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Losing your Head: Behavioral and Electrophysiological Effects of Body Inversion
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The present study aimed to further explore the mechanisms underlying the perception of human body shapes. Behavioral and electrophysiological inversion effects were studied for human bodies with and without heads and for animal bodies (cats, dogs, and birds). Recognition of human bodies (with heads) was adversely affected by stimulus inversion, and the N170 had longer latencies and higher amplitudes for inverted compared to upright human bodies. Human body shapes presented without heads yielded the opposite result pattern. The data for animal bodies did not yield consistent effects. Taken together, the present findings suggest that human bodies might be processed by specialized cortical mechanisms which are at least partly dissociable from mechanisms involved in object or face processing.
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... Faces reliably elicit an ERP component referred to as the N170 [16], for example, while bodies elicit a similar component referred to as the N190 [17]. Both of these ERP components exhibit clear inversion effects [18,19], linking the behavioral results described above to specific neural mechanisms. Further, evidence from intracranial recordings [20] and patterns of response to stimuli depicting different body parts [21] indicate good correspondence between the body-selective ERP responses and activity in the extrastriate cortical areas selective for body stimuli [20]. ...
... We were able to observe a consistent body inversion effect across all conditions, with the amplitude of the N190 significantly reduced, delayed, and potentially diffused by inverted images of bodies. The effect we observed with regard to amplitude is intriguing in that there are reports of both a classic inversion effect for body images in which the amplitude of the N190 is increased (becomes more negative) subject to body inversion (see [19,46,47] and an "inverted" inversion effect in which the amplitude is reduced [19]. This latter outcome has been linked to the absence of heads and/or eyes in body images [48], which may indicate that the enhancement of the N190 ...
... We were able to observe a consistent body inversion effect across all conditions, with the amplitude of the N190 significantly reduced, delayed, and potentially diffused by inverted images of bodies. The effect we observed with regard to amplitude is intriguing in that there are reports of both a classic inversion effect for body images in which the amplitude of the N190 is increased (becomes more negative) subject to body inversion (see [19,46,47] and an "inverted" inversion effect in which the amplitude is reduced [19]. This latter outcome has been linked to the absence of heads and/or eyes in body images [48], which may indicate that the enhancement of the N190 ...
The N190 is a body-sensitive ERP component that responds to images of human bodies in different poses. In natural settings, bodies vary in posture and appear within complex, cluttered environments, frequently with other people. In many studies, however, such variability is absent. How does the N190 response change when observers see images that incorporate these sources of variability? In two experiments (N = 16 each), we varied the natural appearance of upright and inverted bodies to examine how the N190 amplitude, latency, and the Body-Inversion Effect (BIE) were affected by natural variability. In Experiment 1, we varied the number of people present in upright and inverted naturalistic scenes such that only one body, a subitizable number of bodies, or a “crowd” was present. In Experiment 2, we varied the natural body appearance by presenting bodies either as silhouettes or with photographic detail. Further, we varied the natural background appearance by either removing it or presenting individual bodies within a rich environment. Using component-based analyses of the N190, we found that the number of bodies in a scene reduced the N190 amplitude, but didn’t affect the BIE (Experiment 1). Naturalistic body and background appearance (Experiment 2) also affected the N190, such that component amplitude was dramatically reduced by naturalistic appearance. To complement this analysis, we examined the contribution of spatiotemporal features (i.e., electrode × time point amplitude) via SVM decoding. This technique allows us to examine which timepoints across the entire waveform contribute the most to successful decoding of body orientation in each condition. This analysis revealed that later timepoints (after 300ms) contribute most to successful orientation decoding. These results demonstrate that natural appearance variability affects body processing at the N190 and that later ERP components may make important contributions to body processing in natural scenes.
... Previous studies have also highlighted the important influence of views on the recognition of human faces (Almeida et al., 2020;Foster et al., 2022;Goeleven et al., 2008;Thoma et al., 2013) and bodies (Foster et al., 2022;Gross et al., 2012;He et al., 2020;Moors et al., 2015;Pollux et al., 2019;Thoma et al., 2013). Although Alaerts et al. (2011) considered this factor of view, they did not collect kinematic data of the head-a key point in the perception of the human body (Arizpe et al., 2017;Brandman & Yovel, 2010;Minnebusch et al., 2009;Yovel et al., 2010) and emotional body movement (Witkower & Tracy, 2019). (3) The DEMOS has four mainstream indicators (i.e., recognition accuracy, emotional intensity, subjective movement, and objective movement) in the field of emotional biological motion, which is beneficial for researchers to directly consider and control in their studies. ...
... Note that Alaerts et al. (2011) did not find significant differences in recognition accuracy for emotional PLDs among the same three views, presumably because their PLDs did not include the head, which is an important factor in the recognition of emotional body movement. The head plays a key role in holistic body processing (Arizpe et al., 2017;Brandman & Yovel, 2010;Minnebusch et al., 2009;Yovel et al., 2010) and emotional body coding (Witkower & Tracy, 2019). Head orientation also serves as a significant cue in the judgment of emotion (Dael et al., 2012b;Ekman & Friesen, 1967;Van Cappellen & Edwards, 2021). ...
Human body movements are important for emotion recognition and social communication and have received extensive attention from researchers. In this field, emotional biological motion stimuli, as depicted by point-light displays, are widely used. However, the number of stimuli in the existing material library is small, and there is a lack of standardized indicators, which subsequently limits experimental design and conduction. Therefore, based on our prior kinematic dataset, we constructed the Dalian Emotional Movement Open-source Set (DEMOS) using computational modeling. The DEMOS has three views (i.e., frontal 0°, left 45°, and left 90°) and in total comprises 2664 high-quality videos of emotional biological motion, each displaying happiness, sadness, anger, fear, disgust, and neutral. All stimuli were validated in terms of recognition accuracy, emotional intensity, and subjective movement. The objective movement for each expression was also calculated. The DEMOS can be downloaded for free from https://osf.io/83fst/ . To our knowledge, this is the largest multi-view emotional biological motion set based on the whole body. The DEMOS can be applied in many fields, including affective computing, social cognition, and psychiatry.
... This result suggested that participants might apply configural processing, likewise to faces, to recognize human body postures. Other studies have found similar results using different types of body stimulus materials, including gray-scale figures (Arizpe et al., 2017;Brandman & Yovel, 2010;Minnebusch et al., 2009;Yovel et al., 2010), point-light sequences (Chang & Troje, 2009;Troje & Westhoff, 2006), and 3D human body posture figures (Tao & Sun, 2013;Tao et al., 2014). Moreover, event-related potential (ERP) investigations for inverted body postures also revealed similar changes in the N170 component compared with inverted faces (Mohamed et al., 2011;Stekelenburg & de Gelder, 2004;Tao et al., 2014), which supports the idea that the processing of body postures is the same as that of faces. ...
... However, the results of studies involving head manipulations were not consistent (Mohamed et al., 2011;Tao et al., 2014;Yovel et al., 2010). According to an ERP study (Minnebusch et al., 2009), electrophysiological results showed that the inversion effect of bodies without heads was opposite to that with heads. Specifically compared to the upright bodies without heads, inverted ones revealed the improved performance and elicited a reduced N170 amplitude. ...
Some researchers argue that holistic processing is unique to face recognition supported by the face inversion effect. However, findings such as the body inversion effect challenge the face processing-specificity hypothesis, thus supporting the expertise hypothesis. Few studies have explored a possible hand inversion effect which could involve special processing similar to the face and body. We conducted four experiments to investigate the time course and flexibility of the hand posture inversion effect. We utilized a same/different discrimination task (Experiments 1 and 2), an identification task (Experiment 3), and a training paradigm involving the exposure of different hand orientations (Experiment 4). The results show the hand posture inversion effect (with fingers up as upright orientation) was not initially observed during the early phase of testing, but occurred in later phases. This suggests that both lifetime experience and recent exposure affect the hand posture inversion effect. We also found the hand posture inversion effect, once established, was stable across days and remained consistent across different tasks. In addition, the hand posture inversion effect for specific orientations could be obtained with short-term training of a given orientation, indicating the cognitive process is flexible.
... No gaps were left between the lower and upper body parts so that we avoided discontinuities in body figures that could interfere with the composite illusion effect (Robbins & Coltheart, 2012b;Soria Bauser et al., 2011). Because previous studies documented reduced (Robbins & Coltheart, 2012a) or absent inversion effects for headless bodies (Minnebusch et al., 2009;Yovel et al., 2010), we used blurred faces so as to maintain the head and to avoid face identity recognition . Notably, the paired stimuli of each trial had the same orientation and alignment, but different lower parts, whereas the upper parts could be either the same or different. ...
... Although the body inversion effect has been widely demonstrated in literature (Gillmeister et al., 2019;Minnebusch & Daum, 2009;Reed et al., 2006), few studies have documented the composite illusion for body stimuli (Vrancken et al., 2017;Figure 2 Rate Correct Score (RCS) of Each Condition for the Adult (Upper Panel) and the Child Groups (Lower Panel) During the Discrimination of Adult (grey) and Child (white) Stimuli Note. Bars indicate SEM of measurements. ...
There is inconsistent evidence that human bodies are processed through holistic processing as it has been widely reported for faces. To assess how configural and holistic processes may develop with age, we administered a visual body recognition task assessing the presence of body inversion and composite illusion effects to white adults (114 participants, 77 women, aged between 18 and 35 years) and children (138 participants, 74 girls, aged between 6 and 11 years). Furthermore, to verify the presence of an own-age bias in body processing, we presented either child or adult bodies to both age groups. Adults and children showed reliable and comparable body inversion and composite illusion effects, confirming the use of configural and holistic body processing. Cross-sectional analysis showed that these perceptual strategies were already reliable in children aged 6-7 years and did not encounter significant changes across childhood. Although we found reliable body inversion and composite illusion effects for both own- and different-age bodies, results pointed to greater composite illusion effects for own-age bodies. This may suggest that sharing similar body structures might facilitate the holistic processing of others' bodies. These findings provide new insights into the development of body-specific perceptual processes and may have theoretical and clinical implications for the evaluation and treatment of body perception disorders in childhood. (PsycInfo Database Record (c) 2022 APA, all rights reserved).
... However, our study extends these findings by showing that this neural activity is increased for the images of hands performing erroneous actions. Enhanced occipito-temporal N1 has been previously reported during the perception of body-schema violations, such as inverted body orientation (Minnebusch et al., 2010;Minnebusch et al., 2008;Orlandi and Proverbio, 2020) and observation of incongruent hand actions (Bortoletto et al., 2011). Bortoletto et al. (2011) suggested that high-level visual processing of hand actions might integrate at an early latency the information concerning intended actions coded from the motor system. ...
Monitoring the motor performance of others, including the correctness of their actions, is crucial for the human behavior. However, while performance (and error) monitoring of the own actions has been studied extensively at the neurophysiological level, the corresponding studies on monitoring of others' errors are scarce, especially for ecological actions. Moreover, the role of the context of the observed action has not been sufficiently explored. To fill this gap, the present study investigated electroencephalographic (EEG) indices of error monitoring during observation of images of interrupted reach-to-grasp actions in social (an object held in another person's hand) and non-social (an object placed on a table) contexts. Analysis in time- and time-frequency domain showed that, at the level of conscious error awareness, there were no effects of the social context (observed error positivity was present for erroneous actions in both contexts). However, the effects of the context were present at the level of hand image processing: observing erroneous actions in the non-social context was related to larger occipito-temporal N1 and theta activity, while in the social context this pattern was reversed, i.e., larger N1 and theta activity were present for the correct actions. These results suggest that, in case of easily predictable ecological actions, action correctness is processed as early as at the level of hand image perception, since the hand posture conveys information about the action (e.g., motor intention). The social context of actions might make the correct actions more salient, possibly through the saliency of the correctly achieved common goal.
... Compared to identifying objects, the recognition of human faces and bodies engages special perceptual processes and neural mechanisms [9,10]. Indeed, faces and bodies seem attributes, such as body postures and movements [33][34][35]. ...
Body inversion effects (BIEs) reflect the deployment of the configural processing of body stimuli. BIE modulates the activity of body-selective areas within both the dorsal and the ventral streams, which are tuned to low (LSF) or high spatial frequencies (HSF), respectively. The specific contribution of different bands to the configural processing of bodies along gender and posture dimensions, however, is still unclear. Seventy-two participants performed a delayed matching-to-sample paradigm in which upright and inverted bodies, differing for gender or posture, could be presented in their original intact form or in the LSF-or HSF-filtered version. In the gender discrimination task, participants' performance was enhanced by the presentation of HSF images. Conversely, for the posture discrimination task, a better performance was shown for either HSF or LSF images. Importantly, comparing the amount of BIE across spatial-frequency conditions, we found greater BIEs for HSF than LSF images in both tasks, indicating that configural body processing may be better supported by HSF information, which will bias processing in the ventral stream areas. Finally, the exploitation of HSF information for the configural processing of body postures was lower in individuals with higher autistic traits, likely reflecting a stronger reliance on the local processing of body-part details.
Neuroscientific research on emotion has developed dramatically over the past decade. The cognitive neuroscience of human emotion, which has emerged as the new and thriving area of 'affective neuroscience', is rapidly rendering existing overviews of the field obsolete. This handbook provides a comprehensive, up-to-date and authoritative survey of knowledge and topics investigated in this cutting-edge field. It covers a range of topics, from face and voice perception to pain and music, as well as social behaviors and decision making. The book considers and interrogates multiple research methods, among them brain imaging and physiology measurements, as well as methods used to evaluate behavior and genetics. Editors Jorge Armony and Patrik Vuilleumier have enlisted well-known and active researchers from more than twenty institutions across three continents, bringing geographic as well as methodological breadth to the collection. This timely volume will become a key reference work for researchers and students in the growing field of neuroscience.
Neuroscientific research on emotion has developed dramatically over the past decade. The cognitive neuroscience of human emotion, which has emerged as the new and thriving area of 'affective neuroscience', is rapidly rendering existing overviews of the field obsolete. This handbook provides a comprehensive, up-to-date and authoritative survey of knowledge and topics investigated in this cutting-edge field. It covers a range of topics, from face and voice perception to pain and music, as well as social behaviors and decision making. The book considers and interrogates multiple research methods, among them brain imaging and physiology measurements, as well as methods used to evaluate behavior and genetics. Editors Jorge Armony and Patrik Vuilleumier have enlisted well-known and active researchers from more than twenty institutions across three continents, bringing geographic as well as methodological breadth to the collection. This timely volume will become a key reference work for researchers and students in the growing field of neuroscience.
Neuroscientific research on emotion has developed dramatically over the past decade. The cognitive neuroscience of human emotion, which has emerged as the new and thriving area of 'affective neuroscience', is rapidly rendering existing overviews of the field obsolete. This handbook provides a comprehensive, up-to-date and authoritative survey of knowledge and topics investigated in this cutting-edge field. It covers a range of topics, from face and voice perception to pain and music, as well as social behaviors and decision making. The book considers and interrogates multiple research methods, among them brain imaging and physiology measurements, as well as methods used to evaluate behavior and genetics. Editors Jorge Armony and Patrik Vuilleumier have enlisted well-known and active researchers from more than twenty institutions across three continents, bringing geographic as well as methodological breadth to the collection. This timely volume will become a key reference work for researchers and students in the growing field of neuroscience.
Face and body perception rely on specialized processing mechanisms to interpret social information efficiently. The body inversion effect (BIE), refers to an inversion effect for bodies, such that recognition of bodies is impaired by inversion. The BIE, like the face inversion effect (FIE), is particularly important because a disproportionate BIE relative to inversion effects for objects could be interpreted in much the same way as the disproportionate FIE has often been characterized; that is, as evidence of specialized, configural processing. However, research supporting the BIE is marked by methodological heterogeneity and mixed findings. Our multilevel Bayesian meta-analysis addresses inconsistencies in the literature by pooling data from numerous studies to estimate the magnitude of the BIE across various methodological and stimulus properties. We included 180 effect sizes from 41 empirical articles representing data from 2,274 participants. Overall, we found that the BIE was moderate-large in magnitude (Hedges' g = 0.75). Importantly, the inversion effect was larger for bodies than objects (b = 0.42); however, the inversion effect for faces was larger than for bodies (b = 0.34). We tested the role of discrimination dimension, stimulus type, face/head inclusion, stimulus sexualization, and sexualized stimulus sex as moderators of the BIE. We found that the BIE was moderated by discrimination dimension, stimulus type, stimulus sexualization, and sexualized stimulus sex. By synthesizing the existing literature, we provide a better theoretical understanding of how underlying visual processing mechanisms may differ for different types of social information (i.e., bodies vs. faces).
Behavioral studies have shown that picture-plane inversion impacts face and object recognition differently, thereby suggesting face-specific processing mechanisms in the human brain. Here we used event-related potentials to investigate the time course of this behavioral inversion effect in both faces and novel objects. ERPs were recorded for 14 subjects presented with upright and inverted visual categories, including human faces and novel objects (Greebles). A N170 was obtained for all categories of stimuli, including Greebles. However, only inverted faces delayed and enhanced N170 (bilaterally). These observations indicate that the N170 is not specific to faces, as has been previously claimed. In addition, the amplitude difference between faces and objects does not reflect face-specific mechanisms since it can be smaller than between non-face object categories. There do exist some early differences in the time-course of categorization for faces and non- faces across inversion. This may be attributed either to stimulus category per se (e.g. face-specific mechanisms) or to differences in the level of expertise between these categories.
Inversion and photographic negation both impair face recognition. Inversion seems to disrupt processing of the spatial relationship between facial features ('relational' processing) which normally occurs with upright faces and which facilitates their recognition. It remains unclear why negation affects recognition. To find out if negation impairs relational processing, we investigated whether negative faces are subject to the 'chimeric-face effect'. Recognition of the top half of a composite face (constructed from top and bottom halves of different faces) is difficult when the face is upright, but not when it is inverted. To perform this task successfully, the bottom half of the face has to be disregarded, but the relational processing which normally occurs with upright faces makes this difficult. Inversion reduces relational processing and thus facilitates performance on this particular task. In our experiments, subjects saw pairs of chimeric faces and had to decide whether or not the top halves were identical. On half the trials the two chimeras had identical tops; on the remaining trials the top halves were different. (The bottom halves were always different.) All permutations of orientation (upright or inverted) and luminance (normal or negative) were used. In experiment 1, each pair of 'identical' top halves were the same in all respects. Experiment 2 used differently oriented views of the same person, to preclude matches being based on incidental features of the images rather than the faces displayed within them. In both experiments, similar chimeric-face effects were obtained with both positive and negative faces, implying that negative faces evoke some form of relational processing. It is argued that there may be more than one kind of relational processing involved in face recognition: the 'chimeric-face effect' may reflect an initial 'holistic' processing which binds facial features into a 'Gestalt', rather than being a demonstration of the configurational processing involved in individual recognition.
Event-related potentials (ERPs) associated with face perception were recorded with scalp electrodes from normal volunteers. Subjects performed a visual target detection task in which they mentally counted the number of occurrences of pictorial stimuli from a designated category such us butterflies. In separate experiments, target stimuli were embedded within a series of other stimuli including unfamiliar human faces and isolated face components, inverted faces, distorted faces, animal faces, and other nonface stimuli. Unman faces evoked a negative potential at 172 msec (N170), which was absent from the ERPs elicited by other animate and inanimate nonface stimuli. N170 was largest over the posterior temporal scalp and was larger over the right than the left hemisphere. N170 was delayed when faces were presented upside-down, but its amplitude did not change. When presented in isolation, eyes elicited an N170 that was significantly larger than that elicited by whole faces, while noses and lips elicited small negative ERPs about 50 msec later than N170. Distorted human faces, in which the locations of inner face components were altered, elicited an N170 similar in amplitude to that elicited by normal faces. However, faces of animals, human hands, cars, and items of furniture did not evoke N170. N170 may reflect the operation of a neural mechanism tuned to detect (as opposed to identify) human faces, similar to the "structural encoder" suggested by Bruce and Young (1986). A similar function has been proposed for the face-selective N200 ERP recorded from the middle fusiform and posterior inferior temporal gyri using subdural electrodes in humans (Allison, McCarthy, Nobre, Puce, & Belger, 1994c). However, the differential sensitivity of N170 to eyes in isolation suggests that N170 may reflect the activation of an eye-sensitive region of cortex. The voltage distribution of N170 over the scalp is consistent with a neural generator located in the occipitotemporal sulcus lateral to the fusiform/inferior temporal region that generates N200.
What is it about the way faces are represented by the visual system that makes them so much harder to recognize when inverted? The authors tested the hypothesis that the "face inversion" effect results from the use of holistic shape representations. This suggests that the susceptibility of nonface patterns to inversion should be a function of their degree of part decomposition. In Experiment 1 this was tested and confirmed with dot patterns in which the degree of part decomposition was manipulated by grouping and segregation on the basis of dot color. The hypothesis also predicted that the face inversion effect can be eliminated with face stimuli if participants are induced to recognize the faces in terms of their component parts. In Experiment 2 this was tested and confirmed with whole, intact faces, in which the degree of part decomposition was manipulated by allowing participants to study them, initially, in either whole, intact versions or versions with parts presented separately.
Are faces recognized using more holistic representations than other types of stimuli? Taking holistic representation to mean representation without an internal part structure, we interpret the available evidence on this issue and then design new empirical tests. Based on previous research, we reasoned that if a portion of an object corresponds to an explicitly represented part in a hierarchical visual representation, then when that portion is presented in isolation it will be identified relatively more easily than if it did not have the status of an explicitly represented part. The hypothesis that face recognition is holistic therefore predicts that a part of a face will be disproportionately more easily recognized in the whole face than as an isolated part, relative to recognition of the parts and wholes of other kinds of stimuli. This prediction was borne out in three experiments: subjects were more accurate at identifying the parts of faces, presented in the whole object, than they were at identifying the same part presented in isolation, even though both parts and wholes were tested in a forced-choice format and the whole faces differed only by one part. In contrast, three other types of stimuli--scrambled faces, inverted faces, and houses--did not show this advantage for part identification in whole object recognition.
It was investigated how face inversion affects face-specific components of event-related brain potentials (ERPs) which are assumed to reflect the structural encoding and the recognition of faces. ERPs were recorded to upright and inverted photographs of familiar faces, unfamiliar faces, and houses. In Part I, participants had to detect infrequently presented targets (hands), in Part II, attention was either directed towards or away from the pictorial stimuli. When compared with upright unfamiliar faces, upright familiar faces elicited an enhanced negativity between 300 ms and 450 ms (‘N400f’) and an enhanced positivity between 450 and 650 ms post-stimulus (‘P600f’). It is suggested that these ERP modulations are generated by processes involved in the recognition of faces. Face inversion is known to disrupt face recognition processes. Accordingly, ‘N400f’ and ‘P600f’ were generally absent in response to inverted familiar and unfamiliar faces. The face-specific N170 component at lateral posterior electrodes was not affected by face familiarity, indicating that it reflects processing stages prior to face identification. N170 was delayed and enhanced for inverted relative to upright faces. While N170 enhancements were also observed for inverted relative to upright houses, the N170 latency shift caused by stimulus inversion was face-specific. Directing attention away from the faces towards a demanding primary visual task resulted in an N170 delay for inverted as well as for upright faces, suggesting that the time course of structural encoding of faces is affected by attentional factors. These results demonstrate that ERPs can be used as electrophysiological markers of specialised brain processes underlying the structural encoding and subsequent recognition of faces.
When information about three-dimensional shape obtained from shading and shadows is ambiguous, the visual system favours an interpretation of surface geometry which is consistent with illumination from above. If pictures of top-lit faces are rotated the resulting stimulus is both figurally inverted and illuminated from below. In this study the question of whether the effects of figural inversion and lighting orientation on face recognition are independent or interactive is addressed. Although there was a clear inversion effect for faces illuminated from the front and above, the inversion effect was found to be reduced or eliminated for faces illuminated from below. A strong inversion effect for photographic negatives was also found but in this case the effect was not dependent on the direction of illumination. These findings are interpreted as evidence to suggest that lighting faces from below disrupts the formation of surface-based representations of facial shape.
Using functional magnetic resonance imaging (fMRI), we found an area in the fusiform gyrus in 12 of the 15 subjects tested that was significantly more active when the subjects viewed faces than when they viewed assorted common objects. This face activation was used to define a specific region of interest individually for each subject, within which several new tests of face specificity were run. In each of five subjects tested, the predefined candidate "face area" also responded significantly more strongly to passive viewing of (1) intact than scrambled two-tone faces, (2) full front-view face photos than front-view photos of houses, and (in a different set of five subjects) (3) three-quarter-view face photos (with hair concealed) than photos of human hands; it also responded more strongly during (4) a consecutive matching task performed on three-quarter-view faces versus hands. Our technique of running multiple tests applied to the same region defined functionally within individual subjects provides a solution to two common problems in functional imaging: (1) the requirement to correct for multiple statistical comparisons and (2) the inevitable ambiguity in the interpretation of any study in which only two or three conditions are compared. Our data allow us to reject alternative accounts of the function of the fusiform face area (area "FF") that appeal to visual attention, subordinate-level classification, or general processing of any animate or human forms, demonstrating that this region is selectively involved in the perception of faces.
Bartlett and Searcy's recent account for the Thatcher illusion suggests that inversion impairs holistic facial information. This illusion is used to compare the effects of inverting and negating faces. Subjects made a speeded response to whether just the mouth and the eyes of a face have been inverted. Performance was found to be slower when faces were inverted rather than upright. Presenting faces in photographic negative also hindered performance implying that this transformation also disrupts holistic facial information.
The differential effect of stimulus inversion on face and object recognition suggests that inverted faces are processed by mechanisms for the perception of other objects rather than by face perception mechanisms. We investigated the face inversion using functional magnetic resonance imaging (fMRI). The principal effect of face inversion on was an increased response in ventral extrastriate regions that respond preferentially to another class of objects (houses). In contrast, house inversion did not produce a similar change in face-selective regions. Moreover, stimulus inversion had equivalent, minimal effects for faces in in face-selective regions and for houses in house-selective regions. The results suggest that the failure of face perception systems with inverted faces leads to the recruitment of processing resources in object perception systems, but this failure is not reflected by altered activity in face perception systems.