherche en Neurosciences Cognitives, Center for Research in Cognition and Neurosciences, Université Libre de Bruxelles, Brussels, Belgium
3Facult y of Psychology, Center fo r Research in Psychology, Universid ade de Lisboa, Li sboa, Portugal
Edited by:
Natasha Kirkham, Birkbeck College,
UK
Reviewed by:
Anna V. Fisher, Carnegie Mellon
University, USA
Joanne Ca therine Tarasuik,
Swinbu rne University of
Tech n o l o g y , Aus t r a l i a
*Correspondence:
Régine Kol insky, Unité de Recherche
en Neurosciences Cognitives,
Université Libre de Bruxelles, CP
191, 5 0, Av. F. Roosev el t, B-105 0
Brussels, Belgium
e-mail: rkolins@ulb.ac.be
Based on the neuronal recycling hypothesis (Dehaene and Cohen, 2007), we examined
whether reading acquisition has a cost for the recognition of non-linguistic visual materials.
More specifically, we checked whether the ability to discriminate between mirror images,
which develops through literacy acquisition, interferes with object identity judgments, and
whether interference strength varies as a function of the nature of the non-linguistic
material. To these aims we presented illiterate, late literate (who learned to read
at adult age), and early literate adults with an orientation-independent, identity-based
same-different comparison task in which they had to respond “same” to both physically
identical and mirrored or plane-rotated images of pictures of familiar objects (Experiment 1)
or of geometric shapes (Experiment 2). Interference from irrelevant orientation variations
was stronger with plane rotations than with mirror images, and stronger with geometric
shapes than with objects. Illiterates were the only participants almost immune to mirror
variations, but only for familiar objects. Thus, the process of unlearning mirror-image
generalization, necessary to acquire literacy in the Latin alphabet, has a cost for a basic
function of the visual ventral object recognition stream, i.e., identification of familiar
objects. This demonstrates that neural recycling is not just an adaptation to multi-use
but a process of at least partial exaptation.
Keywords: visual object recognition, mirror images, enantiomorphy, literacy
INTRODUCTION
According to several theories concerning the functional organiza-
tion of the brain, it is quite common for neural circuits established
for one purpose to be exapted (Gould and Vrba, 1982)ortinkered
(Jacob, 1977)duringevolution(e.g.,themassive redeployment
hypothesis, Anderson, 2007a,b)ornormaldevelopment(theneu-
ronal recycling hypothesis, Dehaene and Cohen, 2007; Dehaene,
2009), so that they may come to serve a different purpose (see
Anderson, 2010,forareview).Theneuronalrecyclinghypothesis
is specifically interested in the acquisition of cultural inventions
such as reading or mathematics that have emerged too recently in
mankind, precluding evolution to have engendered cortical cir-
cuits dedicated to these purposes. Consequently, these cognitive
abilities have to be learned and must find their neuronal niche,
namely pre-existing neural systems “that are sufficiently close
to the required function and sufficiently plastic as to reorient a
significant fraction of their neural resources to this novel use”
(Dehaene and Cohen, 2007,p.384).
Under this hypothesis, cultural learning is generally facili-
tated by pre-existing cortical properties. In the case of reading
acquisition, several characteristics of the ventral visual pathway,
including the general properties for invariant object recognition
(e.g., Serre et al., 2007; Ullman, 2007), may explain why a sub-
part of the left ventral visual system, termed the visual word
form area (VWFA,e.g.,Cohen et al., 2000), has been partially
co-opted or recycled for recognizing the visual shapes of written
symbols.
However, it is quite unlikely that all pre-existing cortical prop-
erties suit the new, target function. In some cases the acquisition
of cultural inventions may require the overcoming of properties
that were useful for the original function, but are deleterious
for the new one. An example of such an undesirable prop-
erty for reading acquisition is mirror-image generalization, also
called mirror invariance,namelythetendencytoconfuselateral
reflections.
Difficulties in differentiating and remembering lateral reflec-
tions or enantiomorphs have been reported in infants (e.g.,
Bornstein et al., 1978; Bornstein, 1982), children (e.g., Gibson
et al., 1962; Rudel and Teuber, 1963; Cronin, 1967; Gibson, 1969;
Casey, 1984; Shepp et al., 1987; de Kuijer et al., 2004), and even
adults (e.g., Butler, 1964; Sekuler and Houlihan, 1968; Standing
et al., 1970; Wolf, 1971; Farrell, 1979; Nickerson and Adams, 1979;
Martin and Jones, 1997; de Kuijer et al., 2004; Rentschler and
Jüttner, 2007), for whom long-term priming (with primes and
probes separated by several minutes) is unaffected by left-right
reflection (e.g., Biederman and Cooper, 1991; Stankiewicz et al.,
1998; Fiser and Biederman, 2001). Mirror invariance seems to
have been deeply rooted by evolution into the visual system: many
animals (e.g., fishes, octopuses, rodents, and monkeys) are also
confused by enantiomorphs (e.g., Sutherland, 1960;seeareview
www.frontiersin.org October 2014 | Volume 5 | Article 1224 |
47
Kolinsk y and Fernandes Literacy, enantiomorphy, and object recognition
in, e.g., Corballis and Beale, 1976), and neurons in the monkeys’
inferotemporal cortex generalize over mirror reversal (Logothetis
and Pauls, 1995; Logothetis et al., 1995; Rollenhagen and Olson,
2000; Baylis and Driver, 2001).
This characteristic of the visual system presumably arose
in the course of evolution because most natural visual cate-
gories are invariant across enantiomorphic changes (Corballis
and Beale, 1976; Gross and Bornstein, 1978), and hence, lat-
eral reversals convey little information about the object viewed:
“a tiger is equally threatening when seen in right or left pro-
file” (Rollenhagen and Olson, 2000,p.1506).However,whereas
useful for the recognition of natural objects, mirror invariance
is deleterious for reading in the Latin alphabet. As this script
includes minimal mirror pairs such as band d,mirrorgener-
alization would impede reading acquisition, leading to confu-
sions between mirrored letters. Mirror invariance is an intrinsic
property of a subpart of the visual cortex that has thus to be
unlearned or at least suppressed so that one can become a fluent
reader.
Consistently, in fluent adult readers the VWFA simultaneously
shows a maximal effect of mirror priming for pictures of famil-
iar objects, fruits, or animals and an absence of mirror priming
for words (Dehaene et al., 2010a)andletters(Pegado et al., 2011).
In an orientation-independent task in which participants had to
judge either whether a target was larger or smaller in real-life than
astandardcomputerscreen(Dehaene et al., 2010a)orwhetherit
stayed (or not) within a central frame (Pegado et al., 2011), each
target being preceded by either the same or a different prime that
appeared either in the same orientation or mirrored, repetition
suppression (i.e., decreased fMRI activation due to processing
subsequent stimuli with identical attributes) was observed in the
VWFA only for mirrored pictures, not for mirrored words or let-
ters. In addition, in Dehaene et al. (2010a),thesizejudgments
were accelerated by mirrored primes much more for pictures than
for words.
At the behavioral level, there is considerable evidence for
aprogressiveunlearningofmirrorinvarianceinchildren,and
this process, crucial for linguistic materials, generalizes to non-
linguistic stimuli (e.g., Gibson et al., 1962; Rudel and Teuber,
1963; Cronin, 1967; Gibson, 1969; Serpell, 1971; Casey, 1984).
These developmental studies confounded age with literacy level,
leading to the view that the ability to discriminate mirror images
would mainly depend on neural maturation (e.g., Orton, 1937;
Corballis and Beale, 1976; Casey, 1984). However, more recent
work on adults disentangled the influence of literacy from that of
neural maturation. In these studies, adults who remained illiterate
for strictly socioeconomic reasons were far poorer at discrimi-
nating between non-linguistic enantiomorphs (of geometric or
blob-like shapes, as well as of pictures of familiar objects like tools,
furniture, and clothes) than both early literates,wholearnedto
read at school in childhood, and late literates,whoneverattended
school in childhood but learned to read in adulthood in special
literacy classes (Kolinsky and Verhaeghe, 2011; Kolinsky et al.,
2011; Fernandes and Kolinsky, 2013). Therefore, it is not neu-
ral maturation, but the need to take enantiomorphic contrasts
into account when learning a script that includes mirrored sym-
bols that pushes one to unlearn (Dehaene et al., 2010a)oratleast
partly inhibit (Duñabeitia et al., 2011; Perea et al., 2011)mirror-
image generalization during explicit, conscious processing of both
linguistic and non-linguistic materials.
In readers, this unlearning process may have adverse conse-
quences for object recognition if objects vary by orientation in
awayirrelevanttothetask.Consistentwiththisideaarethe
priming effects observed by Dehaene et al. (2010a) in the size
judgment task: for pictures of objects, behavioral priming effects
were smaller for mirrored than for identical primes. Similarly,
in a behavioral orientation-independent, identity-based same-
different comparison task in which participants had to respond
“same” to both physically identical and mirror images, Dehaene
et al. reported that participants showed interference from irrel-
evant mirror variations (henceforth, mirror interference): they
were faster to respond to identical than to mirrored images of
non-linguistic objects. Using a similar identity-based task, Pegado
et al. (2014) provided direct evidence supporting the idea that
such mirror interference is a side effect of literacy acquisition:
both early and late literate adults presented slowed responses and
increased error rates when letters strings, false-fonts, and pictures
of familiar objects were mirrored rather than strictly identical,
whereas illiterate adults did not present any cost for mirrored
pairs.
In the present study, we also compared illiterate, late literate
and early literate adults, using an identity-based same-different
comparison task similar to the one used by Dehaene et al. (2010a)
and Pegado et al. (2014):intwoexperiments,oneachtrialpar-
ticipants were asked to decide whether the second stimulus (S2)
was the same or not as the first one (S1), independently of its
orientation. Our aim was two-fold.
First, we checked for the specificity of the literacy effect
reported by Pegado et al. (2014) by comparing the mirror inter-
ference effect to the interference caused by another orientation
contrast, i.e., rotations in the image plane or plane rotations
(henceforth, rotation interference). As already noted by Gibson
et al. (1962), both mirror images and plane rotations distinguish
graphic forms in the Latin alphabet (e.g., d—b, and d—p, respec-
tively). Literacy would thus impact on the ability to discriminate
both types of orientation contrasts. Yet, according to the neu-
ronal recycling hypothesis (Dehaene, 2009), the impact of reading
acquisition should be stronger on enantiomorphy, as the ventral
visual pathway is originally sensitive to plane rotations but not
to mirror images (e.g., Logothetis and Pauls, 1995; Logothetis
et al., 1995). Consistently, in orientation-dependent tasks, both
illiterate and literate adults explicitly discriminate plane rota-
tions far more easily than enantiomorphs (Kolinsky et al., 2011;
Fernandes and Kolinsky, 2013). It is thus probable that in an
identity-based task, (irrelevant) plane-rotation contrasts would
be more automatically activated than (irrelevant) mirror-image
contrasts. Although this difference might hold true for all partici-
pants, whatever their literacy level, it might be particularly strong
for illiterates, as they display very poor enantiomorphic discrim-
ination (Kolinsky and Verhaeghe, 2011; Kolinsky et al., 2011;
Fernandes and Kolinsky, 2013). Here, we thus predicted that the
interference effect would be stronger with plane rotations than
with mirror images for all participants, and that rotation interfer-
ence would be less modulated by literacy than mirror interference,
Frontiers in Psychology |DevelopmentalPsychology October 2014 | Volume 5 | Article 1224 |
48
Kolinsk y and Fernandes Literacy, enantiomorphy, and object recognition
which was expected to be far stronger in literate than illiterate
participants, as was the case in Pegado et al. (2014).
Second, we checked whether the strength of the interference
displayed by the participants would vary as a function of the
nature of the non-linguistic material. Across the two experi-
ments, we examined the impact of familiarity of the material. In
Experiment 1, on familiar objects, we also examined the role of
graspability, namely of the degree by which visuomotor informa-
tion is critical to the representation of the object, by comparing
identity-based judgments for non-graspable and graspable objects;
for the latter (e.g., a hammer), there is a strong relationship
between shape and manner of being grasped or manipulated.
The impact of familiarity of the material was examined by
comparing pictures of familiar objects (Experiment 1) to geo-
metric shapes (Experiment 2). We predicted that interference
from irrelevant orientation variations would be stronger with
geometric shapes than with familiar objects (at least with non-
graspable ones), for both mirror images and plane rotations.
This prediction is based on three non-mutually exclusive rea-
sons. First, simple geometric shapes may be more similar to letters
than familiar objects, and there seems to be an early bias in the
VWFA for processing visual features of symbol-like shapes. In
support of this idea, Szwed et al. (2011) found that configura-
tions of line junctions, which seem universally used in writing
systems worldwide (Changizi et al., 2006;butseediscussionsin
Coltheart, 2014; Dehaene, 2014; Downey, 2014), specifically pro-
mote activation in the ventral fusiform part of the visual system.
As mirrored letters or words are much more differentiated in the
VWFA than mirrored pictures (Dehaene et al., 2010a; Pegado
et al., 2011), if geometric shapes were treated as visual features
of symbol-like shapes, then their mirror images would also be
more differentiated than mirrored familiar objects, hence lead-
ing to stronger mirror interference for geometric shapes in an
identity-based task. An early bias to the processing of this kind
of material might also explain that even in for 4-year-old preliter-
ates, letter-like shapes already activate the VWFA (Cantlon et al.,
2011). In addition, even young preliterate children and illiterate
adults may benefit from minimal exposure to letters and other
symbols. Consistently, illiterate adults with some knowledge of
letters already process letters differently than non-letter stimuli
(Fernandes et al., 2014). Finally, according to some visual models,
novel shapes are coded in a viewpoint-dependent, orientation-
specific way, whereas familiar objects (especially non-graspable
ones) benefit from viewpoint-independent, object-centered rep-
resentations (e.g., Ta r r and Bü l tho f f, 19 9 5 ). The enantiomorphic
performance of illiterate adults is consistent with all these views:
in an orientation-dependent task requiring explicit discrimi-
nation of mirror images, their performance was facilitated for
geometric shapes compared to (non-graspable) familiar objects
(Fernandes and Kolinsky, 2013). Here, we thus expected all
groups to present more mirror and rotation interference with
geometric shapes than with familiar objects.
Our former work using an orientation-dependent task also
showed that enantiomorphic performance was modulated by the
graspability of familiar objects (Fernandes and Kolinsky, 2013).
Action-related information seems to be automatically invoked
by graspable objects like tools, even when there is no action on
the object, as in passive viewing or perceptual tasks (e.g., Tucker
and Ellis, 1998; Creem-Regehr and Lee, 2005). Fernandes and
Kolinsky (2013) manipulated specifically whether the position
of the object in the picture signaled the use of one particular
hand if one would want to grasp it. Although no overt grasping
response was required, enantiomorphic performance was facili-
tated for graspable compared to non-graspable objects, i.e., those
for which the position of the object does not signal the use of one
particular hand. This was the case in all groups (illiterate, late and
early literate adults) and probably reflects that orientation signals
the visuomotor properties of graspable objects, for which these
properties are critical but not to non-graspable ones (Murata
et al., 2000; Valyear et al., 2006; Rice et al., 2007). Therefore, in
Experiment 1, we compared graspable to non-graspable famil-
iar objects, predicting that mirror interference would be stronger
with graspable than non-graspable objects.
Since the identity judgment used in the present study is an
easy task, even for unschooled illiterates (cf. Pegado et al., 2014),
instructions emphasized both accuracy and speed, with the lat-
ter being the principal measure of interest. For both accuracy
and response times (RTs), we compared performance on physi-
cally identical trials, in which both object identity and orientation
were the same, to performance on different-orientations trials,
in which object identity was also the same but S2 was either a
mirror image or a plane rotation of S1. Yet, since we know that
illiterates have difficulties at speeded responses, to which they are
not used to (e.g., Morais and Kolinsky, 2002; Ventura et al., 2007;
Kolinsky et al., 2011), and since they often present quite variable
performance (e.g., Kolinsky et al., 2011), we expected them to dis-
play slower and perhaps less accurate responses than literates. To
control for this overall between-group difference, as in Pegado
et al. (2014) we used a normalized interference index computed,
separately for mirror and for plane-rotation variations, as the
ratio between the RT (or accuracy) difference between different-
orientation and identical trials, using as denominator the sum of
RTs (or accuracy) on different-orientation and identical trials. We
predicted that both late and early literates would present stronger
interference from irrelevant orientation variations than illiterates,
especially with enantiomorphs.
EXPERIMENT 1: IDENTITY JUDGMENTS ON FAMILIAR
OBJECTS
METHOD
Participants
Forty-nine adults were paid for their participation to a larger
battery of tests, including orientation-dependent tasks using the
same materials (see below). According to their schooling and
literacy levels (see below), they were assigned to three groups:
unschooled illiterates, unschooled late literates, and schooled
early literates. The ethical committee of the Psychological and
Educational Sciences Faculty at Université Libre de Bruxelles
approved the study protocol; all participants provided oral
informed consent.
To ch e ck f o r ta sk co mm i tm en t , we fi r st e x am in e d th e Signal
Detection Theory (SDT) d′statistic adapted for same-different
comparison tasks (Macmillan and Creelman, 2005), consider-
ing as hits the correct “different” responses on trials in which
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Kolinsk y and Fernandes Literacy, enantiomorphy, and object recognition
both object identity and orientation were different, and as false
alarms the incorrect “different” responses on identical trials, in
which both object identity and orientation were the same (see
mean correct scores in Table 1,separatelyforeachgroup).Two
illiterates were excluded from further analyses because they prob-
ably have not understood the task: both presented a d′of zero,
while all other participants were quite able to perform the task
with mean d′scores of 4.36 (SD =1.56), 5.74 (SD =1.11), and
6.01 (SD =0.67) for illiterates, late literates and early literates,
respectively.
The final samples included 17 illiterates (12 women), aged
31–74 years (M=56.6), 15 late literates (11 women), aged 19–71
years (M=49.3), and 15 early literates (10 women), aged 27–68
years (M=52.5). Early literates had on average 8 years of school-
ing (SD =3.1). Illiterates were either recruited through non-
governmental agencies or were attending the first lessons (first
2weeks)ofliteracyclasses,duringwhichtheyreceivedonly
information about civil rights and possible courses. Late liter-
ates were engaged in or already had finished the fourth (final)
level of the literacy course. The three groups were from the
same socioeconomic and residential backgrounds and had similar
ages, F<1.
All participants were first presented with letter recognition and
reading (6 words and 6 pseudowords) tests. Illiterates were able
to identify, on average, 8.65 letters out of the 23 letters of the
Portuguese alphabet, and only one of them was able to read a sin-
gle word (M=0.49%). Almost all late literates correctly identi-
fied the 23 letters (M=22.67) and reached at least 83.3% correct
in the reading test (M=95.6%). Except for one participant who
did not recognize one letter, all early literates were perfect in both
the letter recognition (M=22.93) and the reading (M=100%)
tests. In the analyses of variance (ANOVA)onthesescores,the
main effect of group was significant on both letter recognition
and reading performance, F(2,44) =88.88 and =3052.46, respec-
tively, both p<0.00011.Post-hoc tests2showed that late and early
literate adults presented the same level of performance on letter
recognition, both differing from illiterates, both p<0.01. In the
reading test, all groups differed from each other, p<0.05 in all
cases.
In order to evaluate potential cognitive differences, all par-
ticipants were tested with the Mini-Mental State Examination
(MMSE,Folstein et al., 1975). Because this test is known to be
sensitive to educational and (correlated) literacy level (e.g., Crum
et al., 1993), we used MMSE revised scores, recalculating individ-
ual scores after discarding the three items that examine reading,
writing, and arithmetic abilities. This led to similar mean scores
of 23.47 (SD =3.02), 22.47 (SD =1.77), and 23.33 (SD =1.68)
by illiterates, late literates and early literates, respectively, F<1.3
1As usual, for all inferential statistics presented in this study, p<0.05 is
interpreted as a statistically significant result.
2All post-hoc between-group tests reported in the present study correspond to
unequal N HSD tests.
3As expected, when the items examining reading and writing abili-
ties were also taken into account, the group effect became significant,
F(2,44) =20.97, p<0.0001, with illiterates differing from both late and
early literates (M=23.47, 27.47, and 28.33, respectively), both p<0.001.
After the orientation-independent tasks presented here, 38
participants (12 illiterates, 13 late literates, and 13 early liter-
ates) were also tested on orientation-dependent tasks using either
pictures of familiar objects or geometric shapes (for detailed
method and results, see Fernandes and Kolinsky, 2013). In the
orientation-dependent task, the illiterates who were presented
with both types of tasks showed difficulties especially in discrim-
inating mirror images, obtaining 64.8% correct on “different”
trials involving mirror images (64.17% for familiar objects, 65.5%
for geometric shapes) vs. more than 80% correct on “different”
trials involving plane rotations (82.1% for familiar objects, 80.3%
for geometric shapes) and more than 85% correct on “same” trials
(85.8% for familiar objects, 86.8% for geometric shapes).
Material and procedure
Stimuli were black and white pictures of asymmetric real objects.
As explained in detail in Fernandes and Kolinsky (2013), most
were from Snodgrass and Vanderwart (1980),theotherswere
from Bonin et al. (2003).ExamplesarepresentedinFigure 1.
Atotalof36differentobjects(seetheAppendixinFernandes
and Kolinsky, 2013)wasused,halfbeinggraspable,theoth-
ers non-graspable, as assessed by an independent group of
participants (see Fernandes and Kolinsky, 2013). According to
the norms collected by Ventura (2003),thetwocategories
were matched on visual ambiguity, complexity, and familiarity,
all t<1.
For each object, a standard position, corresponding always to
S1, was defined, and for the S2 a mirror image (lateral reflection)
as well as a plane rotation were created, both differing from the
standard by 180◦.
Each trial started with a fixation cross presented in the cen-
ter of the screen for 250 ms, after which S1 was presented during
2000 ms, then a 500ms mask comprising random lines separated
the presentation of S2 from the presentation S1 in order to guar-
antee no involvement of iconic memory in performance. On each
trial, participants were asked to decide as quickly and as accu-
rately as possible whether the second object was the same or not
as the first, independently of its orientation. They thus had to
answer “same” if S2 had the same identity as S1, independently of
whether it had the same orientation (identical trials) or not, and
to answer “different” if S2 had a different identity compared to S1,
also independently of their orientation. As illustrated in Figure 1,
on different-orientation trials, S2 could be either a mirrored or
plane-rotated version of S1. RTs were measured from the onset
of S2 to response onset. Immediately after participants gave their
response another trial began, or if no response was provided the
next trial began after 4750 ms.
Participants were presented with 864 trials, half “same,” half
“different.” Each of the six possible pairs used for a partic-
ular object (see Figure 1)waspresentedtwice,indifferent
blocks. Participants were first presented with six practice trials
to familiarize them with the task. They received feedback on the
correctness of their response only for these trials.
RESULTS
Accuracy and RTs for correct responses were analyzed separately.
For each participant, correct RTs longer or shorter than the grand
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Kolinsk y and Fernandes Literacy, enantiomorphy, and object recognition
Ta b l e 1 | E x p e r i m e n t 1 : M e a n p e r f o r m a n c e i n t h e i d e n t i t y - b a s e d s a m e - d i f f e r e n t c o m p a r i s o n t a s k f o r f a m i l i a r o b j e c t s , p r e s e n te d b y o b j e c t t y p e ,
trial type, and group of participants.
Tr i a l t y p e Graspable objects Non-graspable objects
Expected response Orientation Illiterates Late literates Early literates Illiterates Late literates Early literates
Accuracy (%) Different 84.57 [13.86] 94.49 [5.83] 96.09 [4.33] 86.67 [13.71] 95.42 [5.26] 97.02 [2.83]
Same Identical 87.18 [10.01] 95.93 [4.56] 96.67 [3.37] 86.06 [10.81] 94.27 [7.14] 97.13 [2.53]
Same Mirror 86.82 [9.01] 95.47 [4.00] 96.67 [2.74] 87.18 [8.82] 95.27 [4.08] 96.40 [3.11]
Same Rotation 89.00 [7.78] 94.53 [5.90] 97.00 [2.17] 87.24 [10.16] 94.47 [4.60] 94.47 [3.76]
RTs (ms) Different 102 2 [ 24 3 ] 84 4 [ 277 ] 714 [12 9 ] 10 3 1 [25 4] 84 7 [27 1 ] 709 [13 8 ]
Same Identical 826 [269] 677 [213] 591 [77] 828 [227] 680 [207] 607 [86]
Same Mirror 826 [216] 705 [230] 625 [86] 807 [195] 707 [233] 620 [79]
Same Rotation 837 [179] 741 [236] 641 [80] 850 [191] 752 [260] 632 [71]
Standard deviations in brackets.
FIGURE 1 | Examples of the stimuli used in the “same” and “different” trials of Experiment 1. The critical trials are the three types of “same” trials.
mean plus or less 2.5 SD were removed from further analyses
(less than 3% of the data excluded). In all analyses, RTs for cor-
rect responses were logarithmically transformed and accuracy was
arcsine transformed4.Still,forthesakeofclaritytablesandfigures
present RTs in ms and accuracy in percentages.
Table 1 presents the mean scores for all trial types, separately
for each group. Only the trials in which object identity was the
same were considered in the following analyses. For both RTs
and accuracy, we compared performance on physically identi-
cal trials to performance on trials in which object identity was
also the same but where S2 was either a mirror image or a plane
rotation of S1.
4Given that proportions usually follow a binomial distribution in which
the variance is a direct function of the mean, the arcsine transformation
allowed guaranteeing no violation of the normality assumption necessary for
conducting parametric analyses (e.g., Howell, 2010).
In a first step, we performed two separate ANOVAs, one
on RTs, the other on accuracy, each with group (illiterates;
late literates; early literates) as a between-participants vari-
able and orientation (identical; mirror; rotation) and graspabil-
ity (graspable vs. non-graspable objects) as within-participants
variables.
There was a main effect of group for both RTs, F(2,44) =6.79,
p=0.003, η2
p=0.236, and accuracy, F(2,44) =11.16, p<0.001,
η2
p=0.337. Post-hoc comparisons showed that illiterates were
significantly less accurate and slower than early literates, both
p<0.005, and less accurate, p=0.003, but not slower, p=0.10,
than late literates, whereas late and early literates did not differ
from each other in either analysis, both p>0.30.
No other significant effect was found in the accuracy anal-
ysis, all other F<1, including the main effects of orientation
and of graspability, and the orientation by group interaction.
Graspability did not affect performance on RTs either, F<1.
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Kolinsk y and Fernandes Literacy, enantiomorphy, and object recognition
Yet , o r i en t at i on s t ro n gl y a ff ec t e d p e rf o rm a nc e i n th e R Ts an a l-
ysis, F(2,88) =27.31, p<0.001, η2
p=0.383, in which its effect
was modulated by group, F(4,88) =2.48, p<0.05, η2
p=0.101.
Orientation of the stimulus strongly affected the response speed
of both late literate, F(2,28) =35.27, p<0.001, η2
p=0.716, and
early literate adults, F(2,28) =13.48, p<0.001, η2
p=490. In
contrast, it only slightly and non-significantly modulated the illit-
erates’ response latencies, F(2,32) =2.35, p=0.11, η2
p=0.111.
Whereas illiterates’ responses to mirrored trials were as fast as
those to identical trials, F<1, in the two literate groups, perfor-
mance was slower for mirror images compared to identical trials
[late literates: F(1,28) =9.83, p=0.004; early literates: F(1,28) =
10.56, p=0.003]. For rotations, all groups presented slower
responses compared to both identical trials [illiterates: F(1,44) =
3.95, p=0. 05; late literates: F(1,28) =49.95, p<0.001; early
literates: F(1,28) =22.89, p<0.001] and mirror images [illiter-
ates: F(1,44) =15.32, p<0.005; late literates: F(1,28) =32.26,
p<0.001; early literates: F(1,28) =6.15, p=0.019].
The analyses of the interference indexes (performed without
taking graspability into account, as this factor did not affect
performance) showed, in addition, that illiterates were less sus-
ceptible to irrelevant orientation variations than literates for both
mirror images and (although to a lesser extent) for rotations.
As illustrated in Figure 2,ontheRTinterferenceindex,only
illiterates were unaffected by orientation variations, with both
mirror interference and rotation interference not differing from
zero, t<1andt(16) =1.39, p=0.18, respectively. In contrast,
both literate groups presented significant mirror interference
[late literates: t(14) =3.00, p=0.009; early literates, t(14) =3.41,
p=0.004] and rotation interference [late literates: t(14) =6.63,
p<0.001; early literates: t(14) =5.16, p<0.001]. On the accu-
racy interference index, only early literates showed significant
rotation interference, t(14) =2.33, p=0.035, all other p>0.20.
Since the size of interference was similar for late and early
literates for both mirror images, t<1, and plane rotations,
t(28) =1.61, p=0.12, we contrasted the illiterate group to these
literate participants. Compared to them, illiterate adults clearly
presented weaker mirror interference, t(45) =−2.27, p=0.028,
and somewhat weaker rotation interference, t(45) =−1.96,
p=0.056.
DISCUSSION
Our previous work had shown that breaking mirror general-
ization depends on literacy acquisition in the Latin alphabet
(Kolinsky and Verhaeghe, 2011; Kolinsky et al., 2011; Fernandes
and Kolinsky, 2013). Here, similarly to former studies (Dehaene
et al., 2010a; Pegado et al., 2011), we demonstrated that in
adult readers enantiomorphy is automatically evoked during
object recognition. In addition, confirming the results reported
by Pegado et al. (2014),weshowedthatthisprocessisaconse-
quence of literacy acquisition: in an identity-based same-different
comparison task in which participants had to respond “same” to
both physically identical and differently oriented pictures of the
same object, only literate but not illiterate adults were affected by
irrelevant enantiomorphic variations. Thus, in literates, breaking
mirror invariance interferes with a non-linguistic object recogni-
tion task when orientation is neither relevant nor useful for it.
FIGURE 2 | Mean value of the interference index for familiar objects,
computed on accuracy scores (Panel A) and on RTs (Panel B),
separately for each group of participants. Error bars represent standard
error of the mean.
Furthermore, as predicted by the neuronal recycling hypothesis
(Dehaene and Cohen, 2007; Dehaene, 2009), rotation interfer-
ence was stronger than mirror interference, at least in literates.
Mirror-image contrasts thus remain less salient or less automat-
ically evoked than plane rotations, when processing the identity
of familiar objects, probably because enantiomorphy is learned
in the course of literacy acquisition. However, contrary to our
prediction, no effect of graspability was observed.
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Kolinsk y and Fernandes Literacy, enantiomorphy, and object recognition
EXPERIMENT 2—IDENTITY JUDGMENTS ON GEOMETRIC
SHAPES
METHOD
Participants
Among the participants of Experiment 1, 46 participated in this
experiment: 16 illiterates, and all the late and early literates. As in
Experiment 1, we first checked for task commitment, examining
the SDT d′scores in the same-different comparison task. One illit-
erate who presented a d′∼0 was excluded from further analyses.
All other participants were able to correctly perform the task with
mean d′scores of 3.95 (SD =1.93), 4.92 (SD =0.99), and 5.17
(SD =0.92) by illiterates, late and early literates, respectively.
The final illiterate sample thus included 15 participants
(10 women), aged 31–74 years (M=56.0). They were able to
identify, on average, 8.3 letters out of the 23 letters of the
Portuguese alphabet, and none was able to read a single word of
the reading test. Their mean revised MMSE score was 23.80 (SD:
3.14; same score as the unrevised one).
Material and procedure
Nine asymmetric geometric shapes were used as S1 (see examples
in Figure 3).
Construction of the pairs and trial types were identical to
Experiment 1 (see Figure 3). Participants were presented with a
total of 216 trials, half “same,” half “different.” Each S1 shape was
paired four times with a replica and four times with its mirror
image and with its plane rotation. For “different” trials, each S1
shape was paired four times with a different geometric shape, with
a mirror image, and with a plane rotation of that shape.
Procedure was the same as in Experiment 1.
RESULTS
Data were trimmed (<3% of data excluded) and analyzed as in
Experiment 1. Table 2 present the mean scores for all trial types,
separately for each group.
In the ANOVA on accuracy, only the main effect of orien-
tation was significant, F(2,84) =14.83, p<0.001, η2
p=0.261,
with identical trials leading to better performance than both mir-
ror images, F(1,42) =12.43, and rotations, F(1,42) =25.59, both
p≤0.001 (mirror images vs. rotations: F=3.79, p=0.058).
The group effect only tended toward significance, F(2,42) =2.87,
p=0.068, η2
p=0.120. Although the interaction between group
and orientation was not significant, F=1.2, we further exam-
ined the effect of orientation on performance of each group,
considering both the results of Experiment 1 and prior results
on literate participants showing that they are more sensitive to
orientation variations than illiterates (Pegado et al., 2014). In
fact, whereas no effect of orientation was found in illiterates,
F(2,28) =1.76, p=0.19, the effect of orientation was signifi-
cant for both late literates, F(2,28) =6.82, p=0.003, and early
literates, F(2,28) =9.17, p<0.001. In the two literate groups,
relative to identical trials, performance was worse for mirror
images [late literates: F(1,14) =5.32, p=0.036; early literates,
F(1,14) =12.36, p=0.003], and for plane rotations [late liter-
ates: F(1,14) =10.36, p=0.006; early literates: F(1,14) =12.11,
p=0.001]. Consistently, the analyses of the accuracy inter-
ference indexes (see Figure 4A)showedthatonlytheliterates
were penalized by orientation variations, with significant mirror
interference [late literates: t(14) =2.22, p=0.043; early literates:
t(14) =2.14, p=0.049] and rotation interference [late literates:
t(14) =2.77, p=0.015; early literates: t(14) =2.94, p=0.010]. In
contrast, illiterates exhibited no mirror interference, t<1, nor
rotation interference, t(14) =1.40, p=0.18. Since the amount
of mirror and rotation interference was similar for late and
early literates, both t<1, we tested whether illiterates presented
weaker interference than the literate participants. This was the
case for mirror interference, t(42) =−1.80, p=0.038, but not for
rotation interference, t(42) =−1.18, p=0.122.
Yet , t he RT a n al y si s s ug g e s ted t ha t e ven i ll i ter ate s wer e s om e -
what sensitive to irrelevant mirror images of geometric shapes:
both the main effect of group, F(2,42) =5.02, p=0.01, η2
p=
0.193 (with illiterates overall slower than late and early liter-
ates, p<0.05, and p=0.01, respectively), and of orientation,
F(2,84) =26.8, p<0.001, η2
p=0.389, were significant, but not
their interaction, F<1. Contrary to what was observed on accu-
racy, the effect of orientation was significant in all groups [illit-
erates: F(2,28) =4.56, p=0.02; late literates: F(2,28) =14.45,
p<0.001; early literates: F(2,28) =24.83, p<0.001]. Across
groups, performance was the slowest for rotations compared to
identical trials, F(1,42) =36.54, and to mirror images, F(1,42) =
13.14, both ps<0.001, and was also slower for mirror images
than for identical trials, F(1,42) =24.80, p<0.001. Thus, in
terms of latency both illiterate and literate participants dis-
played mirror and rotation interference. The same conclusion
can be drawn from the analysis of the RT interference index: as
illustrated in Figure 4B,mirrorandrotationinterferenceeffects
were significant in all three groups (all p≤0.03). No difference
between illiterate and literate participants was observed, neither
for mirror interference, t(43) =1.05, p=0.300, nor for rotation
interference, t(43) =−0.25, p=0.803.
DISCUSSION AND CROSS-EXPERIMENTS ANALYSES
Contrary to what was observed in Experiment 1 with familiar
objects, here with geometric shapes all participants, whatever
their literacy level, were sensitive to the irrelevant orientation
variations, at least on response latencies and mostly for plane
rotations.
To ch e ck f o r t h e ro b us t ne s s o f t hi s m at e r i al d i ff e re n ce , w e
performed cross-experiment analyses on the accuracy and RT
interference indexes of the 43 participants (13 illiterates, 15 late
literates, 15 early literates) who were presented with both mate-
rials and adequately performed the identity-based task. There
was a significant main effect of material in both analyses, accu-
racy, F(1,40) =10.31, p=0.003, η2
p=0.205, RT, F(1,40) =8.37,
p=0.006, η2
p=0.173, with an overall stronger interference effect
with geometric shapes than with familiar objects. The main effect
of orientation was also significant in both analyses, accuracy,
F(1,40) =7.04, p=0.01, η2
p=0.150, and RT, F(1,40) =24.42,
p<0.001, η2
p=0.379, with overall stronger rotation than mirror
interference. The interaction between material and orientation
was only significant in accuracy, F(1,40) =7.68, p=0.008, η2
p=
0.161, not on RTs, F<1: rotation interference was stronger
with geometric shapes than with familiar objects, F(1,40) =17.64,
p<0.001, whereas mirror interference was similar with both
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Kolinsk y and Fernandes Literacy, enantiomorphy, and object recognition
FIGURE 3 | Examples of the stimuli used in the “same” and “different” trials of Experiment 2. The critical trials are the three types of “same” trials.
Ta b l e 2 | E x p e r i m e n t 2 : M e a n p e r f o r m a n c e i n t h e i d e n t i t y - b a s e d s a m e - d i f f e r e n t c o m p a r i s o n t a s k f o r g e o m e t r i c s h a p e s , p re s e n t e d by t r i a l t y p e
and group of participants.
Tr i a l t y p e Illiterates Late literates Early literates
Expected Orientation
response
Accuracy (%) Different 80.17 [20.08] 92.09 [7.56] 94.13 [4.68]
Same Identical 83.67[19.63] 95.00 [5.24] 95.80 [7.16]
Same Mirror 83.67 [15.67] 91.53 [7.69] 92.27 [6.24]
Same Rotation 80.87 [19.14] 88.53 [10.12] 90.67 [9.62]
RTs (ms) Different 119 4 [ 3 01 ] 960 [232] 836 [218]
Same Identical 941 [322] 734 [138] 723 [136]
Same Mirror 103 4 [37 5 ] 800 [155] 74 7 [ 1 5 5 ]
Same Rotation 1055 [ 3 04] 863 [211] 815 [168]
Standard deviations in brackets.
materials, F(1,40) =1.77, p=0.191. In neither analysis did group
interact with any other factor, all ps>0.10. Thus, in compari-
son to familiar objects, identity-based judgments on geometric
shapes were more strongly affected by irrelevant plane rotations,
whatever the literacy level of the participant.
Given that 38 of the participants of the present study
had also performed orientation-dependent tasks with the same
materials (Fernandes and Kolinsky, 2013), we next examined
whether there was any association between the interference
effects reported here and the performance level observed for
either mirrored or rotated trials in the orientation-dependent
tasks by Fernandes and Kolinsky (2013). Across materials, no
correlation was observed between this performance and the
RT interference index, all rs<0.195, ps>0.24, but when
accuracy was considered, there was a significant correlation
between enantiomorphic performance and mirror interfer-
ence, r(36) =0.387, p=0.016, but not between plane rotation
discrimination and rotation interference, r(36) =−0.176, p=
0.289. Thus, the better the participants discriminated mirror
images, the stronger these interfered on their identity-based
judgments.
GENERAL DISCUSSION
Literacy is an acculturation process that enables massive cognitive
gains. However, according to the neuronal recycling hypothesis
(Dehaene and Cohen, 2007; Dehaene, 2009), this new cultural
ability may compete with evolutionary older functions, lead-
ing to collateral effects. As a matter of fact, enantiomorphy,
namely the ability to discriminate between mirror images that
develops through reading acquisition (Kolinsky and Verhaeghe,
Frontiers in Psychology |DevelopmentalPsychology October 2014 | Volume 5 | Article 1224 |
54
Kolinsk y and Fernandes Literacy, enantiomorphy, and object recognition
FIGURE 4 | Mean value of the interference index for geometric shapes,
computed on accuracy scores (Panel A) and on RTs (Panel B),
separately for each group of participants. Errors bars represent standard
error of the mean.
2011; Kolinsky et al., 2011; Fernandes and Kolinsky, 2013), col-
lides with the original mirror invariance property of the ventral
visual system. Therefore, in the present study we investigated
whether enantiomorphy interferes with object identity judg-
ments, as suggested by former work (Dehaene et al., 2010a;
Pegado et al., 2011, 2014). In particular, we examined whether
the expected mirror interference reflects a specific impact of
literacy on enantiomorphy rather than a general impact on
orientation processing during object recognition. Furthermore,
we also checked whether the strength of the interference displayed
by illiterate and literate adults would be modulated by the famil-
iarity of the material and, for familiar objects, by their graspability
(Fernandes and Kolinsky, 2013). To these aims we presented illit-
erate, late literate (who learned to read at adult age) and early
literate adults with an identity-based same-different comparison
task in which they had to respond “same” to physically identical,
mirrored, and plane-rotated images of either pictures of familiar
objects (Experiment 1) or geometric shapes (Experiment 2). We
examined the interference from irrelevant orientation variations
separately for mirror images and plane rotations.
With pictures of familiar objects, contrary to literate adults,
illiterates did not display any mirror interference. As expected,
for all groups, interference was stronger with geometric shapes
than with familiar objects. With geometric shapes, both plane
rotations and enantiomorphic variations affected response laten-
cies, irrespective of the participants’ literacy level. Still, in terms
of accuracy, contrary to literates, illiterates did not display mir-
ror interference with geometric shapes, whereas they did show
rotation interference.
In what regards familiar objects’ graspability, namely the
degree by which visuomotor information is critical to the repre-
sentation of the object, in contrast to our prediction, this property
had no impact on identity-based judgments. This result pat-
tern stands in sharp contrast to that found by Fernandes and
Kolinsky (2013) in an orientation-dependent task. There, the
explicit discrimination of orientation variations, either mirror
images or plane rotations, was facilitated for graspable objects.
Note, however, that the orientation variations that could have
invoked action-related information of graspable objects were in
the present study irrelevant to the task. Prior studies have shown
that the visuomotor properties of objects are especially processed
by the dorsal, vision-for-action stream (e.g., Va l ye ar et a l . , 200 6 ;
Rice et al., 2007). In particular, parietal regions, part of the dor-
sal stream, have been shown to be critical for processing spatial
attributes of objects in orientation-based tasks, but not their iden-
tity (Harris et al., 2008). Therefore, although both ventral and
dorsal streams operate simultaneously during visual processing,
their relative involvement depends on the specific task. Task speci-
ficities might thus explain the apparent discrepancy between the
graspability effects found in the orientation-based task used by
Fernandes and Kolinsky and their absence in the identity-based
task of the present study. Further brain-imaging studies could test
this possibility.
More importantly, the present result pattern is in line with
prior studies showing that the discrimination of mirror images
and of plane rotations are supported by at least partially different
mechanisms (e.g., Turnbull et al., 1997; Turnbull and McCarthy,
1997), and that the ventral visual pathway is originally sensitive
to plane rotations but not to mirror images (e.g., Logothetis and
Pauls, 1995). In this vein and in line with our prediction, across
groups and experiments, plane rotations interfered more on iden-
tity judgments than mirror images. Furthermore, it was only for
mirror images that the size of the interference effect was linked to
the participants’ enantiomorphic performance in an orientation-
dependent task (cf. Fernandes and Kolinsky, 2013): the better
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55
Kolinsk y and Fernandes Literacy, enantiomorphy, and object recognition
they could discriminate mirror images, the stronger the mirror
interference on their identity-based judgments.
The process of unlearning mirror invariance, necessary to
acquire literacy in the Latin alphabet, has thus a cost for object
identification, a basic function of the visual ventral stream. The
observation of a negative side effect of a literacy-related ability,
namely enantiomorphy, was expected under the neuronal recy-
cling hypothesis (Dehaene and Cohen, 2007; Dehaene, 2009),
which proposes that reading, as other recent cultural inventions,
capitalizes on evolutionary older functions, with which they may
compete. Brain-imaging data had already shown that literacy
induces a profound reorganization of the cortical networks for
vision and language, and that this process involves competition
for neural space in the left fusiform gyrus, especially between
written strings and faces (Dehaene et al., 2010b).
A functional cost like the one reported here is also expected
if some properties that were useful for the original function are
deleterious for the new function, and hence, should be unlearned.
As a direct consequence, this unlearning process would benefit
the new function (here, reading) but harm the older one.
Effects of both neural competition (Dehaene et al., 2010b)and
functional competition as shown here, as well by Dehaene et al.
(2010a) and Pegado et al. (2011, 2014),thusdemonstratethat
neural recycling is not just an adaptation to multi-use (see
discussion in, e.g., Jungé and Dennett, 2010)butaprocessof
at least partial exaptation. More generally, as noted by Dehaene
(2013),thepresenceofmirrorinvariancepriortoliteracyandits
reduction during reading acquisition show that learning to read
involves the recycling of a preexisting circuit that did not evolved
purposely for reading, but adapts to this novel task.
ACKNOWLEDGMENTS
This work was supported by the Fonds de la Recherche
Scientifique-FNRS under grant FRFC 2.4515.12 and by
an Interuniversity Attraction Poles grant IAP 7/33, Belspo
(“Mechanisms of conscious and unconscious learning”). The
first author is Research Director of the Fonds de la Recherche
Scientifique-FNRS, Belgium. The second author is Research
Associate of Fundação para a Ciência e a Tecnologia, FCT,
Investigador FCT 2013 Program (ref IF/00886/2013).
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Conflict of Interest Statement: The authors declare that the research was con-
ducted in the absence of any commercial or financial relationships that could be
construed as a potential conflict of interest.
Received: 01 April 2014; accepted: 09 October 2014; published online: 31 October 2014.
Citation: Kolinsky R and Fernandes T (2014) A cultural side effect: learning to read
interferes with identity processing of familiar objects. Front. Psychol. 5:1224. doi:
10.3389/fpsyg.2014.01224
This article was submitted to Developmental Psychology, a section of the journal
Frontiers in Psycholog y.
Copyright © 2014 Kolinsky and Fernandes. This is an open-access article distributed
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www.frontiersin.org October 2014 | Volume 5 | Article 1224 |
57
ORIGINAL RESEARCH ARTICLE
published: 21 May 2014
doi: 10.3389/fpsyg.2014.00478
Mirror-image discrimination in the literate brain: a causal
role for the left occpitotemporal cortex
Kimihiro Nakamura1,2*, Michiru Makuuchi
2and Yasoichi Nakajima2
1Human Brain Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan
2National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan
Edited by:
Tân i a F er n a n d e s, Un i v e rsi t y o f Por t o ,
Portug al
Reviewed by:
Jon Andon i Dunabeitia, Basque
Center on Cognition, Brain and
Language, Spain
Marcin Szwed, Jagiellonian
University, Poland
*Correspondence:
Kimihiro Nakamura, Human Brain
Research Center, Gradua te School
of Medicine, Kyoto University, 54
Shogoin, Kyoto 606-8057, Japan
e-mail: nakamura.kimihiro.4w@
kyoto-u.ac.jp
Previous studies show that the primate and human visual system automatically generates
acommonandinvariantrepresentationfromavisualobjectimageanditsmirror
reflection. For humans, however, this mirror-image generalization seems to be partially
suppressed through literacy acquisition, since literate adults have greater difficulty in
recognizing mirror images of letters than those of other visual objects. At the neural
level, such category-specific effect on mirror-image processing has been associated with
the left occpitotemporal cortex (L-OTC), but it remains unclear whether the apparent
“inhibition” on mirror letters is mediated by suppressing mirror-image representations
covertly generated from normal letter stimuli. Using transcranial magnetic stimulation
(TMS), we examined how transient disruption of the L-OTC affects mirror-image recognition
during a same-different judgment task, while varying the semantic category (letters and
non-letter objects), identity (same or different), and orientation (same or mirror-reversed)
of the first and second stimuli. We found that magnetic stimulation of the L-OTC produced
asignificantdelayinmirror-imagerecognitionforletter-stringsbutnotforotherobjects.
By contrast, this category specific impact was not observed when TMS was applied to
other control sites, including the right homologous area and vertex. These results thus
demonstrate a causal link between the L-OTC and mirror-image discrimination in literate
people. We further suggest that left-right sensitivity for letters is not achieved by a local
inhibitory mechanism in the L-OTC but probably relies on the inter-regional coupling with
other orientation-sensitive occipito-parietal regions.
Keywords: mirror-image discrimination, transcranial magnetic stimulation, visual orientation invariance,
occipitotemporal cortex, visual word-form area
INTRODUCTION
The human and primate ventral visual system is known to sponta-
neously generate a common and invariant representation from a
visual object image and its mirror reflection, irrespective of their
left-right orientation (Eger et al., 2004; Vuilleumier et al., 2005;
Dehaene et al., 2010b; Freiwald and Tsao, 2010). For humans,
this mirror-image generalization probably relies on a fast neu-
ral process occurring at ∼200 ms after stimulus onset (Eddy and
Holcomb, 2009), but seems to be partially “suppressed” through
literacy acquisition. That is, literate adults are known to have
greater difficulty in recognizing mirror images of letters than
those of other objects, whereas this is not the case for illiterate
people (Kolinsky et al., 2011; Pegado et al., 2014). Recent func-
tional magnetic resonance imaging (fMRI) data show that such
category-specific sensitivity in mirror-image processing relies on
the left visual word-form area (VWFA) in the left fusiform gyrus
(Dehaene et al., 2010a,b; Pegado et al., 2011).
However, it remains unclear how the strong behavioral sensi-
tivity to letter/word orientation is achieved in this and adjacent
left occpitotemporal cortex (L-OTC). More specifically, while this
region is thought to represent abstract shape-invariant identi-
ties of letters (see Dehaene et al., 2005 for review, and see also
Rothlein and Rapp, 2014), it is unknown whether the same region
comprises a local inhibitory circuit for suppressing mirror-image
generalization only for letters and words. More specifically, it
is possible that mirror-image representations are covertly gen-
erated even from letter stimuli and then suppressed via a local
feedback circuit in the L-OTC. This is expected because (1) a
recent event-related study has shown that early neural responses
to masked letters/words (i.e., ∼250 ms after stimulus onset) do
not differ between normal-oriented and mirror-reversed stim-
uli (Dunabeitia et al., 2011), and (2) such lateral inhibition
of non-canonical inputs seems to reflect an ubiquitous feature
of the neural mechanism involved in early sensory processing
(Srinivasan et al., 1982)andplayaroleinshapingresponsetuning
of higher-order sensory pathways (Carandini and Heeger, 2012).
Indeed, human extrastriate cortex may comprise a lateral inhibi-
tion mechanism in which neuronal populations responsive to one
stimulus category suppress those responsive to another category
(Allison et al., 2002). It is therefore plausible that a category-
specific inhibitory circuit for mirror-reversed letters develops
within the L-OTC through literacy training.
On the other hand, it is also possible that the L-OTC comprises
no such orientation-sensitive inhibitory mechanism for mirror-
image discrimination. This is because this region per se has
been associated with abstract, shape- and orientation-invariant
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Nakamura et al. Mirror-image discrimination in the left occipitotemporal cortex
representations of visual stimuli (Dehaene et al., 2005)andthus
might be unable to differentiate their left-right orientations. If
this is the case, mirror-image discrimination during visual word
perception may not occur inside the L-OTC, but rather rely on
input signals from other orientation-sensitive regions, such as
the lateral occipital cortex (LOC) (Eger et al., 2004; Vuilleumier
et al., 2005; Dilks et al., 2011)andposteriorparietalcortex(PPC)
involved in spatial recognition (Poldrack and Gabrieli, 2001).
In the present study, we examined these two possibilities by
applying transcranial magnetic stimulation (TMS) to the left and
right OTC during a same-different judgment task (Figure 1A).
We mea s u red a be h av io r a l imp a ct of TM S o n m irr o r - imag e r e cog-
nition by varying the semantic category (letters and non-letter
objects), identity (same or different) and orientation (same or
mirror-reversed) of the first and second stimuli. Crucially, the
two different models described above should predict different
patterns of TMS-induced interference during mirror-image pro-
cessing. On one hand, if the L-OTC comprises a category-specific
inhibitory circuit for left-right discrimination, the visual recog-
nition of mirror-reversed words should be facilitated when this
region is disrupted by TMS. That is, a transient reduction of
inhibitory signals is likely to accelerate the otherwise suppressed
mirror-image processing for letter-strings, since mirror general-
ization is known to occur in both hemispheres (Eger et al., 2004;
Vuilleumier et al., 2005; Freiwald and Tsao, 2010). On the other
hand, if such local inhibition is not operating in the L-OTC, no
behavioral facilitation should occur during mirror-image recog-
nition when TMS is applied to this region. Rather, magnetic
stimulation of the region would disrupt the orientation-invariant
representations of stimulus identity, and thereby induce a delay
in same-different judgment about mirror images. These effects
should be strictly category-specific, i.e., detectable only for word
stimuli and not for other visual objects.
MATERIALS AND METHODS
PARTICIPANTS
Twelv e r igh t -ha n d ed Jap a nese s p eake r s par t ici p a ted i n t h e pre s e nt
TMS experiment (age range 20–38 years, six females). All of
them gave written informed consent prior to the TMS experi-
ment. We additionally recruited a separate group of 18 Japanese
participants (age range 19–45 years, seven females) for a con-
trol experiment without TMS (see Results). The protocol of this
study was approved by the institutional ethical committee at the
National Rehabilitation Center for Persons with Disabilities.
MATERIALS AND PROCEDURES
Visual stimuli consisted of 48 Japanese words written in a syl-
labic script (katakana) and 96 black-and white drawings of objects
(e.g., animals, clothes, faces, tools). Since printed words and other
drawings greatly differ in physical features, it is possible that they
also depart from each other in the degree of asymmetry. We there-
fore assessed the degree of asymmetry for the present stimuli
using a pixel-based analysis. That is, visual images were bina-
rized to remove white background pixels and then edge-detected
using the Matlab image processing toolbox (Mathworks, USA),
For each item, we determined the number of overlapping pix-
els shared by the filtered image and its left-right reversal, and
FIGURE 1 | Behavioral task and cortical target regions. (A) Sequence of
visual stimuli. Each trial comprised central fixation, a first stimulus (S1),
central fixation, a second stimulus (S2) followed by a response period.
Visual st imuli for S1 and S2 were either identical or different images taken
from the same category and presented either in the same or mirror
reversed orientation. Participants responded by key-press as quickly and
accurately as possible to decide whether or not paired stimuli were
identical regardless of their orientation. (B) Locati ons of the cortical target
structures in the occipitotemporal areas. The average coordinates of these
cortical targets across participants were x=−62, y=−60, z=−5forthe
L- O T C a n d x=61, y=−57, z=−5fortheR-OTC.
computed the ratio of overlap against the whole filtered image.
This analysis revealed that mean percentage overlap (SD) was 11.6
(5.7)% for words and 9.52 (3.99)% for objects, respectively, and
did not differ from each other (p>0.2, Wilcoxon rank-sum test).
In addition, faces tended to be slightly more symmetrical than
other non-face objects (10.1 (3.8) and 8.9 (4.1)%, respectively),
but this difference neither reached significance (p=0.18). These
results thus confirmed no significant difference in the degree of
asymmetry between words and other objects.
Each trial comprised central fixation, a first stimulus (S1), cen-
tral fixation, a second stimulus (S2) followed by a response period
(Figure 1A). Visual stimuli for S1 and S2 were either identical
or different images taken from the same category and presented
either in the same or mirror reversed orientation. Participants
responded by key-press as quickly and accurately as possible to
decide whether or not paired stimuli were identical regardless of
their orientation (thus they should make a “same” response when
S2 was a mirror image of S1). Each participant received two ses-
sions of 240 randomly ordered trials. The order of the stimulation
site was counterbalanced across participants. The experiment was
therefore arranged in a 2 ×2×2×2 factorial design, treating
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Nakamura et al. Mirror-image discrimination in the left occipitotemporal cortex
S1–S2 stimulus identity (same vs. different), orientation (same vs.
mirror-flipped), category (words vs. objects), and magnetic stim-
ulation site (L-OTC vs. R-OTC) as within-participant factors. In
addition, we performed a third 240-trial session in nine of the
12 participants to assess a non-specific, global impact of TMS
by applying the same level of magnetic pulse to a distant control
region, i.e., the vertex (Vx, see Results).
TMS PROCEDURES
Ahigh-resolutionanatomicalMRIwasobtainedforeachpar-
ticipant prior to the TMS experiment. We selected the left and
right OTC as target structures to assess the regional specific effects
of TMS on mirror-image recognition. For the L-OTC stimula-
tion, we targeted a posterior part of the left inferolateral temporal
region ∼25 mm posterior to the lateral edge of the transverse tem-
poral gyrus, which overlaps the a subpart of the L-OTC known
as the VWFA (Dehaene et al., 2005). On each participant’s MRI,
a right homologous region was identified as a target structure
in the R-OTC. The average coordinates of these cortical tar-
gets across participants were x=−62, y=−60, z=−5forthe
L-OTC and x=61, y=−57, z=−5fortheR-OTC(Figure 1B)
according to the standardized brain space defined by the Montreal
Neurological Institute. In addition, the Vx was selected as an
active cortical control site for each participant.
Asingle-pulseTMSwasgeneratedusingtwoMagStim200
magnetic stimulators connected to a 70mm figure-of eight coil
through a BiStim module (Magstim, UK). The coil was kept tan-
gential to the skull for stimulating the OTC and Vx with the
handle pointing backward parallel to the midline. TMS pulse was
applied 100 ms prior to the onset of S2 at an intensity of 60% of
the stimulator power output, which corresponded to 80∼120%
of the motor threshold of resting hand muscles. A single mag-
netic pulse at this stimulus intensity is estimated to suppress the
local neuronal activity for approximately 100∼200 ms (Moliadze
et al., 2003). Using a 3D-navigation system (Nexstim, Finland),
we tracked the position and orientation of the coil relative to the
head at the rate of ∼20 Hz to minimize their mutual displacement
during the TMS session using our standard TMS procedures (see
Nakamura et al., 2006, 2010).
RESULTS
EFFECTS OF TMS ON THE LEFT AND RIGHT OCCIPITOTEMPORAL
REGION
Participants made only few errors during the same-different judg-
ment task [mean error rate (SD)=2.81 (1.91)%]. We assessed
reaction time data for correct responses (Figure 2) using 2 ×2×
2×2ANOVAtreatingsite(L-OTCvs.R-OTC),category(words
vs. objects), orientation (same vs. mirror-reversed) and identity
(same vs. different) as within-participant factors (outliers >3SD
above the mean were excludedfrom this and all subsequent analy-
ses). First, overall latency did not differ between words and objects
(F<1). However, participants responded 28 ms more slowly in
L-OTC stimulation than in R-OTC stimulation, whereas this left-
right difference in TMS was significant (p=0.003). These effects
interacted with each other (p<0.02), suggesting that the left-
right asymmetry in TMS effects was greater for words (35ms)
than for objects (20 ms).
FIGURE 2 | Behavioral effects induced by the TMS of the left and right
OTC. For each TMS site, m ean r eac tion times d uri ng same-differe nt
judgment are illustrated with respect to the identity, category, and
orientation of visual stimuli. For each site, participants responded similarly
when S1 and S2 differed in identity from each other (i.e., “different” trials)
irrespective of their category and orientation. In same-identity trials,
however, participants responded more slowly when S1 and S2 were mirror
images than when they were identical. Moreover, this mirror recognition
cost was greater for words than for objects when TMS was applied to the
L- O T C , w h e r e a s n o s u c h c a t e g o r y - s p e c i fi c e f fe c t e m e r g e d w h e n T M S w a s
applied to the R-OTC.
On the other hand, participants responded 33 ms more slowly
in mirror trials than in same trials. This effect of orientation was
highly significant (p<0.001), but interacted with the effect of
category (p<0.02), suggesting that the behavioral cost of mir-
ror recognition was greater for words (41 ms) than for objects
(25 ms). Furthermore, the main effect of identity was also sig-
nificant (p=0.004) and interacted with that of orientation
(p<0.001), suggesting a net component of cognitive process-
ing cost for recognizing mirror images as being identical. Indeed,
the effect-size of identity was much greater when paired stim-
uli were in the same orientation (56 ms) than in mirror-flipped
orientation (3 ms). This finding was expected because the orien-
tation difference between S1 and S2 should yield a recognition
cost in making “same” responses only when the stimuli are mir-
ror images, whereas the orientation of stimuli is not important
in making “different” responses when S1 and S2 are totally dif-
ferent images (we therefore performed further analysis restricted
to same identity trials, as described below). These effects of iden-
tity and orientation produced no triple interaction, either with
site (p>0.1) or with category (F<1), but showed a significant
quadruple interaction with site and category (p=0.04). This last
finding suggests that the recognition cost for assimilating mir-
ror images increases for words relative to objects when TMS was
applied to the L-OTC (see below). Other interactions were all
non-significant (p>0.1).
We the n a s ses s e d the e f f ect s o f s ite, c a tego r y, a n d ori e nta-
tion by restricting the analysis to “same identity” trials. This
analysis revealed significant effects of site (p=0.001) and orien-
tation (p<0.001) but not that of category (F<1). Participants
responded to objects 10 ms faster than to words in L-OTC stim-
ulation, whereas this trend was reversed in R-OTC stimulation
(i.e., ∼7 ms faster to words than to objects), resulting in a signifi-
cant cross-over interaction between site and category (p=0.01).
Response latency to objects was 51ms slower in mirror trials
than in same-orientation trials, whereas this “mirror recognition
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Nakamura et al. Mirror-image discrimination in the left occipitotemporal cortex
cost” (Pegado et al., 2014)wasevengreaterforwords(68ms).
Indeed, the effect of category on mirror recognition cost was
marginally significant (p=0.06). More importantly, there was a
significant triple interaction between site, category and orienta-
tion (p=0.01), suggesting that the between-category difference
in mirror recognition cost was enhanced by the disruption of the
L-OTC relative to that of the R-OTC.
EFFECTS OF TMS ON THE VERTEX
We then performed a third session with 240 trials in which TMS
was delivered to a distant control region (Vx). The behavioral
paradigm and TMS procedure were the same as those in the
main experiment. This control experiment is required because
magnetic stimulation of the R-OTC might change the activation
level of the L-OTC via callosal connections between the left and
right hemispheres. That is, neuropsychological and neuroimag-
ing data show that these homotopic regions may exert a mutually
inhibitory influence on each other (Forss et al., 1999; Fink et al.,
2000; Ueki et al., 2006; Koch et al., 2008; Nakamura et al., 2012b).
Again, participants made few errors during the same-different
judgment task [mean error rate (SD)=4.52 (4.92)%]. Reaction
time data for correct responses are presented in Figure 3.Since
our main interest was to compare the behavioral effects of Vx
stimulation with those of L-OTC and R-OTC, we ran a 2 ×2×
2×2ANOVAseparatelyforeachoftheleftandrightOTC,treat-
ing site (OTC vs. vertex), category (words vs. objects), orientation
(same vs. mirror-reversed), and identity (same vs. different) as
within-participant factors. Therefore the critical comparison here
is the main effect of site and its interaction with other factors.
First, the R-OTC vs. Vx comparison revealed that the main
effect of site never approached significance (422 vs. 420ms,
p>0.5). Moreover, this effect did not interact with any other
factors (p>0.2forallinteractions).Thus,thesefindingssug-
gest that the behavioral effects induced by Vx stimulation did not
differ significantly from those induced by R-OTC stimulation.
Next, the L-OTC vs. Vx comparison revealed that overall
latency was slower in L-OTC stimulation (442 ms) than in Vx
FIGURE 3 | Behavioral results in two control experiments. When TMS
was applied to a cont rol site (Vx) distant from occipitotemporal regions,
participants showed the similar amount of mirror recognition cost between
words and objects. This pattern of behavioral cost during mirror image
processing was also observed when no TMS was applied during the same
behavioral task. Thus, the effects of category, orientation, and identity
overall pr oduced the similar patterns of impact on reaction times between
the two experiments (see Results).
stimulation (420 ms), although this ∼22 ms difference did not
reach significance (p=0.20). The effect of identity was signifi-
cant (p=0.003) and produced a trend of interaction with the
effect of site (p=0.1). The effect of site interacted neither with
that of orientation nor with that of category (p>0.2forboth).
These four factors (site, category, orientation, and identity) pro-
duced no significant triple interactions (p>0.2forall).Lastly,
however, there was a significant quadruple interaction (p=0.01),
similarly to the comparison between L-OTC and R-OTC in the
main experiment (see above). Thus, these results additionally
support the previous finding that L-OTC stimulation produces
a regional specific impact on the mirror recognition process.
COMPARISONS WITH A NON-TMS BASELINE
We fur t her co n d uct e d a b ehav i ora l e x per i ment w i tho u t T MS w i t h
aseparategroupof18participantstodeterminethebaseline
pattern of mirror-image recognition during the same-different
judgment task. These participants also made few errors during
the same-different judgment task [mean error rate (SD)=2.69
(1.88)%]. On the other hand, overall responses were >50 ms
slower in this non-TMS experiment compared to the TMS exper-
iment (see Figure 3). Probably, this large between-group dif-
ference should be attributed to some non-specific behavioral
facilitation effects of TMS, known as “inter-sensory facilitation”
(e.g., Terao et al., 1997). We therefore transformed reaction time
data into a logarithmic scale to compare the mirror recognition
cost between different sessions. The behavioral index for mirror
recognition cost (Figure 4) was obtained by selecting only same-
identity trials and then calculating log RT differences between
same orientation trials and mirror trials for each category for each
session.
FIGURE 4 | Across-session comparisons for mirror recognition cost. For
each session, the magnitude of mirror recognition cost was calculated by
subtracting log-transformed reaction times for mirror trials from those for
same-orientation trials. Magnetic stimulation of the L-OTC produced a large
impact on mirror-image recognition for words but not objects, whereas all
other sessions showed the similar pattern of behavioral effects without
significant between-category differences (see Results).
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Nakamura et al. Mirror-image discrimination in the left occipitotemporal cortex
For this mirror recognition cost, we then examined the effect
of TMS and its interactions with other factors by contrasting each
of the three TMS sites with the non-TMS control. First, the L-
OTC vs. non-TMS comparison revealed no significant effect of
TMS on mirror recognition cost (F<1). However, there was a
marginally significant effect of category (p=0.05), suggesting
that the magnitude of mirror-recognition cost was greater for
words than for objects. Importantly, there was a significant inter-
action between TMS and category (p=0.03), suggesting that
the category-specific impact on recognition cost was greater for
L-OTC relative to the non-TMS. On the other hand, both the R-
OTC vs. non-TMS and the Vx vs. non-TMS comparisons revealed
that the effects of TMS and category and their interaction were all
non-significant (p>0.5forall).Thesefindingssuggestthatthe
overall pattern of mirror recognition cost did not differ between
R-OTC, Vx, and non-TMS sessions.
DISCUSSION
Recent brain imaging studies suggest that fluent reading rests on
adistributedbilateralnetworkextendingfromthelateralfrontal
region to ventral and dorsal visual areas (Dehaene et al., 2005;
Cohen et al., 2008; Nakamura et al., 2012a). Since written lan-
guage is a recent cultural invention dating back only ∼5000 years,
this extensive reading network should be shaped by imposing
learning-related plastic changes upon evolutionarily older neu-
ral systems as a function of cognitive processing demands of
reading (see e.g., Szwed et al., 2014). In particular, mirror-image
discrimination is likely to rely on such experience-dependent pro-
cess occurring in the higher-order visual system during literacy
development. That is, whereas the human ventral visual area
involved in object recognition is generally known to represent
visual objects and their mirror reversals as being the same (Eger
et al., 2004; Vuilleumier et al., 2005; Dehaene et al., 2010b), the
intrinsic propensity for mirror-image generalization should be
partially suppressed through literacy training, since many writ-
ing systems include minimal pairs of mirror-image letters, such
as “b” vs. “d” and “p” vs.”q” (Dehaene et al., 2005). Literacy
development is indeed likely to involve such unlearning pro-
cess, because visual sensitivity to left-right orientation has been
shown to increase with literacy acquisition (Kolinsky et al., 2011;
Dunabeitia et al., 2013). At the neural level, the mirror-image dis-
crimination during reading has been associated with a subpart of
the L-OTC termed the VWFA (Dehaene et al., 2010a,b; Pegado
et al., 2011).
In the present study, we examined whether or not the VWFA
system previously associated with mirror-image discrimination
comprises a local inhibitory mechanism for suppressing neu-
ral activations induced by mirror-reversed letter-strings. We
observed that magnetic stimulation of the L-OTC interfered with
mirror-image recognition more greatly for words than for other
objects. In contrast, the transient disruption of the R-OTC did not
produce such category-specific impact on mirror-image process-
ing. Rather, additional analyses of control experiments showed
that the main effects of category and orientation during R-OTC
stimulation did not differ in effect-size from those obtained from
the Vx and no-TMS sessions, suggesting that TMS of the R-OTC
did not interfere with mirror-image recognition. These findings
therefore suggest that the observed increase in mirror processing
cost for words is a regional specific effect of L-OTC stimulation,
which is distinct from the effects observed for other control sites,
including R-OTC and Vx.
The present results further suggest that the L-OTC in itself
does not exert inhibitory influence over mirror-image represen-
tations of letter-strings, because the visual processing of mirror
words should be facilitated when such local inhibitory circuit is
disrupted by the magnetic stimulation of the L-OTC. Rather, our
results revealed that TMS of this region produced a significant
delay in mirror-image recognition only for words and not for
objects. Since the same-different judgment of visual stimuli and
their mirror reversals relies on their shared, orientation-invariant
representations, this finding concurs with the notion that the
same part of the ventral visual system stores such higher-order,
invariant identity of letter-strings (Dehaene et al., 2005). It is
therefore likely that mirror-image discrimination during skilled
reading does not occur inside the VWFA but rather involve other
orientation-sensitive cortical regions, such as LOC (Eger et al.,
2004; Vuilleumier et al., 2005)andPPC(Poldrack and Gabrieli,
2001).
Indeed, the left and right LOCs are thought to constitute a
“posterior letter recognition system” involved in the visual anal-
ysis of letter shapes (Tarkiainen et al., 2002; Ellis et al., 2009).
It seems rather plausible that literacy training develops a feed-
forward mechanism favoring normally oriented words over their
mirror images, since visual face recognition, i.e., another well-
known example of expert visual recognition, is thought to rely on
a strong structural and functional coupling between these extras-
triate regions and OTCs that is at least partially enhanced by visual
experience (Fairhall and Ishai, 2007; Gschwind et al., 2012). If this
is the case, mirror-image discrimination may be achieved in the
VWFA by collecting strong bottom-up activations of orientation-
sensitive LOC neurons produced by normally oriented letters
and filtering out weaker activations produced by mirror-reversed
letters. Indeed, recent neurobiological data show that stimulus
selectivity, at least for early visual cortex, is mediated by such
feed-forward mechanism incorporating non-linear properties of
cortical neurons (e.g., spike threshold, contrast saturation), rather
than by classical lateral inhibition circuits (Priebe and Ferster,
2008). Thus, if the higher-order ventral visual area also relies on
the similar feed-forward connections, the strong selectivity of the
VWFA to normal oriented letters/words as observed in previous
fMRI studies (Dehaene et al., 2010a; Pegado et al., 2011)may
arise from a bottom-up activation of abstract orthographic codes
driven by excitatory signals from the earlier, orientation-sensitive
LOC regions.
On the other hand, mirror-image discrimination for letters
may also partially rely on the dorsal visual pathway, includ-
ing the PPC, which is generally known to be sensitive to the
orientation of visual stimuli (Culham and Valyear, 2006)and
modulate the activation level of the object-sensitive extrastriate
areas in the control of spatial attention (Serences et al., 2004;
Shomstein and Behrmann, 2006). Recent brain imaging data
indeed suggest that the left and right PPCs participate in a tightly
interconnected network for reading across different writing sys-
tems (Cohen et al., 2008; Nakamura et al., 2012a). Importantly,
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Nakamura et al. Mirror-image discrimination in the left occipitotemporal cortex
however, neuropsychological data suggest that damage to the
PPC causes left-right disorientation for non-linguistic objects
but not for letters (Davidoff and Warrington, 2001; Priftis et al.,
2003; Vinckier et al., 2006). It is therefore possible that efficient
mirror-image discrimination during reading is mediated by the
ventral visual area independently of the parieto-occipital region
(see Pegado et al., 2011 for further discussion). Even if this is the
case, however, it is still open whether and to what extent mirror-
image discrimination of letters can occur automatically without
focused attention. Rather, it might rely on top-down allocation
of spatial attention, since, for instance, mirror-image letters (e.g.,
“b” and “d”) are more easily confused in peripheral vision than
in central vision (Chung, 2010). Moreover, even mirror-image
generalization, i.e., a more innate and intrinsic property of the
ventral visual system and probably less attention-dependent pro-
cess, seems to depend on spatial attention and does not occur
automatically for unattended or unconsciously perceived visual
stimuli (Bar and Biederman, 1998; Eger et al., 2004). Clearly,
further behavioral and brain imaging data should be collected
to determine the relative contribution of the dorsal attention-
control system in mirror-image discrimination during expert
visual word recognition.
To summarize, we found that mirror processing cost increased
for written words and not for other objects when TMS was
applied to the L-OTC. This finding suggests that this region per
se does not comprise a local inhibitory circuit for suppressing
mirror-image representations of letter-strings and better fits with
ahierarchicalmodelwherebytheVWFArepresentsabstractiden-
tity of letter-strings by collecting feed-forward signals from earlier
orientation-sensitive extrastriate regions (Dehaene et al., 2005).
In addition, at the methodological side, an important advantage
of TMS over other brain imaging techniques (e.g., fMRI, mag-
netoencephalography) is that it allows causal inferences about
brain structure and function (Pascual-Leone et al., 1999). The
present results hence provide new causal evidence showing that
the L-OTC is specifically involved in mirror-image discrimina-
tion during fluent reading. Such visual expertise for letters would
rely on a fine tuning of the ventral visual system through liter-
acy development and thus represent a detectable behavioral-level
signature of the literate brain.
ACKNOWLEDGMENT
This work was supported by the Takeda Science Foundation.
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002409
Conflict of Interest Statement: The authors declare that the research was con-
ducted in the absence of any commercial or financial relationships that could be
construed as a potential conflict of interest.
Received: 18 January 2014; paper pending published: 10 March 2014; accepted: 02
May 2014; published online: 21 May 2014.
Citation: Nakamura K, Makuuchi M and Nakajima Y (2014) Mirror-image discrim-
ination in the literate brain: a causal role for the left occpitotemporal cortex. Front.
Psychol. 5:478. doi: 10.3389/fpsyg.2014.00478
This article was submitted to Developmental Psychology, a section of the journal
Frontiers in Psychology.
Copyright © 2014 Nakamura, Makuuchi and Nakajima. This is an open-access arti-
cle distributed under the terms of the Creative Commons Attribution License (CC BY).
The use, distribution or reproduction in other forums is permitted, provided the
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www.frontiersin.org May 2014 | Volume 5 | Article 478 |
64
OPINION ARTICLE
published: 10 July 2014
doi: 10.3389/fpsyg.2014.00703
How does literacy break mirror invariance in the visual
system?
Felipe Pegado 1*, Kimihiro Nakamura
2and Thomas Hannagan3
1Laboratory of Biological Psychology, Department of Psychology and Educational Sciences, KU Leuven University, Leuven, Belgium
2Human Brain Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan
3Laboratoire de Psychologie Cognitive, Fédération de Recherche 3C, Centre National de la Recherche Scientifique, Aix-Marseille University, Marseille, France
*Correspondence: felipepegado@yahoo.com
Edited by:
Tân i a F er n a n d e s, Un i v e rsi t y o f Por t o , Po r t uga l
Reviewed by:
Thomas Lachmann, U niversity of Ka isers lautern, Germany
Keywords: multisensory, multi-system, reading, writing, literacy, alphabetization, mirror invariance, mirror discrimination
Agrowingliteraturehasbeenshowinga
profound impact of alphabetization at sev-
eral levels of the visual system, including
the primary visual cortex (Szwed et al.,
2014)andhigher-orderventralanddor-
sal visual areas (Carreiras et al., 2009;
Dehaene et al., 2010). Importantly, in typ-
ical alphabetization courses, learning to
read is not isolated but instead combined
with both learning to write and learning
to segment the spoken language, relating
all these different representations to each
other. Indeed, learning to write and to pro-
nounce the elementary sounds of language
promotes additional mapping between
the visual and motor systems by linking
visual representations of letters and motor
plans for handwriting and speech produc-
tion. Thus, besides the already recognized
influence of the phonological system, the
potential influence from other neural sys-
tems in the functioning of the visual sys-
tem seems to be relatively neglected. In
this opinion paper we highlight the impor-
tance of multi-systems interplay during
literacy acquisition, focusing on the ques-
tion of how literacy breaks mirror invari-
ance in the visual system. Specifically, we
argue for a large contribution of top-
down inputs from phonological, hand-
writing and articulatory representations
toward the ventral visual cortex during the
development of the visual word form sys-
tem, which then plays a pivotal role in
mirror discrimination of letters in literate
individuals.
HOW PHONOLOGY AFFECTS VISUAL
REPRESENTATIONS FOR READING
A key aspect of alphabetization is to
set in place the audio-visual mapping
known as “phoneme-grapheme corre-
spondence,” whereby elementary sounds
of language (i.e., phonemes) are linked
to visual representations of them (i.e.,
graphemes) (Frith, 1986). This corre-
spondence is progressively acquired and
becomes automatized typically after 3–4
years of training (Nicolson et al., 2001;
Van Atteveldt et al., 2004; Lachmann
and van Leeuwen, 2008; Dehaene et al.,
2010; Lachmann et al., in this special
issue). Illiterates, who do not learn this
audio-visual correspondence, are unable
to show “phonological awareness” (i.e.,
the ability to consciously manipulate
language sounds) at the phonemic level
(Morais et al., 1979; Morais and Kolinsky,
1994), presenting different visual analyti-
cal characteristics (Lachmann et al., 2012;
Fernandes et al., 2014). Accordingly, acti-
vations in phonological areas increases in
proportion to the literacy level of partic-
ipants, e.g., planum temporale responses
to auditory sentences and left superior
temporal sulcus responses to visual pre-
sentations of written sentences (Dehaene
et al., 2010). These results therefore sug-
gest an important link between the visual
and auditory systems created by literacy
training. Indeed, the reciprocal inter-
regional coupling between visual and
auditory cortical areas may constitute
acrucialcomponentforfluentread-
ing, since dyslexic children, who present
slow reading, show reduced activations to
speech sounds in the perisylvian language
areas and ventral visual cortex includ-
ing the Visual Word Form Area (VWFA)
(Monzalvo et al., 2012).
HOW WRITING AFFECTS VISUAL
REPRESENTATIONS FOR READING
In parallel, children (and adults) under
alphabetization also learn to draw letters
of the alphabet. Indeed, writing requires
fine motor coordination of hand ges-
tures, a process guided by online feedback
from somatosensory and visual systems
(Margolin, 1984). In particular, gestures
of handwriting are thought to be repre-
sented in the dorsal part of the premo-
tor cortex, rostral to the primary motor
cortex responsible for hand movements,
i.e., a region first coarsely described by
Exner as the “graphic motor image cen-
ter” (see Roux et al., 2010 for a review).
Exner’s area is known to be activated
when participants write letters but not
when they copy pseudoletters (Longcamp
et al., 2003). Moreover, direct brain stim-
ulation of the same region produces a
specific inability to write (Roux et al.,
2009). Importantly, this region is acti-
vated simply by visual presentations of
handwritten stimuli (Longcamp et al.,
2003, 2008), even when they are presented
unconsciously (Nakamura et al., 2012).
Additionally these activations take place
www.frontiersin.org July 2014 | Volume 5 | Article 703 |
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Pegado et al. Mirror discrimination learning during literacy
in the premotor cortex contra-lateral to
the dominant hand for writing (Longcamp
et al., 2005). These results suggest that
literacy training establishes a tight func-
tional link between the visual and motor
systems for reading and writing. In fact,
it has been proposed that reading and
writing rely on distributed and overlap-
ping brain regions, each showing slightly
different levels of activation depending
on the nature of orthography (Nakamura
et al., 2012). As for the reciprocal link
between the visual and motor components
of this reading network, brain-damaged
patients and fMRI data from normal sub-
jects consistently suggest that top-down
activation of the posterior inferior tempo-
ral region constitutes a key component for
both handwriting (Nakamura et al., 2002;
Rapcsak and Beeson, 2004)andreading
(Bitan et al., 2005; Nakamura et al., 2007).
HOW SPEECH PRODUCTION AFFECTS
VISUAL REPRESENTATIONS FOR
READING
While the impact of auditory phonolog-
ical inputs for literacy acquisition has
been well demonstrated (e.g., phono-
logical awareness studies), relatively less
explored has been the connection between
the speech production system and other
systems during alphabetization. Indeed,
although all alphabetizing children already
speak fluently, an unusual segmenta-
tion and refinement of motor plans for
speech production should be learned
to pronounce isolated phonemes, allow-
ing a multisensory association (explicitly
or implicitly) of these new fine-grained
phonatory representations with visual and
auditory representations. One study has
shown activation in a cortical region
involved in speech production (Broca’s
area) in relation to handwriting learn-
ing and letter identification (Longcamp
et al., 2008). In fluent readers, the inferior
frontal area involved in speech production
in one hand and the VWFA in another
hand show fast and strong inter-regional
coupling (Bitan et al., 2005), which oper-
ates even for unconsciously perceived
words (Nakamura et al., 2007). This dis-
tant visual and articulatory link mediat-
ing print-to-sound mapping is probably
established during the earliest phase of
reading acquisition and serves as a cru-
cial foundation for the development of a
dedicated reading network (Brem et al.,
2010).
LITERACY ACQUISITION AS A
MULTI-SYSTEM LEARNING PROCESS:
THE EXAMPLE OF MIRROR
DISCRIMINATION LEARNING
Taken t o g eth e r, t h ese st u die s c o nv e rge
to the idea that far fromiinfar from a
unimodal training on visual recognition,
literacy acquisition is an irreducibly multi-
system learning process. This lead us to
predict that as one becomes literate, the
expertise acquired through a given modal-
ity is not restricted to it, but can have an
impact on other neural systems.
Perhaps the most spectacular case in
point, and the one we choose to focus
on in this article, is the spontaneous link
between the motor and visual systems
during literacy acquisition. This link is
revealed in the beginning of the alpha-
betization process by the classic emer-
gence of spontaneous mirror writing, i.e.,
writing letters in both orientations indis-
tinctly (Cornell, 1985). Indeed our pri-
mate visual system presents a mirror
invariant representation of visual stimuli,
which enables us to immediately recognize
one image independently of left or right
viewpoints (Rollenhagen and Olson, 2000;
Vuill e u m i e r e t a l . , 2 0 0 5 ; B i e d er m a n a nd
Cooper, 2009). This generates a special dif-
ficulty to distinguish the left-right orienta-
tion of letters (e.g., b vs. d) (Orton, 1937;
Corballis and Beale, 1976; Lachmann,
2002; Lachmann et al. in this special issue).
One account for the emergence of mir-
ror writing is that writing gestures can be
“incorrectly” guided by mirror invariant
visual representations of letters, a frame-
work referred to as “perceptual confusion”
(see Schott, 2007 for a review on this
topic).
In complement, recent studies demon-
strate that after literacy acquisition,
mirror invariance is lost for letter strings
(Kolinsky et al., 2011; Pegado et al., 2011,
2014)andthattheVWFAshowsmirror
discrimination for letters (Pegado et al.,
2011); see figure upper part. Interestingly,
in this special issue, Nakamura and col-
leagues provide evidence for the causal
role of the left occipito-temporal cor-
tex (encompassing the VWFA) in mirror
discrimination by using transcranial mag-
netic stimulation. However, it is still
an open question whether this region
becomes completely independent to
discriminate the correct orientation of
letters or if it still depends on inputs
from phonological, gestural, and/or vocal
representations.
A MULTI-SYSTEM MODEL OF MIRROR
DISCRIMINATION LEARNING
How is mirror discrimination acquired
during the process of literacy acquisi-
tion? Here we sketch a model that takes
into account not only the multisensory
nature of alphabetization but also the
multi-systems interplay, i.e., how repre-
sentations in one system could influence
the functioning of another system (e.g.,
mirror invariance in the visual system).
In Figure 1, we present the hypothetical
“multi-system input model” for mirror-
letters discrimination learning during lit-
eracy acquisition. In order to correctly
and rapidly identify letters for a flu-
ent reading, the VWFA (in red) should
visually distinguish between mirror rep-
resentations of letters (see figure upper
part). Top-down inputs from phonolog-
ical, handwriting and speech production
representations can provide discriminative
information to the VWFA, helping this
area that presents intrinsic mirror invari-
ance, to accomplish its task of letter iden-
tification. This process probably requires
focused attention (not represented in the
figure) during the learning process and
is likely to become progressively automa-
tized. These top-down inputs toward the
VWFA possibly influence this region to
select relevant bottom-up inputs from
lower-level visual areas (represented in
pink in the figure) carrying information
about the orientation of stimuli. For sim-
plicity inter-hemispheric interactions are
not represented here, but it should be
acknowledged that during this learning
process, local computations in the VWFA
can include inhibition of mirror-inversed
inputs from the other hemisphere.
Note that although we illustrate it by
using mirror-letters (b-d or p-q), our
model can eventually be extended to non-
mirror letters, such as “e” or “r” for
instance, given that each letter has a spe-
cific representation at the phonological,
gestural (handwriting) and phonatory sys-
tem. It cannot be excluded however that
for these non-mirror letters, the simple
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Pegado et al. Mirror discrimination learning during literacy
FIGURE 1 | Brain pathways for mirror discrimination learning during
literacy acquisition. Upper: The Visual Word Form Area [VWFA] (in
red) presents mirror invariance before alphabetization and mirror
discrimination for letters after alphabetization. Lower: During
alphabetization, the VWFA can receive top-down inputs with
discriminative information from phonological, gestural (handwriting) and
speech production areas and bottom-up inputs from lower level visual
areas. All these inputs can help the VWFA to discriminate between
mirror representations, thus correctly identifying letters to enable a
fluent reading.
extensive visual exposure to their fixed
orientation could, in principle, be suffi-
cient to induce visual orientation learning
for them. In contrast, this simple pas-
sive learning mechanism is unlikely to
explain orientation learning for mirror let-
ters given that both mirror representations
are regularly present (e.g., b and d).
Thus at least for mirror letters, the dis-
crimination mechanism is more likely to
involve cross-modal inputs, as represented
in our figure. Accordingly, it is known
that learning a new set of letters by
handwriting produces a better discrimi-
nation of its mirror images than when
learning by typewriting (Longcamp et al.,
2006, 2008). Moreover, despite low per-
formances in pure perceptual visual tasks
in mirror discrimination, illiterates are as
sensitive as literates in mirror discrimina-
tion on vision-for-action tasks (Fernandes
and Kolinsky, 2013). Thus, inputs of ges-
tural representations of letters influencing
the VWFA perception could have a special
weight in the processes of learning mirror
discrimination.
It can also be expected that the
existence of mirror letters forces the
visual system to discriminate them,
because it is necessary to correctly read
words comprising mirror letters, such
as in “bad” (vs. “dad”) for instance.
Moreover, evidence suggest that such
mirror discrimination sensitivity in lit-
erates can be partially generalized to
other visual stimuli such as false-fonts
(Pegado et al., 2014) and geometric figures
(Kolinsky et al., 2011). Thus, it is plausible
that during literacy acquisition mirror
letters could “drive” the learning pro-
cess of letter orientation discrimination,
eventually extending it for non-mirror
letters. Accordingly, in writing systems
that do not have mirror letters in their
alphabet (e.g., tamil script), even after
learning to read and write, literates still
present difficulties in mirror discrimi-
nation (Danziger and Pederson, 1998).
In addition, a superior mirror priming
effect for inverted non-mirror letters
(e.g., “r”) relative to mirror letters (e.g.,
“b”) has been reported (Perea et al.,
2011), suggesting thus a more intensive
automatic discrimination for mirror-
letters in comparison to non-mirror
letters.
Although it is not known how mir-
ror discriminations of letters and words
could be achieved in the complete absence
of feedback from phonological, gestural
or speech representations, recent empiri-
cal and computational modeling work on
baboons, who can be trained to acquire
orthographic representations in a purely
visual manner (Grainger et al., 2012;
Hannagan et al., 2014)pavesthewayto
answer this question.
Acknowledging this multi-system inter-
play during literacy acquisition can have
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Pegado et al. Mirror discrimination learning during literacy
potential implications for educational
methods. Interestingly, experiments have
suggested that multisensory reinforce-
ment can present an advantage for literacy
acquisition: arbitrary print-sound corre-
spondences could be facilitated by adding
an haptic component (tactile recogni-
tion of letters) during the learning process
(Fredembach et al., 2009; Bara and Gentaz,
2011). Large scale studies are now needed
to test if promoting multi-system learning
is able to provide a clear advantage in real
life alphabetization.
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Conflict of Interest Statement: The authors declare
that the research was conducted in the absence of any
commercial or financial relationships that could be
construed as a potential conflict of interest.
Received: 08 May 2014; accepted: 18 June 2014;
published online: 10 July 2014.
Citation: Pegado F, Nakamura K and Hannagan T
(2014) How does literacy break mirror invariance in the
visual system? Front. Psychol. 5:703. doi: 10.3389/fpsyg.
2014.00703
This article was submitted to Developmental Psychology,
a section of the journal Frontiers in Psychology.
Copyright © 2014 Pegado, Nakamura and Hannagan.
This is an open-access article distributed under the terms
of the Creative Commons Attribution License (CC BY).
The use, distribution or reproduction in other forums
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www.frontiersin.org July 2014 | Volume 5 | Article 703 |
69
OPINION ARTICLE
published: 23 July 2014
doi: 10.3389/fpsyg.2014.00787
Let’s face it: reading acquisition, face and word processing
Pau lo Ventu ra *
Facult y of Psychology, University of Li sbon, L isboa, Portugal
*Correspondence: paulo.ventura@gmail.com
Edited by:
Tân i a F er n a n d e s, Un i v e rsi t y o f Por t o , Po r t uga l
Reviewed by:
Cees Van Leeuwen, Katholieke Universiteit Leuven, Belgium
Keywords: reading acquisition, neuronal recycling, faces, words, holistic processes
A TIGHT LINK BETWEEN READING
ACQUISITION AND CHANGES IN FACE
PROCESSING
The invention of writing is one of the most
important cultural changes of mankind.
Notably, because reading was invented
only 5000 years ago, there was not suffi-
cient time to evolve a brain system devoted
to visual word recognition. Nevertheless,
learning to read leads to the development
of a strong response to written materials
in the left fusiform gyrus, in the “visual
word form area” (VWFA, e.g., Dehaene,
2009). Consequently, reading must rely on
pre-existing neural systems for vision and
language, which may be partially “recy-
cled” for the specific problems posed by
reading (Dehaene, 2005; Dehaene and
Cohen, 2007). This consistent localization
is related to prior properties of the corre-
sponding tissue, which make it particularly
suitable to the specific problems posed by
the invariant visual recognition of writ-
ten words (Dehaene, 2009): bias for foveal
stimuli (Hasson et al., 2002), posterior-to-
anterior increase in perceptual invariance
(Grill-Spector et al., 1998; Lerner et al.,
2001), and more direct projection fibers
to language areas (Cohen et al., 2000;
Epelbaum et al., 2008).
The neuronal recycling model predicts
that, as cortical territories dedicated to
evolutionarily older functions are invaded
by novel cultural objects, their prior orga-
nization should slightly shift away from
the original function (though the origi-
nal function is never entirely erased). As
a result, reading acquisition should dis-
place whichever evolutionary older func-
tion is implemented in the site of the
VWFA. In a recent fMRI study (Dehaene
et al., 2010)comparingilliteratetoliter-
ate adults, we showed that learning to read
competes with the cortical representation
of other visual objects, especially faces.
With increasing literacy, cortical responses
to faces decrease slightly in the left
fusiform region, while increasing strongly
in the right fusiform area (FFA). Thus,
right-hemispheric lateralization for faces is
increased in literates compared to illiter-
ates. Consistent evidence was also reported
when comparing 9-year-old normal read-
ers and dyslexic children. Not only did
responses to written words showed a
greater left lateralization in normal read-
ers, but responses to faces were also more
strongly right lateralized (Monzalvo et al.,
2012;cf.alsoMonzalvo, 2011).
Further developmental studies also
reveal a tight link between reading acqui-
sition and changes in face processing.
Cantlon et al. (2011) demonstrated that
4-year-old-children show decreasing
responses to faces in the left fusiform
gyrus with increasing knowledge of let-
ter and number symbols. Li et al. (2013)
found for Chinese preschooler’s a facili-
tative effect of early exposure to reading
in neural responses to visual words. Such
a facilitative effect had a temporary cost
in neural response to faces, which did not
show the mature pattern seen in adults.
Dundas et al. (2012) studied the devel-
opment of hemispheric specialization for
written words and faces in children, ado-
lescents and adults, and found that the
left-hemispheric specialization for words
develops prior to the right-hemispheric
specialization for faces, with face lateral-
ization related to reading comprehension
ability (cf. also Pinel et al., 2014).
The competition between different cat-
egories seems to rely on enhanced neu-
ronal specificity, namely on decreased
responses to non-preferred stimuli as
opposed to an increased response to the
preferred category. Indeed, Cantlon et al.
(2011) found a decrease for non-preferred
stimuli in VWFA and FFA during child
development. Joseph et al. (2011) reported
both progressive changes,i.e.,increasing
face-specialization in a brain region with
age, and regressive changes, i.e., decreas-
ing face-specialization with age. Indeed,
many brain regions recruited in children
for face processing showed reduced spe-
cialization for faces by adulthood. Such
regressive changes support the idea that
some areas of the face network may lose
out, at a cellular and a functional level,
to promote specialization. Consistent with
this scenario, in Pinel et al. (2014)’s
study stronger leftward asymmetry for the
VWFA and rightward asymmetry for the
FFA were characterized by reduced activa-
tion in homolog areas of the contralateral
hemisphere.
All these observations support the
existence of competition for cortical
space between the VWFA and the pre-
existing neural coding of faces (Dehaene,
2005; Dehaene and Cohen, 2007; Plaut
and Behrmann, 2011), with some dis-
placement of fusiform face-sensitive
areas toward the right hemisphere. A
similar theoretical perspective (Nestor
et al., 2012; Behrmann and Plaut,
2013) espouses a competitive interac-
tion between distributed circuits for faces
and word recognition for foveally-biased
cortex, constrained by the need to inte-
grate reading with the language system
primarily left-lateralized.
Recently, we investigated the behav-
ioral consequences of this brain reorga-
nization (Ventura et al., 2013). Using the
face composite task, we found that literates
are consistently less holistic than illiterate
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Ven tu ra Reading, face and word processing
individuals without any reading experi-
ence. The effect is not even specific to faces,
but extends to houses. It thus seems that
literacy induces a shift in the ability to
deploy analytic visual strategies, over and
above any specific effect that it may have
on face processing, at least in tasks requir-
ing selective attention to part of an object:
it reduces automatic reliance on holistic
processing when it is detrimental to the
task by enabling the use of a more analytic
and flexible processing strategy (Vent u r a
et al., 2013). These findings are in appar-
ent contradiction with Lachmann et al’s
(2012) study of congruence effects for let-
ters vs. geometric shapes. Illiterates dis-
played negative CEs for both letters and
shapes a finding which was interpreted as
indicative of a generic and primary ana-
lytic perceptual processing strategy that is
not reading specific, on par with the holis-
tic strategy. In a previous study (Ven tu r a
et al., 2008) using the Framed-Line-test,
we showed that both illiterates and ex-
illiterates use context dependent/holistic
processing. These apparently contradic-
tory results most probably result from
ahostoffactorsincludingcharacter-
istics of the different stimuli, different
task demands, and different meanings of
analytic and holistic in these different
studies.
In sum, the studies reviewed show
that the acquisition of reading has an
extensive impact on the developing brain
and reveal a tight link between reading
acquisition and changes in face process-
ing. In the following section I evalu-
ate whether reading acquisition leads to
words becoming an object of visual exper-
tise with some processing characteris-
tics similar to faces and other objects of
expertise.
WORDS AS AN OBJECT OF VISUAL
EXPERTISE
Faces are made from common features
(eyes, nose, mouth, etc.) arranged in the
same general configuration. Thus, beyond
the presence of specific features or the
location of these features, subtle differ-
ences in facial features and their spatial
relations are particularly useful for suc-
cessful recognition of a given face (e.g.,
Maurer et al., 2002). To facilitate extrac-
tion of configural information people pro-
cess faces holistically—as a whole—rather
than as a collection of individual face
features.
The many thousands encounters with
visual words lead to a visual expert pro-
cessing of these stimuli. Like in face pro-
cessing, recognition of written words relies
on both their features (e.g., letters) and
the configuration between them. Recent
work by Wong and colleagues adopting
the sequential matching paradigm com-
monly used with faces showed HP to be
a marker of expertise for perception of
English words (Wong et al., 2011). Wong
and colleagues also showed that HP of
words was sensitive to amount of experi-
ence with the stimuli, with larger holistic
processing for native English readers than
Chinese readers who learned English as
their second language. Holistic process-
ing of Chinese characters also seems to
develop as one acquires expertise (Wong
et al., 2012). Indeed, expert Chinese read-
ers displayed a larger holistic processing
for characters than non-characters.
The larger holistic processing of words
with reading experience seems in apparent
contradiction with our evidence of smaller
holistic processing of faces and houses
(Ventura et al., 2013). This discrepancy
may stem from differences in the processes
that lead to the development of holistic
processing in the face/object domain vs.
word domain: fine subordinate-level dis-
crimination among highly similar objects
vs. the development with reading exper-
tise of orthographic representations com-
prising multiple components that can be
processed in parallel (Wong et al., 2012),
enabling direct access to the lexicon. In this
vein, it would be interesting to evaluate
more directly the development of holis-
tic processing of words as children develop
reading proficiency. The beginning reader
uses a letter-by-letter reading strategy. It
is during this relatively slow process of
phonological recoding that exposure to
printed words enables the setting up of a
specialized system for parallel letter pro-
cessing (cf. Share, 1995; Grainger et al.,
2012). One might predict a relationship
between the development of this parallel
orthographic processing and HP of words.
Although the same composite
paradigm has been used to reveal HP
for faces and words, this does not mean
that the same mechanisms underlie the
effects for the two domains (Chen et al.,
2013). However, Chen et al. (2013) showed
that HP of words has an early perceptual
locus similar to that for faces. Nevertheless,
the correlate of HP for characters was P1
(reflecting perceptual processing in extras-
triate visual cortex) different from the
N170 commonly found for face HP.
Reading is undoubtedly an expert
visual function and these experiments
show that word perception can be affected
by holistic processes. However, there are
fundamental distinctions between words
and faces. The mature reading network
comprises not only a visual shape analy-
sis (VWFA system), but also components
involved in print-to-sound translation and
access to word meaning.
Considering print-to-sound transla-
tion, classic studies (e.g., Ziegler et al.,
2000)haveshownthatuponseeinga
written word both an orthographic and
a phonological code are rapidly acti-
vated, although this last code lags slightly
beyond the orthographic code. It is clear
that the experiments of Wong and col-
leagues show HP for words: matching tar-
get parts of a word was interfered by
the irrelevant parts, and such interfer-
ence was reduced when the parts were
misaligned. But this reduction with mis-
alignment might result not (only) from
disruption of visual configural processes,
but (also) from a disruption of the phono-
logical code. This question is the subject
of ongoing research. One avenue is to
compare computer vs. handwritten print.
Letters in handwritten words are noisy,
variable, and ambiguous and their physical
forms are affected by neighboring letters
and thus configural processes may assume
a more prominent role in handwritten
words (Barnhart and Goldinger, 2013).
If the effects found in the word com-
posite task are indeed due to configural
visual processes, HP should be greater for
handwritten words. If, however, the effects
are, at least in part, due to disruption of
phonological codes, there should be small
differences between both types of words.
Another avenue is to use words with letters
that have different pronunciations (e.g.,
“rena,” dear, and “remo,” rowing, in which
the “e” grapheme has different phonolog-
ical values). If the effects reported above
are purely visual, these different pro-
nunciations should not influence the HP
of words.
Frontiers in Psychology |DevelopmentalPsychology July 2014 | Volume 5 | Article 787 |
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Ven tu ra Reading, face and word processing
Another interesting point concerns
the definition of the left and right
parts of the (alphabetic) words used in
the holistic paradigm. Written words
have several linguistic units: syllables,
onsets, and rimes, graphemes, and let-
ters. In the experiments of Wo ng et a l .
(2011),forsomestimulitheleft-right
division respects a division between
two psycholinguistic units—onset and
rime (e.g., cr|ew)—while for others
the division straddles psycholinguis-
tic units: onset and nucleus vs. coda
(e.g., ki|ck). It would be interesting
to compare systematically the holis-
tic/configural effects for sets of words
in which the left|right division respects
adivisionbetweentwopsycholinguis-
tic units vs. a left|right division that do
no respect such a division. If the effects
reported are indeed due to configu-
ral/holistic processes, they should occur
even when the left|right division straddles
psycholinguistic units.
In sum, words are psycholinguistics
units comprising both perceptual and
linguistic factors. The many thousands
encounters with words by the typical liter-
ate person give rise to a perceptual exper-
tise with effects similar to what has been
observed for faces and other objects of
expertise. However, further clarification
of the origin of HP effects for words is
needed.
In conclusion, reading acquisition leads
to changes in face processing and extensive
reading experience can result in expertise
effects for words similar to what has been
found for faces and other objects of face-
like expertise.
ACKNOWLEDGMENTS
I thank Alan Chun-Nang Wong for his
availability and for helpful comments on
apreviousversionofthismanuscript.I
thank the Reviewer for helpful comments
and suggestions.
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Conflict of Interest Statement: The author declares
that the research was conducted in the absence of any
commercial or financial relationships that could be
construed as a potential conflict of interest.
Received: 22 April 2014; accepted: 03 July 2014;
published online: 23 July 2014.
Citation: Ventura P (2014) Let’s face it: reading acqui-
sition, face and word processing. Front. Psychol. 5:787.
doi: 10.3389/fpsyg.2014.00787
This article was submitted to Developmental Psychology,
a section of the journal Frontiers in Psychology.
Copyright © 2014 Ventura. This is an open-access
article distributed under the terms of the Creative
Commons Attribution License (CC BY). The use, dis-
tribution or reproduction in other forums is permit-
ted, provided the original author(s) or licensor are
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demic practice. No use, distribution or reproduc-
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