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Sex Differences in the Human Visual System

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Abstract

This Mini-Review summarizes a wide range of sex differences in the human visual system, with a primary focus on sex differences in visual perception and its neural basis. We highlight sex differences in both basic and high-level visual processing, with evidence from behavioral, neurophysiological, and neuroimaging studies. We argue that sex differences in human visual processing, no matter how small or subtle, support the view that females and males truly see the world differently. We acknowledge some of the controversy regarding sex differences in human vision and propose that such controversy should be interpreted as a source of motivation for continued efforts to assess the validity and reliability of published sex differences and for continued research on sex differences in human vision and the nervous system in general.
Mini-Review
Sex Differences in the Human Visual
System
John E. Vanston and Lars Strother*
Department of Psychology, University of Nevada, Reno, Reno, Nevada
This Mini-Review summarizes a wide range of sex differ-
ences in the human visual system, with a primary focus
on sex differences in visual perception and its neural
basis. We highlight sex differences in both basic and
high-level visual processing, with evidence from behavior-
al, neurophysiological, and neuroimaging studies. We
argue that sex differences in human visual processing, no
matter how small or subtle, support the view that females
and males truly see the world differently. We acknowl-
edge some of the controversy regarding sex differences
in human vision and propose that such controversy
should be interpreted as a source of motivation for con-
tinued efforts to assess the validity and reliability of pub-
lished sex differences and for continued research on sex
differences in human vision and the nervous system in
general. V
C2016 Wiley Periodicals, Inc.
Key words: visual perception; human visual system;
sex-linked disorders; object recognition; cerebral
laterality
In contrast to reproductive capacity, sex differences
in human brain function are largely a matter of degree.
This Mini-Review of sex differences in the human visual
system presents a large body of evidence indicating that
sex differences in visual perception and its neural basis are
real and lends support to the folk belief that males and
females really do see the world differently, even if only to
a degree. Even without reviewing the relevant evidence
in full, an argument can easily be made in favor of this
view. For example, body size is a widely accepted exam-
ple of sexual dimorphism in humans. Therefore, if body
size influences visual perception, then females must see
the world differently from males. In accordance with this,
findings from psychology show that the world we per-
ceive is not equivalent to the physical world but is instead
biased and scaled with respect to the size of one’s body
and relevant body parts (Stefanucci and Geuss, 2009;
Linkenauger et al., 2010, 2014; van der Hoort and
Ehrsson, 2014).
In addition to direct evidence that males and females
see the world differently as a result of body size, sex
differences in the size of the human brain also imply dif-
ferences in visual perception. The brains of male humans
are larger than those of females, even after differences in
body size are taken into account (Breedlove, 1994;
Nopoulos et al., 2000). Thus, if differences in brain size
predict differences in visual perception, then we must
again conclude that females and males see the world dif-
ferently. As it turns out, individuals with larger visual cor-
tices show greater context-independent visual sensitivity
to differences in basic physical properties, such as the size
and orientation of a visual stimulus (Schwarzkopf et al.,
2011; Song et al., 2013). Given that males tend to have a
larger visual cortex than females (Amunts et al., 2007;
Handa and McGivern, 2015), we can reasonably deduce
that males and females see the world differently with
regard to the visual processing of stimulus size and orien-
tation, which has been demonstrated empirically (see,
e.g., Brabyn and McGuinness, 1979; Phillips et al., 2004),
and that this may be related to sex differences in the size
of the visual cortex. In short, sex differences in both body
size and brain size predict sex differences in visual percep-
tion. This Mini-Review summarizes and discusses many
SIGNIFICANCE
The importance of sex differences in human neuroscience, especially
cognitive neuroscience, may be underappreciated. This Mini-Review
summarizes reports of sex differences in visual perception and related
neural substrates. Sex-linked disorders (e.g., autism and schizophrenia)
are associated with abnormal visual function, and there are many
reports of sex differences at various levels of visual processing. There-
fore, understanding the way in which sex and vision interact has
implications for the study of disease processes and our knowledge of
how the visual system works as a whole.
*Correspondence to: Lars Strother, Department of Psychology, Universi-
ty of Nevada, Reno, 1664 N. Virginia St., Mailstop 296, Reno, NV
89557. E-mail: lars@unr.edu
Received 31 March 2016; Revised 20 July 2016; Accepted 1 August
2016
Published online 7 November 2016 in Wiley Online Library
(wileyonlinelibrary.com). DOI: 10.1002/jnr.23895
V
C2016 Wiley Periodicals, Inc.
Journal of Neuroscience Research 95:617–625 (2017)
additional sex differences in visual perception and its
basis in the human visual system and in the visual cortex
in particular. We begin with a comprehensive summary
of sex differences in the visual processing of basic stimu-
lus properties and the prospective neural basis of such
differences. We then review sex differences in object
recognition, some of which are related to sex differences
in cerebral laterality as well as nonvisual influences on
visual cortical processing. We also mention sex differ-
ences in visuospatial processing, a topic that has received
considerably more attention in the literature than most
of the other differences reported here. We keep this sec-
tion very brief because sex differences in visuospatial
processing are not clearly related to sex differences in
visual perception, the latter of which are of primay
interest here.
SEX DIFFERENCES IN BASIC VISUAL
PROCESSING
Individual differences in various visual sensitivities are
ubiquitous. However, because such differences are usually
a matter of degree, they typically go unnoticed except
when measured psychophysically. This section summa-
rizes sex differences observed in standard psychophysical
studies of visual perception and also presents related find-
ings from neurophysiological and neuroimaging studies.
Contrast Sensitivity
The luminance contrast of an image refers to varia-
tions in light intensity at different locations within the
image. Our ability to perceive contrast is a function of
spatial frequency, the periodicity of luminance contrast
(i.e., how many times a stimulus changes from light to
dark per unit space). Any image can be broken down into
light intensity and spatial frequency (ignoring color for
the moment), and this type of image decomposition is a
fundamental basis of visual cortical processing (see, e.g.,
Tootell et al., 1981). There is also compelling evidence
that males and females differ in this fundamental type of
visual processing.
Brabyn and McGuinness (1979) measured contrast
sensitivity by having human observers detect gratings of
different contrasts and spatial frequencies. This standard
psychophysical experiment allowed the authors to com-
pare detection performance between male and female
observers. Briefly, they found that females had higher
sensitivity in the lower spatial frequencies and males had
higher sensitivity in the higher spatial frequencies. These
authors speculated that this sex difference reflects differ-
ences in visual pattern analysis mode in which females
emphasize use of low spatial frequencies that carry
information about overall object form, whereas males
use a more “segregative” mode that emphasizes individ-
ual objects and fine detail inherent in high spatial fre-
quency visual input. Based on their conjecture, this
finding of differences in the contrast sensitivity of males
and females may be related to subsequent reports of sex
differences in local vs. global visual processing (Roalf
et al., 2006), although there are notable differences in
the methods and results for these sorts of tasks (see,
e.g., Kimchi et al., 2009). To the best of our knowl-
edge, Brabyn and McGuinness (1979) have made the
strongest case for sex differences in contrast sensitivity.
However, there is surprisingly little evidence of efforts
to replicate their findings. An exception is a study by
Abramov et al. (2012a) in which measures of contrast
sensitivity and other psychophysical measures were
acquired from a large sample of observers. In contrast
to Brabyn and McGuinness, Abramov and colleagues
found that males had higher contrast sensitivity at all
spatial frequencies, with greater differences at higher
spatial frequencies. That is, despite dissimilarities in the
results (and methods) of the two studies, both showed
compelling evidence of sex differences in contrast sensi-
tivity (see also Foutch and Peck, 2013); additional study
is warranted.
Visual Acuity
Our ability to resolve fine detail is related to but dis-
tinct from contrast sensitivity. The limits of visual acuity
can be measured by having an observer detect a small off-
set between two thin lines or identify the orientation of
increasingly small letters. Visual acuity has consistently
been shown to be better in males (Burg, 1966; McGuin-
ness, 1976; Ishigaki and Miyao, 1994; Abramov et al.,
2012a). Although this finding has also been observed in
other mammals (Seymoure and Juraska, 1997), some have
speculated that sex differences in visual acuity in humans
are related to the roles that men and women played in
early human hunter–gatherer societies, in which males
may have been required to be able to identify prey or
threats at greater distances (Silverman and Eals, 1992;
Sanders et al., 2007; Stancey and Turner, 2010; Abramov
et al., 2012a). On the other hand, females show evidence
of superior visual acuity under different lighting condi-
tions, which may or may not be related to the hunter–
gatherer interpretation. Specifically, McGuinness (1976)
found that, under scotopic conditions (i.e., when there
was very little light), female subjects had higher sensitivity
to contrast.
Color Perception
Sex differences in our ability to perceive color can
be traced genetically to our nonhuman primate ancestors
(Jacobs et al., 1981, 1993, 1996; Jacobs, 1983). The spec-
tral sensitivities of many of the photoreceptors in the reti-
na are determined by genes on the X chromosome (Neitz
and Neitz, 2011). In addition to causing higher rates of
color vision deficiency in males, this creates the possibility
of females expressing multiple types of the same photo-
pigment (Lyon, 1962). It is possible that this is a basis of
sex differences in color sensitivity reported in some stud-
ies (Rodriguez-Carmona et al., 2008; Jordan et al., 2010),
although the evidence for such differences is mixed
(Hood et al., 2006).
618 Vanston and Strother
Journal of Neuroscience Research
In addition to potential differences in spectral sensi-
tivity, there are sex differences in what are considered the
unique (or pure) hues (Kuehni, 2001) as well as in the
naming of monochromatic (one color) lights (Abramov
et al., 2012b). Sex differences have also been shown for
color preference (Eysenck, 1941; Guilford and Smith,
1959; Helson and Lansford, 1970; Sinha et al., 1970; Gel-
ineau, 1981; Hurlbert and Ling, 2007; Sorokowski et al.,
2014), although these findings are complicated by the
interaction of biological, environmental, and cultural fac-
tors (Franklin et al., 2010; Taylor et al., 2013; Hurlbert
and Owen, 2015). Bimler et al. (2004) found that, in
judging color, women tended to place more weight on
variation along a red–green dimension, whereas men
based judgments more on brightness variation. Finally,
sex differences have been shown for a color naming task,
even in the absence of a difference in photoreceptor spec-
tral sensitivities (Murray et al., 2012). This could be due
to differences in visual cortical function in known color
areas in the visual cortex (McKeefry and Zeki, 1997) and
could possibly be related to top-down influences on these
areas (Siok et al., 2009). In short, although sex differences
in color vision may be related to both retinal and cortical
factors, additional studies are required to validate and elu-
cidate such differences.
Motion Perception
Although there is some evidence that motion sensi-
tivity differs between females and males, the few reports
of sex differences were complicated by interactions of sex
with age (Gilmore et al., 1992; Schrauf et al., 1999). Ana-
tomical differences in known motion processing areas of
human visual cortex (i.e., cytoarchitectonically defined
area h0c5) were observed in one study (Amunts et al.,
2007), and a study of biological motion perception (i.e.,
perceived movement of the human body) by Schouten
et al. (2010) showed sex differences (see also Anderson
et al., 2013; Pavlova et al., 2015), which may be related.
Despite the paucity of reported sex differences in motion
perception, this topic deserves additional systematic study,
especially given the centrality of motion perception in
human vision.
Related Findings From Electroencephalography
and Functional Magnetic Resonance Imaging
Visual evoked potentials (VEPs), which contain
characteristic components (peaks and troughs within a
voltage waveform), are routinely used to measure brain
responses to visual stimulation by electroencephalography
(EEG). VEP studies have shown that early components
(e.g., P50, N70, and P100) have higher amplitudes (La
Marche et al., 1986; Celesia et al., 1987; Mitchell et al.,
1987; Shibata et al., 2000; Sharma et al., 2015) and/or
shorter latencies (Stockard et al., 1979; Celesia et al.,
1987; Emmerson-Hanover et al., 1994; Shibata et al.,
2000; Malcolm et al., 2002; Langrova et al., 2012;
Proverbio et al., 2012; Sharma et al., 2015) in females
compared with males (but see Grabowska et al., 1992).
There is evidence that the properties of these VEP com-
ponents are related to contrast sensitivity (discussed earli-
er) performance (Allen et al., 1986; Norcia et al., 1989;
Souza et al., 2007), although the sex differences seen in
these studies may have been secondary to underlying ana-
tomical differences (Christie and McBrearty, 1977; Deka-
ban and Sadowsky, 1978; Reilly et al., 1978; Allison
et al., 1983). Other studies have shown that sex differ-
ences in VEPs are not related to differences in gonadal
hormones (Buchsbaum et al., 1974; Dyer and Swartz-
welder, 1978) and arise in the visual cortex, not in the
retina (Celesia et al., 1987; Tomoda et al., 1991).
In addition to sex differences revealed by EEG,
functional magnetic resonance imaging (fMRI) studies
have shown a variety of vision-related sex differences (for
a review of sex differences in neuroimaging studies see
Sacher et al., 2013). As mentioned above, visual cortical
neurons are widely implicated in contrast sensitivity and
visual acuity, and studies have shown some fMRI evi-
dence of sex differences in blood oxygen level-dependent
(BOLD) signal in the visual cortex (Hedera et al., 1998;
Levin et al., 1998; Cohen and DuBois, 1999; Cowan
et al., 2000), although some of the results of these studies
conflict with one another. The sex differences in color
perception discussed above might also correspond to sex
differences in the visual cortex, which could be measured
with fMRI (McKeefry and Zeki, 1997); however, to the
best of our knowledge, there have been no such reports.
SEX DIFFERENCES IN HIGH-LEVEL VISION
There are two major pathways or streams of cortical proc-
essing in the human visual system, a dorsal stream that
supports visually guided action and a ventral stream that
supports conscious visual perception (Goodale and Mil-
ner, 1992). The two streams diverge in the occipital lobe,
with the dorsal stream proceeding anteriorly from primary
visual cortex (V1) into parietal cortex and the ventral
stream proceeding from V1 to lateral and ventral portions
of occipital and temporal cortex. This section focuses on
sex differences in the ventral stream, especially those
revealed by fMRI.
Object-Selective Lateral Occipital Cortex
Visual object recognition is a defining function of
the ventral visual stream, and there is some, albeit limited,
evidence of sex differences in object recognition for
humans. Previously, this Mini-Review cited a study by
Schwarzkopf et al. (2011) indicating that the size of the
visual cortex influences object perception, in particular,
the perception of object size. Although the Schwarzkopf
et al. study focused on individual differences in the size of
V1, there is considerable evidence that higher tier visual
cortical areas in the ventral stream also play an important
role in the perception of object size and objects more
generally. Among these, the object-selective lateral occip-
ital cortex (LOC) has shown consistently strong fMRI
responses to object vs. nonobject stimuli (Malach et al.,
1995; Grill-Spector et al., 1998; Kourtzi and Kanwisher,
Visual System Sex Differences 619
Journal of Neuroscience Research
2001; Strother et al., 2010). Although we were unable to
find any reports of sex differences directly related to LOC
involvement in the perception of object size, we think
that this possibility warrants additional study given the
involvement of the LOC (in addition to V1) in the per-
ception of object size (Konkle and Oliva, 2012; Konkle
and Caramazza, 2013) and the sex difference in object
size perception reported previously (Phillips et al., 2004).
Additionally, sex differences in object recognition,
including sex differences in the visual recognition of spe-
cific categories of objects (McGugin et al., 2012), may be
due to sex differences in cortical thickness in the ventral
visual cortex (McGugin et al., 2016), including LOC and
also category-selective visual cortical areas, to which we
turn next.
Category-Selective Ventral Temporal Cortex
Within the ventral stream there are category-
selective brain areas composed of neurons that appear to
be tuned to visual properties that apply to specific catego-
ries of objects (Grill-Spector and Malach, 2004). For
instance, faces are represented by neurons in a fusiform
face area (FFA; Kanwisher et al., 1997). Sex differences in
face perception and the neural basis of face processing
have been reported (Platek et al., 2005; Aleman and
Swart, 2008; Proverbio et al., 2010, 2012; Verhallen
et al., 2014; Proverbio and Galli, 2016), and, although the
FFA has not been implicated directly, its involvement is
clearly implied by the results of some studies (e.g., Loven
et al., 2014; Verhallen et al., 2014). Anatomically adjacent
to the FFA, the extrastriate body area (EBA) shows rela-
tively strong BOLD responses to images of bodies com-
pared with faces and other nonbody objects (Downing
et al., 2001). Male observers show stronger threat-related
BOLD responses in the EBA than do females when they
view videos of other males acting in a threatening manner
(Kret et al., 2011), which may be related to behavioral sex
differences in threat perception (Trnka et al., 2007). The
authors of the above-cited studies argue for the impor-
tance of sex differences in social and affective neurosci-
ence, and, by virtue of having shown differences in the
ventral visual stream, one could extend their argument to
visual neuroscience.
Feedback Effects on Visual Cortical Processing
The ventral visual cortex, including early visual
areas, receives feedback from nonvisual areas, including
the prefrontal cortex and various subcortical structures.
One of the most commonly reported vision-related sex
differences concerns feedback to the visual cortex from
the amygdala, especially during the viewing of aversive
visual stimuli. Although the amygdala does not perform
visual processing per se, it nevertheless influences dispa-
rate aspects of visual function, from gaze control to food
perception (Morris and Dolan, 2001), and has numerous
feedback projections to the visual cortex (Amaral et al.,
1992; Freese and Amaral, 2005). Males have larger gray
matter volume in the amygdala than do females (Ruigrok
et al., 2014), and this may be related to some of the many
sex differences reported concerning the role of the amyg-
dala in visual processing. Perhaps most notably, the amyg-
dala plays a central role in the visual processing of facial
expression (Vuilleumier et al., 2001; Adolphs, 2004), and
several studies have shown sex differences in amygdalar
BOLD activity in response to emotional facial stimuli
(Fischer et al., 2004; McClure et al., 2004; Fusar-Poli
et al., 2009; Kempton et al., 2009). Although the patterns
of amygdalar response in these studies vary, one common
finding has been an interaction between sex and the emo-
tional valence of the stimulus. In particular, females tend
to show a stronger neural response to negative emotional
stimuli, whereas men show stronger responses to positive-
ly valenced stimuli (Lang et al., 1998; Klein et al., 2003;
Wrase et al., 2003; McClure et al., 2004; Stevens and
Hamann, 2012). The amygdala has also been shown to
play a role in the processing of sexual stimuli (Hamann
et al., 2004), to which men and women have been shown
to respond differently (for a review of these differences
see Rupp and Wallen, 2008). Various brain imaging stud-
ies have shown sex differences in the pattern of response
to sexual stimuli (e.g., Sabatinelli et al., 2004), in several
cases with neural responses correlating with subjective
arousal (Karama et al., 2002; Costa et al., 2003). Lee et al.
(2015) found that men and women had distinct patterns
of functional connectivity when viewing sexually explicit
visual stimuli, and, in men, the activity in a network con-
necting visual and frontal areas was correlated with plasma
testosterone levels.
CEREBRAL LATERALITY, VISION, AND
LANGUAGE
Cerebral laterality refers to the lack of functional symmetry
between right and left hemispheres with respect to a vari-
ety of perceptual, cognitive, and motor behaviors. Many
studies have shown sex differences in degree of laterality,
which may also relate to neuroanatomical differences
between left and right cortical hemispheres (Gur et al.,
1999). In some cases, the laterality of brain function is
obvious and undisputed (e.g., language and handedness),
but in human vision this is not always the case. In an
exhaustive review of experiments on sex differences in
laterality, Hiscock et al. (1995) concluded that most if not
all findings of vision-related sex differences in laterality
were genuine.
The most commonly reported sex difference in
cerebral laterality is decreased laterality in females com-
pared with males. This type of finding has led to the gen-
eral idea that males’ brains are optimized for within-
hemisphere connectivity, whereas females’ brains are bet-
ter wired for between-hemisphere connectivity (Ingalha-
likar et al., 2014). Although this idea has clear limits, it is
conceivable that males and females exhibit universal dif-
ferences in degree of laterality within the visual system,
and, even if these differences are small, they could be
important. As proposed previously, sex differences in lat-
erality could be related to sex differences in the
620 Vanston and Strother
Journal of Neuroscience Research
development of reading ability (Rutter et al., 2004), espe-
cially given the existence of left-lateralized visual word
recognition mechanisms (McCandliss et al., 2003;
Strother et al., 2016), as well as sex differences in the
functional organization of the brain for language more
generally (Shaywitz et al., 1995, 1998). Given the rela-
tively large number of sex difference findings of laterality
related to face perception (Rizzolatti and Buchtel, 1977;
Jones, 1979; Godard and Fiori, 2010; Proverbio et al.,
2010, 2012; Tiedt et al., 2013) and evidence of a relation-
ship between face perception and word recognition
(Behrmann and Plaut, 2013; Strother et al., 2016), it
would be interesting to explore whether parallel sex dif-
ference effects are observed for visual word recognition.
It would be especially interesting to examine prospective
developmental sex differences in visual field laterality for
visual word recognition (e.g., with the methods of Dun-
das et al., 2013), a direction of research motivated by sex
differences in visual recognition ability observed in non-
human primates (Bachevalier and Hagger, 1991) as well as
reading-related sex differences in cerebral laterality in
humans (Bradshaw et al., 1977; Bradshaw and Gates,
1978; Rossell et al., 2002).
There is a prevalent but contentious type of finding
with regard to sex differences in the size and shape of the
splenium of the corpus callosum. Although some articles
have reported that the splenium has a relatively greater
area and a more bulbous shape in females compared with
males (Wisniewski, 1998) and may be related to sex dif-
ferences in word recognition ability (Walla et al., 2001;
Carreiras et al., 2009), such findings are partially tempered
by conflicting findings from other studies that have
revealed potential confounds (Luders et al., 2014). If the
findings reported by Wisnieski (1998), Walla et al. (2001),
and Carreiras et al. (2009) are valid, however, sex differ-
ences in the size and shape of the splenium could be relat-
ed to sex differences in intrahemispheric vs.
interhemispheric neural processing (Ingalhalikar et al.,
2014). The splenium plays a critical role in the sharing of
hemifield-specific visual information between left and
right hemispheres (Berlucchi, 2014), and splenium dam-
age or removal severely impairs interhemispheric transfer
of visual information (Clarke et al., 2000; Forster and
Corballis, 2000), even when other commissures remain
intact. Related to its involvement in the interhemispheric
transfer of visual information, the splenium plays an inte-
gral role in word recognition and reading (Molko et al.,
2002; Cohen et al., 2003) and could therefore be relevant
to sex differences in the development of reading ability
(Rutter et al., 2004).
VISUOSPATIAL ABILITY
Over the past several decades, many studies have reported
sex differences in visuospatial ability, in particular, superi-
or performance in males ( Maccoby and Jacklin, 1974;
Linn and Petersen, 1985; Voyer et al., 1995). Unfortu-
nately, visuospatial performance has been measured by
extremely diverse stimuli and tasks that differentially
engage human visual and cognitive systems (including the
dorsal visual stream), with fairly disparate tasks showing
varying degrees of sex differences in performance (Miller
and Halpern, 2014). This complicates our understanding
of the basis of visuospatial ability in the visual system and
in the brain in general. For example, males have been
shown to perform better on mental rotation tasks (Mac-
coby and Jacklin, 1974; Sanders et al., 1982; Maeda and
Yoon, 2015), determination of spatial relationships (Wit-
kin et al., 1967; Liben, 1978; Bagust et al., 2013), and
navigation (Astur et al., 1998; Moffat et al., 1998). How-
ever, the cause of these differences in performance, some
of which can be observed in infancy (Quinn and Liben,
2008; Alexander and Wilcox, 2012), is unclear (Reilly
and Neumann, 2013; Miller and Halpern, 2014), and
there is mixed evidence that spatial training can eradicate
sex differences in visuospatial performance (Parames-
waran, 1995; Vasta et al., 1996; Uttal et al., 2013).
Although some of these tasks (e.g., mental rotation) are
sometimes associated with visual processing in the dorsal
stream (Podzebenko et al., 2002), it is possible that sex
differences observed in various measures of visuospatial
ability reflect differences in cognition rather than in
vision, which again highlights the requirement for addi-
tional studies of sex differences in human perception and
cognition in general.
CONCLUSIONS
This Mini-Review presents considerable evidence in sup-
port of the thesis that females and males see the world dif-
ferently and that this reflects corresponding sex
differences in the human visual system. We seek not to
evaluate scientific reports of sex differences in human
vision critically but rather to show that, if any single result
reported here is valid, sex differences in the human visual
system are undeniable. We concede that the portions of
the visual system discussed here are a mere subset of a
neurally widespread visual system. If anything, this
emphasizes the requirement for additional research on sex
differences at all levels of the visual system. Additionally,
the fact that disorders such as autism and schizophrenia
are more prevalent in males than in females implies that
there are corresponding sex differences in visual function
because these disorders are frequently associated with
abnormal visual processing, even at very basic levels
(Behrmann et al., 2006; Butler et al., 2008; Simmons
et al., 2009; Silverstein et al., 2015). In short, sex differ-
ences in the human visual system, although controversial,
are undeniable. Additional investigation of sex differences
in the human visual system would contribute to an
already considerable amount of evidence in support of sex
differences in the nervous system generally and strongly
counter the traditional assumption in many fields of neu-
roscience research that sex differences are negligible or
nonexistent (Cahill, 2006; Cahill and Aswad, 2015).
CONFLICT OF INTEREST STATEMENT
The authors have no conflicts of interest.
Visual System Sex Differences 621
Journal of Neuroscience Research
ROLE OF AUTHORS
The authors take equal responsibility for the research and
writing of this Mini-Review. Literature review: JEV, LS.
Drafting of the manuscript: JEV, LS. Critical revision of
the Mini-Review for important intellectual content: JEV,
LS.
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Visual System Sex Differences 625
Journal of Neuroscience Research
... As a result, differences in gender-based color perception and assessment may exist regarding lipsticks. Additionally, differences in color vision between men and women have been extensively reported in studies from multiple disciplines, including genetics (Vanston and Strother, 2017), neuroscience (Palmer et al., 2013;Alfano et al., 2023;Young et al., 2023), ophthalmology (Panorgias et al., 2010), and biology (Hurlbert and Ling, 2007;Schwarzkopf et al., 2011). For instance, evidence related to gender differences was found in androgen receptors, estrogen, and genes on the X chromosome (Neitz and Neitz, 2011;Vanston and Strother, 2017). ...
... Additionally, differences in color vision between men and women have been extensively reported in studies from multiple disciplines, including genetics (Vanston and Strother, 2017), neuroscience (Palmer et al., 2013;Alfano et al., 2023;Young et al., 2023), ophthalmology (Panorgias et al., 2010), and biology (Hurlbert and Ling, 2007;Schwarzkopf et al., 2011). For instance, evidence related to gender differences was found in androgen receptors, estrogen, and genes on the X chromosome (Neitz and Neitz, 2011;Vanston and Strother, 2017). Therefore, we sought to explore potential sex-related variations in lipstick color perception. ...
... Moreover, physiological distinctions in color vision between genders have also been documented. Studies indicate that inherent variations exist in retinal physiology and visual cortical processing between males and females (Vanston and Strother, 2017). The genes on the X chromosome have been found to determine the spectral sensitivities of many photoreceptors in the retina (Neitz and Neitz, 2011). ...
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Lipstick is one of the most commonly used cosmetics, which is closely associated with female attractiveness and influences people’s perception and behavior. This study aimed to investigate the impact of light sources, lipstick colors, as well as gender on the subjective assessment of lipstick color products from the prospective of color preference, purchase intention and sexual attractiveness. The correlation between color preference evaluations when applying lipstick on lips and on forearms was also explored. Sixty participants completed their visual assessment of 15 lipsticks worn by 3 models under 5 light sources, with uniformly sampled correlated color temperature (CCT) values ranging from 2,500 K to 6,500 K. The results indicated that the light source significantly influenced color preference and purchase intention, while lipstick color significantly impacted on sexual attractiveness. The interactions between gender and other factors were also observed and are discussed. Compared to men, women were found to be more sensitive to different light sources and hold different attitudes toward different lipstick colors under different CCTs. Interestingly, no significant correlation was found between lipstick color preference ratings on the lips and forearm, which conflicted with the commonly recognized way of lipstick color selection. These findings should contribute to a deeper understanding of the consumer attitude toward lipstick colors and provide a useful reference for lighting design in situations where cosmetics are specified, manufactured, retailed and generally used, both professionally and in the home.
... One hypothesis for this gender-specific effect is related to potential differences in visual processing and sensitivity to blue light between the sexes. It is known that there are inherent variations in retinal physiology and visual system development between males and females [35,36]. These differences may influence how the retinal cells respond to blue light exposure and subsequently impact color discrimination in the tritan axis. ...
... While research in this area is still limited and controversial, it has been reported that males tend to have better visual acuity than females, while females tend to have better color discrimination ability [41]. Other studies have found sex differences in visual processing speed, contrast sensitivity, and visual attention, though the results have been mixed and may depend on the specific task and population studied [36,42,43]. Some researchers have proposed that the observed sex differences in visual function may be attributed to biological factors (e.g., sex hormones and brain structure) and sociocultural influences (e.g., gender roles and experiences) [35,36]. ...
... Other studies have found sex differences in visual processing speed, contrast sensitivity, and visual attention, though the results have been mixed and may depend on the specific task and population studied [36,42,43]. Some researchers have proposed that the observed sex differences in visual function may be attributed to biological factors (e.g., sex hormones and brain structure) and sociocultural influences (e.g., gender roles and experiences) [35,36]. Nevertheless, more research is required to fully understand the mechanisms underlying these differences and their implications for visual health and development. ...
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Excessive screen time has been linked to adverse health outcomes in children, including vision-related problems such as myopia. However, very few studies have evaluated the effect of moderate screen exposure on the development of visual functions. This study aimed to examine the association between screen time during middle childhood and color discrimination, contrast sensitivity, and short-range visual acuity in 12-year-old children (n = 305) from the mother–child PELAGIE cohort (France) for the whole sample and for boys and girls separately. Visual functions were assessed using the Freiburg Acuity and Contrast Test and an adapted version of the Cambridge Color Test. Screen exposure was documented using a parent self-report questionnaire. Regression models showed that screen exposure at 6 years of age was significantly associated with higher contrast sensitivity across the entire sample at 12 years of age. However, when controlling for covariates, this association remained statistically significant in girls only. Sex-stratified analyses also showed that moderate screen exposure was linked to improved tritan-axis color vision in boys only. These findings suggest that moderate screen exposure in middle childhood is not harmful to visual function development and as such, provide new insights into the impact of digital technology on children’s visual health and development.
... Previous research has shown various differences in the visual system across the sexes, as females tend to prioritize the utilization of low spatial frequencies, which convey information regarding the overall structure of objects, while males exhibit a segregative approach that emphasizes individual objects and intricate details [49]. • ...
... Specifically, there are 94 connections between these subnetworks in pre-adolescence. Based on previous studies, females have shown greater hyperconnectivity in the DMN compared to males [44,45,49]. Our work provides further insight into where the subnetwork connections exist during different stages of adolescence. ...
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Background: A fundamental grasp of the variability observed in healthy individuals holds paramount importance in the investigation of neuropsychiatric conditions characterized by sex-related phenotypic distinctions. Functional magnetic resonance imaging (fMRI) serves as a meaningful tool for discerning these differences. Among deep learning models, graph neural networks (GNNs) are particularly well-suited for analyzing brain networks derived from fMRI blood oxygen level-dependent (BOLD) signals, enabling the effective exploration of sex differences during adolescence. Method: In the present study, we introduce a multi-modal graph isomorphism network (MGIN) designed to elucidate sex-based disparities using fMRI task-related data. Our approach amalgamates brain networks obtained from multiple scans of the same individual, thereby enhancing predictive capabilities and feature identification. The MGIN model adeptly pinpoints crucial subnetworks both within and between multi-task fMRI datasets. Moreover, it offers interpretability through the utilization of GNNExplainer, which identifies pivotal sub-network graph structures contributing significantly to sex group classification. Results: Our findings indicate that the MGIN model outperforms competing models in terms of classification accuracy, underscoring the benefits of combining two fMRI paradigms. Additionally, our model discerns the most significant sex-related functional networks, encompassing the default mode network (DMN), visual (VIS) network, cognitive (CNG) network, frontal (FRNT) network, salience (SAL) network, subcortical (SUB) network, and sensorimotor (SM) network associated with hand and mouth movements. Remarkably, the MGIN model achieves superior sex classification accuracy when juxtaposed with other state-of-the-art algorithms, yielding a noteworthy 81.67% improvement in classification accuracy. Conclusion: Our model’s superiority emanates from its capacity to consolidate data from multiple scans of subjects within a proven interpretable framework. Beyond its classification prowess, our model guides our comprehension of neurodevelopment during adolescence by identifying critical subnetworks of functional connectivity.
... In light of the thoroughly researched relationship between the eye and the brain [1][2][3][4], sex differences in brain size have been hypothesised [5] to be associated with reports of sexual dimorphism in visual perception. Interestingly, lateral hemisphere activation during visual perception tasks was found to be independent of sex, handedness, and ocular dominance [6], the latter being associated with interocular retinal thickness asymmetries [7]. ...
... The relationship between various retinopathies and gonadal hormones has been addressed, as in [26,27], where the authors highlighted the role of sex hormones on the pathophysiology of ocular disorders, such as age-related macular degeneration and diabetic retinopathy. Despite the possible connection between gonadal hormones and the health/disease status of the retina, the intricate interplay between sex and vision both in healthy individuals and across different disease processes [5] suggests that observed sex differences in the retina cannot be attributed to a single mechanism [28]. ...
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Background: Retinal texture has gained momentum as a source of biomarkers of neurodegeneration, as it is sensitive to subtle differences in the central nervous system from texture analysis of the neuroretina. Sex differences in the retina structure, as detected by layer thickness measurements from optical coherence tomography (OCT) data, have been discussed in the literature. However, the effect of sex on retinal interocular differences in healthy adults has been overlooked and remains largely unreported. Methods: We computed mean value fundus images for the neuroretina layers as imaged by OCT of healthy individuals. Texture metrics were obtained from these images to assess whether women and men have the same retina texture characteristics in both eyes. Texture features were tested for group mean differences between the right and left eye. Results: Corrected texture differences exist only in the female group. Conclusions: This work illustrates that the differences between the right and left eyes manifest differently in females and males. This further supports the need for tight control and minute analysis in studies where interocular asymmetry may be used as a disease biomarker, and the potential of texture analysis applied to OCT imaging to spot differences in the retina.
... Visual stimuli account for more than 80 percent of the information received when our eyes are open, and nearly 50 percent of nerve fibers are directly or indirectly associated with the retina (Medina and Hanlon, 2009;Lee et al., 2020). The visual system primarily focuses on contrast, color, and movement changes, all of which have the potential to influence human behavior (Vanston and Strother, 2017). Therefore, studying the visual system is crucial for unraveling the workings of the brain. ...
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Orientation detection is an essential function of the visual system. In our previous works, we have proposed a new orientation detection mechanism based on local orientation-selective neurons. We assume that there are neurons solely responsible for orientation detection, with each neuron dedicated to detecting a specific local orientation. The global orientation is inferred from the local orientation information. Based on this mechanism, we propose an artificial visual system (AVS) by utilizing a single-layer of McCulloch-Pitts neurons to realize these local orientation-sensitive neurons and a layer of sum pooling to realize global orientation detection neurons. We demonstrate that such a single-layer perceptron artificial visual system (AVS) is capable of detecting global orientation by identifying the orientation with the largest number of activated orientation-selective neurons as the global orientation. To evaluate the effectiveness of this single-layer perceptron AVS, we perform computer simulations. The results show that the AVS works perfectly for global orientation detection, aligning with the majority of physiological experiments and models. Moreover, we compare the performance of the single-layer perceptron AVS with that of a traditional convolutional neural network (CNN) on orientation detection tasks. We find that the single-layer perceptron AVS outperforms CNN in various aspects, including identification accuracy, noise resistance, computational and learning cost, hardware implementation feasibility, and biological plausibility.
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Gradient colors are widely used in product design. The variation of gradient colors muting a color as a series of steps from bright to dull creates a soft and gradual impression while also affecting people's perceptions. This study manipulates the types of gradient colors to explore the relationship between color gradients and perception of stability to determine whether weight perception plays a role. In the case of controlling for aesthetic differences, the study manipulated two types of color gradients (dark colors fading upward from the bottom versus downward from the top) and measured the perceptions of product stability. In the same hue, an upward gradient gives a stronger perception of stability. In addition, gradient colors significantly influence women's perception of stability more than men's. The study also investigated the mediating effect of weight perception: participants evaluated color fading-upward products with less weight relative to fading-downward colors. Furthermore, dark colors fading upward from the bottom lead to a stronger perception of weight, increasing the stability perception of the object. Finally, to aid future research, we discuss the practical implications of the current findings for areas such as sensory marketing, as well as possible directions for future research.
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This study investigates bistable perception as a function of the presentation side of the ambiguous figures and of participants' sex, to evaluate left-right hemispheric (LH-RH) asymmetries related to consciousness. In two experiments using the divided visual field paradigm, two Rubin's vase-faces figures were projected simultaneously and continuously 180 s long to the left (LVF) and right (RVF; Experiment 1) or to the upper (UVF) and lower (DVF; Experiment 2) visual hemifields of 48 healthy subjects monitored with eye-tracker. Experiment 1 enables stimulus segregation from the LVF to the RH and from the RVF to the LH, whereas Experiment 2 does not. Results from Experiment 1 show that males perceived the face profiles for more time in the LVF than in the RVF, with an opposite trend for the vase, whereas females show a similar pattern of perception in the two hemifields. A related result confirmed the previously reported possibility to have simultaneously two different percepts (qualia) in the two hemifields elicited by the two identic ambiguous stimuli, which was here observed to occur more frequently in males. Similar effects were not observed in Experiment 2. These findings suggest that the percepts display the processing abilities of the hemisphere currently processing the stimulus eliciting them (e.g., RH-faces), and that females and males reflect in bistable perception, a genuine manifestation of consciousness, the well-known hemispheric asymmetry differences they show in ordinary perception.
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Event-related potentials (ERPs) were recorded in 26 right-handed students while they detected pictures of animals intermixed with those of familiar objects, faces and faces-in-things (FITs). The face-specific N170 ERP component over the right hemisphere was larger in response to faces and FITs than to objects. The vertex positive potential (VPP) showed a difference in FIT encoding processes between males and females at frontal sites; while for men, the FIT stimuli elicited a VPP of intermediate amplitude (between that for faces and objects), for women, there was no difference in VPP responses to faces or FITs, suggesting a marked anthropomorphization of objects in women. SwLORETA source reconstructions carried out to estimate the intracortical generators of ERPs in the 150 to 190 ms time window showed how, in the female brain, FIT perception was associated with the activation of brain areas involved in the affective processing of faces (right STS, BA22; posterior cingulate cortex, BA22; and orbitofrontal cortex, BA10) in addition to regions linked to shape processing (left cuneus, BA18/30). Conversely, in the men, the activation of occipito/parietal regions was prevalent, with a considerably smaller activation of BA10. The data suggest that the female brain is more inclined to anthropomorphize perfectly real objects compared to the male brain.
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We perceive color everywhere and on everything that we encounter in daily life. Color science has progressed to the point where a great deal is known about the mechanics, evolution, and development of color vision, but less is known about the relation between color vision and psychology. However, color psychology is now a burgeoning, exciting area and this Handbook provides comprehensive coverage of emerging theory and research. Top scholars in the field provide rigorous overviews of work on color categorization, color symbolism and association, color preference, reciprocal relations between color perception and psychological functioning, and variations and deficiencies in color perception. The Handbook of Color Psychology seeks to facilitate cross-fertilization among researchers, both within and across disciplines and areas of research, and is an essential resource for anyone interested in color psychology in both theoretical and applied areas of study.
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Functional MRI was used to investigate sex differences in brain activation during a paradigm similar to a lexical-decision task. Six males and 6 females performed two runs of the lexical visual field task (i.e., deciding which visual field a word compared with a pseudoword was presented to). A sex difference was noted behaviorally: The reaction time data showed males had a marginal right visual field advantage and women a left visual field advantage. Imaging results showed that men had a strongly left-lateralized pattern of activation, e.g., inferior frontal and fusiform. gyrus, while women showed a more symmetrical pattern in language related areas with greater right-frontal and right-middle-temporal activation. The data show evidence of task-specific sex differences in the cerebral organization of language processing. (C) 2002 Elsevier Science.
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In 23 fMRI studies on six subjects, we examined activation in visual and motor tasks. We modeled the expected activation time course by convolving a temporal description of the behavioral task with an empirically determined impulse response function. We evaluated the signal activation intensity as both the number of activated voxels over arbitrary correlation thresholds and as the slope of the regression line between our modeled time course and the actual data. Whereas the voxel counting was strikingly unstable (standard deviation 74% in visual trials at a correlation of 0.5), the slope was relatively constant across trials and subjects (standard deviation < 14%). Using Monte Carlo methods, we determined that the measured slope was largely Independent of the contrast-to-noise ratio. Voxel counting is a poor proxy for activation intensity, with greatly increased scatter, much reduced statistical power, and increased type II error. The data support an alternative approach to functional magnetic resonance imaging (fMRI) that allows for quantitative comparisons of fMRI response magnitudes across trials and laboratories. J. Magn Reson. Imaging 1999; 10:33-40. (C) 1999 Wiley-Liss, Inc.
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The issue of sex influences on the brain is rapidly moving center stage, driven by abundant results proving that subject sex can and regularly does alter, negate, and even reverse neuroscientific findings and conclusions down to the molecular level and thus can no longer be justifiably marginalized or ignored.
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Reading requires the neural integration of visual word form information that is split between our retinal hemifields. We examined multiple visual cortical areas involved in this process by measuring fMRI responses while observers viewed words that changed or repeated in one or both hemifields. We were specifically interested in identifying brain areas that exhibit decreased fMRI responses as a result of repeated versus changing visual word form information in each visual hemifield. Our method yielded highly significant effects of word repetition in a previously reported visual word form area (VWFA) in occipitotemporal cortex, which represents hemifield-split words as whole units. We also identified a more posterior occipital word form area (OWFA), which represents word form information in the right and left hemifields independently and is thus both functionally and anatomically distinct from the VWFA. Both the VWFA and the OWFA were left-lateralized in our study and strikingly symmetric in anatomical location relative to known face-selective visual cortical areas in the right hemisphere. Our findings are consistent with the observation that category-selective visual areas come in pairs and support the view that neural mechanisms in left visual cortex-especially those that evolved to support the visual processing of faces-are developmentally malleable and become incorporated into a left-lateralized visual word form network that supports rapid word recognition and reading.