Serial position effects rapidly distinguish Alzheimer's from frontotemporal dementia.

OBJECTIVE: A significant proportion of patients with behavioural variant frontotemporal dementia (bvFTD) show memory impairments similar to patients with Alzheimer's disease (AD), making them prone to misdiagnosis in early disease stages. Our objective was to establish a rapid and efficient memory measure that enhances discrimination between patients with dementia due to Alzheimer's disease and amnestic presentations of behavioural variant frontotemporal dementia. METHOD: Word list learning data of patients with diagnoses of AD and both amnestic and non-amnestic presentations of bvFTD were analysed. The overall recall rate and the relative contributions of the first two (primacy items) and last two words (recency items) to recall performance were compared between groups. RESULTS: Overall recall rate was indistinguishable between patients with AD and amnestic bvFTD. However, AD patients' recall was mostly driven by recency items, whereas amnestic bvFTD patients' performance was mostly driven by primacy items. CONCLUSION: We conclude that obtaining a simple recency dominance index from a single, 15-item word list memory trial can help discriminate patients with AD from patients with bvFTD, even if they present with similarly severe memory impairment.

An Assessment of Computer-Generated Stimuli for Use in Studies of Body Size Estimation and Bias.

Inaccurate body size judgments are associated with body image disturbances, a clinical feature of many eating disorders. Accordingly, body-related stimuli have become increasingly important in the study of estimation inaccuracies and body image disturbances. Technological advancements in the last decade have led to an increased use of computer-generated (CG) body stimuli in body image research. However, recent face perception research has suggested that CG face stimuli are not recognized as readily and may not fully tap facial processing mechanisms. The current study assessed the effectiveness of using CG stimuli in an established body size estimation task (the "bodyline" task). Specifically, we examined whether employing CG body stimuli alters body size judgments and associated estimation biases. One hundred and six 17- to 25-year-old females completed the CG bodyline task, which involved estimating the size of full-length CG body stimuli along a visual analogue scale. Our results show that perception of body size for CG stimuli was non-linear. Participants struggled to discriminate between extreme bodies sizes and overestimated the size change between near to average bodies. Furthermore, one of our measured size estimation biases was larger for CG stimuli. Our collective findings suggest using caution when employing CG stimuli in experimental research on body perception.

Impressions of sexual unfaithfulness and their accuracy show a degree of universality.

Forming accurate impressions of others' trustworthiness is a critical social skill, with faithfulness representing a key aspect of trust in sexual relationships. Interestingly, there is evidence for a small degree of accuracy in facial impressions of sexual unfaithfulness. Theoretical accounts suggest that these impressions may function to help with partner selection, and may be universal. If so, impressions should be similar for perceivers from different cultures and accuracy should not be limited to own-race faces. We tested these predictions by asking Caucasian and Asian women to judge the likelihood of unfaithfulness from the faces of Caucasian males whose past sexual history was known. In two studies we found high cross-cultural agreement in these impressions, consistent with universality in the impressions themselves. In Study 1, we found an other-race effect in impression accuracy, with significantly less accurate cross-race impressions by Asian women than own-race impressions by Caucasian women. Asian women showed no accuracy. Interestingly, in Study 2, Asian women who had grown up in the West showed small but significant accuracy in their impressions, with no other-race effect. Results are consistent with a degree of universality in the accuracy of this important aspect of social perception, provided that perceivers have experience with the faces being assessed.

Past visual experiences weigh in on body size estimation.

Body size is a salient marker of physical health, with extremes implicated in various mental and physical health issues. It is therefore important to understand the mechanisms of perception of body size of self and others. We report a novel technique we term the bodyline, based on the numberline technique in numerosity studies. One hundred and three young women judged the size of sequentially presented female body images by positioning a marker on a line, delineated with images of extreme sizes. Participants performed this task easily and well, with average standard deviations less than 6% of the total scale. Critically, judgments of size were biased towards the previously viewed body, demonstrating that serial dependencies occur in the judgment of body size. The magnitude of serial dependence was well predicted by a simple Kalman-filter ideal-observer model, suggesting that serial dependence occurs in an optimal, adaptive way to improve performance in size judgments.

Joint attention difficulties in autistic adults: An interactive eye-tracking study.

Joint attention - the ability to coordinate attention with a social partner - is critical for social communication, learning and the regulation of interpersonal relationships. Infants and young children with autism demonstrate impairments in both initiating and responding to joint attention bids in naturalistic settings. However, little is known about joint attention abilities in adults with autism. Here, we tested 17 autistic adults and 17 age- and nonverbal intelligence quotient-matched controls using an interactive eye-tracking paradigm in which participants initiated and responded to joint attention bids with an on-screen avatar. Compared to control participants, autistic adults completed fewer trials successfully. They were also slower to respond to joint attention bids in the first block of testing but performed as well as controls in the second block. There were no group differences in responding to spatial cues on a non-social task with similar attention and oculomotor demands. These experimental results were mirrored in the subjective reports given by participants, with some commenting that they initially found it challenging to communicate using eye gaze, but were able to develop strategies that allowed them to achieve joint attention. Our study indicates that for many autistic individuals, subtle difficulties using eye-gaze information persist well into adulthood.

A new other-race effect for gaze perception.

The well-known other-race effect in face recognition has been widely studied, both for its theoretical insights into the nature of face expertise and because of its social and forensic importance. Here we demonstrate an other-race effect for the perception of a simple visual signal provided by the eyes, namely gaze direction. In Study 1, Caucasian and Asian participants living in Australia both showed greater perceptual sensitivity to detect direct gaze in own-race than other-race faces. In Study 2, Asian (Chinese) participants living in Australia and Asian (Chinese) participants living in Hong Kong both showed this other-race effect, but Caucasian participants did not. Despite this inconsistency, meta-analysis revealed a significant other-race effect when results for all 5 participant groups from corresponding conditions in the 2 studies were combined. These results demonstrate a new other-race effect for the perception of the simple, but socially potent, cue of direct gaze. When identical morphed-race eyes were inserted into the faces, removing race-specific eye cues, no other-race effect was found (with 1 exception). Thus, the balance of evidence implicated perceptual expertise, rather than social motivation, in the other-race effect for detecting direct gaze. (PsycINFO Database Record

Watching the brain recalibrate: Neural correlates of renormalization during face adaptation.

The face perception system flexibly adjusts its neural responses to current face exposure, inducing aftereffects in the perception of subsequent faces. For instance, adaptation to expanded faces makes undistorted faces appear compressed, and adaptation to compressed faces makes undistorted faces appear expanded. Such distortion aftereffects have been proposed to result from renormalization, in which the visual system constantly updates a prototype according to the adaptors' characteristics and evaluates subsequent faces relative to that. However, although consequences of adaptation are easily observed in behavioral aftereffects, it has proven difficult to observe renormalization during adaptation itself. Here we directly measured brain responses during adaptation to establish a neural correlate of renormalization. Given that the face-evoked occipito-temporal P2 event-related brain potential has been found to increase with face prototypicality, we reasoned that the adaptor-elicited P2 could serve as an electrophysiological indicator for renormalization. Participants adapted to sequences of four distorted (compressed or expanded) or undistorted faces, followed by a slightly distorted test face, which they had to classify as undistorted or distorted. We analysed ERPs evoked by each of the adaptors and found that P2 (but not N170) amplitudes evoked by consecutive adaptor faces exhibited an electrophysiological pattern of renormalization during adaptation to distorted faces: P2 amplitudes evoked by both compressed and expanded adaptors significantly increased towards asymptotic levels as adaptation proceeded. P2 amplitudes were smallest for the first adaptor, significantly larger for the second, and yet larger for the third adaptor. We conclude that the sensitivity of the occipito-temporal P2 to the perceived deviation of a face from the norm makes this component an excellent tool to study adaptation-induced renormalization.

The contributions of temporal delay and face exposure to the decay of gaze direction aftereffects.

Gaze direction is a dynamic social signal that provides real-time insight into another person's focus of attention. Gaze adaptation induces aftereffects in the perception of gaze in subsequent faces, typically biasing it away from the adapted direction. Previous studies found that such gaze direction aftereffects persist for about 7 min when repeatedly tested immediately after adaptation, but can survive at least 24 hr when there is no testing immediately after adaptation. These findings suggest that exposure to test faces after adaptation might affect the persistence of gaze direction aftereffects more than the passing of time. The present study systematically established the contributions of time and intervening testing on the longevity of gaze direction aftereffects. Aftereffects were induced and then traced over six postadaptation tests. Participants were assigned to four groups with a delay of either 30 s, 3 min, 5.5 min, or 8 min between adaptation and the first postadaptation test. Aftereffects were strongly affected by the number of preceding postadaptation tests, but unaffected by the delay between adaptation and test, revealing that face exposure affects the longevity of aftereffects more strongly than the passing of time, at least over the time frame studied here. Our findings suggest that exposure to a substantial number of faces with an unbiased distribution of gaze directions may be necessary to overcome gaze direction aftereffects.

Gaze direction aftereffects are surprisingly long-lasting.

Adaptation to gaze direction induces aftereffects in the perception of gaze in subsequently presented faces. Gaze adaptation calibrates neural responses to the most frequently occurring gaze signals and therefore frees up capacity to respond to more novel signals, likely enhancing gaze discrimination and supporting novelty detection. The longevity of aftereffects can provide some insight into the temporal window over which this calibration occurs. Since gaze direction is a rapidly changing signal in the face, one might expect gaze aftereffects to also be very short-lived. Here we show that this is not the case. In Experiment 1, we measured participants' aftereffects immediately after gaze adaptation and 24 h later. We found significant aftereffects at both times. In Experiment 2, we tested whether long-term adaptation also occurred when aftereffects were measured only once, 24 h after adaptation. Again, we found significant long-term aftereffects. These results demonstrate that gaze adaptation can integrate information over remarkably long periods. We discuss the implications of the longevity of gaze direction aftereffects on our understanding of their functionality, and the functionality of face aftereffects more generally. (PsycINFO Database Record

Absence of Sex-Contingent Gaze Direction Aftereffects Suggests a Limit to Contingencies in Face Aftereffects.

Face aftereffects (e.g., expression aftereffects) can be simultaneously induced in opposite directions for different face categories (e.g., male and female faces). Such aftereffects are typically interpreted as indicating that distinct neural populations code the categories on which adaptation is contingent, e.g., male and female faces. Moreover, they suggest that these distinct populations selectively respond to variations in the secondary stimulus dimension, e.g., emotional expression. However, contingent aftereffects have now been reported for so many different combinations of face characteristics, that one might question this interpretation. Instead, the selectivity might be generated during the adaptation procedure, for instance as a result of associative learning, and not indicate pre-existing response selectivity in the face perception system. To alleviate this concern, one would need to demonstrate some limit to contingent aftereffects. Here, we report a clear limit, showing that gaze direction aftereffects are not contingent on face sex. We tested 36 young Caucasian adults in a gaze adaptation paradigm. We initially established their ability to discriminate the gaze direction of male and female test faces in a pre-adaptation phase. Afterwards, half of the participants adapted to female faces looking left and male faces looking right, and half adapted to the reverse pairing. We established the effects of this adaptation on the perception of gaze direction in subsequently presented male and female test faces. We found that adaptation induced pronounced gaze direction aftereffects, i.e., participants were biased to perceive small gaze deviations to both the left and right as direct. Importantly, however, aftereffects were identical for male and female test faces, showing that the contingency of face sex and gaze direction participants experienced during the adaptation procedure had no effect.

How Well Do Computer-Generated Faces Tap Face Expertise?

The use of computer-generated (CG) stimuli in face processing research is proliferating due to the ease with which faces can be generated, standardised and manipulated. However there has been surprisingly little research into whether CG faces are processed in the same way as photographs of real faces. The present study assessed how well CG faces tap face identity expertise by investigating whether two indicators of face expertise are reduced for CG faces when compared to face photographs. These indicators were accuracy for identification of own-race faces and the other-race effect (ORE)-the well-established finding that own-race faces are recognised more accurately than other-race faces. In Experiment 1 Caucasian and Asian participants completed a recognition memory task for own- and other-race real and CG faces. Overall accuracy for own-race faces was dramatically reduced for CG compared to real faces and the ORE was significantly and substantially attenuated for CG faces. Experiment 2 investigated perceptual discrimination for own- and other-race real and CG faces with Caucasian and Asian participants. Here again, accuracy for own-race faces was significantly reduced for CG compared to real faces. However the ORE was not affected by format. Together these results signal that CG faces of the type tested here do not fully tap face expertise. Technological advancement may, in the future, produce CG faces that are equivalent to real photographs. Until then caution is advised when interpreting results obtained using CG faces.

How distinct is the coding of face identity and expression? Evidence for some common dimensions in face space.

Traditional models of face perception emphasize distinct routes for processing face identity and expression. These models have been highly influential in guiding neural and behavioural research on the mechanisms of face perception. However, it is becoming clear that specialised brain areas for coding identity and expression may respond to both attributes and that identity and expression perception can interact. Here we use perceptual aftereffects to demonstrate the existence of dimensions in perceptual face space that code both identity and expression, further challenging the traditional view. Specifically, we find a significant positive association between face identity aftereffects and expression aftereffects, which dissociates from other face (gaze) and non-face (tilt) aftereffects. Importantly, individual variation in the adaptive calibration of these common dimensions significantly predicts ability to recognize both identity and expression. These results highlight the role of common dimensions in our ability to recognize identity and expression, and show why the high-level visual processing of these attributes is not entirely distinct.

Aging affects sex categorization of male and female faces in opposite ways.

Faces are rich in social information; they easily give away a person's sex, approximate age, feelings, or focus of attention. Past research has mostly focused on investigating the distinct facial signals and perceptual mechanisms that allow us to categorize faces on these individual dimensions. It is less well understood how the different kinds of facial information interact. Here we investigated how the age of a face affects the ease with which young and older adults categorize its sex. Disconfirming everyday intuition, we showed that sex categorization is not generally hampered for older faces. Although categorization of female faces took progressively more time with increasing age, the opposite was found for male faces (Experiment 1). Differential effects of stimulus blurring and inversion for male and female faces of different ages (Experiment 2) strongly suggest one feature as a crucial mediator of the interdependence of age and sex perception - skin texture.

Gaze direction affects the magnitude of face identity aftereffects.

The face perception system partly owes its efficiency to adaptive mechanisms that constantly recalibrate face coding to our current diet of faces. Moreover, faces that are better attended produce more adaptation. Here, we investigated whether the social cues conveyed by a face can influence the amount of adaptation that face induces. We compared the magnitude of face identity aftereffects induced by adaptors with direct and averted gazes. We reasoned that faces conveying direct gaze may be more engaging and better attended and thus produce larger aftereffects than those with averted gaze. Using an adaptation duration of 5 s, we found that aftereffects for adaptors with direct and averted gazes did not differ (Experiment 1). However, when processing demands were increased by reducing adaptation duration to 1 s, we found that gaze direction did affect the magnitude of the aftereffect, but in an unexpected direction: Aftereffects were larger for adaptors with averted rather than direct gaze (Experiment 2). Eye tracking revealed that differences in looking time to the faces between the two gaze directions could not account for these findings. Subsequent ratings of the stimuli (Experiment 3) showed that adaptors with averted gaze were actually perceived as more expressive and interesting than adaptors with direct gaze. Therefore it appears that the averted-gaze faces were more engaging and better attended, leading to larger aftereffects. Overall, our results suggest that naturally occurring facial signals can modulate the adaptive impact a face exerts on our perceptual system. Specifically, the faces that we perceive as most interesting also appear to calibrate the organization of our perceptual system most strongly.

On the other side of the fence: effects of social categorization and spatial grouping on memory and attention for own-race and other-race faces.

The term "own-race bias" refers to the phenomenon that humans are typically better at recognizing faces from their own than a different race. The perceptual expertise account assumes that our face perception system has adapted to the faces we are typically exposed to, equipping it poorly for the processing of other-race faces. Sociocognitive theories assume that other-race faces are initially categorized as out-group, decreasing motivation to individuate them. Supporting sociocognitive accounts, a recent study has reported improved recognition for other-race faces when these were categorized as belonging to the participants' in-group on a second social dimension, i.e., their university affiliation. Faces were studied in groups, containing both own-race and other-race faces, half of each labeled as in-group and out-group, respectively. When study faces were spatially grouped by race, participants showed a clear own-race bias. When faces were grouped by university affiliation, recognition of other-race faces from the social in-group was indistinguishable from own-race face recognition. The present study aimed at extending this singular finding to other races of faces and participants. Forty Asian and 40 European Australian participants studied Asian and European faces for a recognition test. Faces were presented in groups, containing an equal number of own-university and other-university Asian and European faces. Between participants, faces were grouped either according to race or university affiliation. Eye tracking was used to study the distribution of spatial attention to individual faces in the display. The race of the study faces significantly affected participants' memory, with better recognition of own-race than other-race faces. However, memory was unaffected by the university affiliation of the faces and by the criterion for their spatial grouping on the display. Eye tracking revealed strong looking biases towards both own-race and own-university faces. Results are discussed in light of the theoretical accounts of the own-race bias.

Aftereffects support opponent coding of face gender.

Many aspects of faces derived from structural information appear to be neurally represented using norm-based opponent coding. Recently, however, Zhao, Seriès, Hancock, and Bednar (2011) have argued that another aspect with a strong structural component, namely face gender, is instead multichannel coded. Their conclusion was based on finding that face gender aftereffects initially increased but then decreased for adaptors with increasing levels of gender caricaturing. Critically, this interpretation rests on the untested assumption that caricaturing the differences between male and female composite faces increases perceived sexual dimorphism (masculinity/femininity) of faces. We tested this assumption in Study 1 and found that it held for male, but not female faces. A multichannel account cannot, therefore, be ruled out, although a decrease in realism of adaptors was observed that could have contributed to the decrease in aftereffects. However, their aftereffects likely reflect low-level retinotopic adaptation, which was not minimized for most of their participants. In Study 2 we minimized low-level adaptation and found that face gender aftereffects were strongly positively related to the perceived sexual dimorphism of adaptors. We found no decrease for extreme adaptors, despite testing adaptors with higher perceived sexual dimorphism levels than those used by Zhao et al. These results are consistent with opponent coding of higher-level dimensions related to the perception of face gender.

Adaptation effects to attractiveness of face photographs and art portraits are domain-specific.

We studied the neural coding of facial attractiveness by investigating effects of adaptation to attractive and unattractive human faces on the perceived attractiveness of veridical human face pictures (Experiment 1) and art portraits (Experiment 2). Experiment 1 revealed a clear pattern of contrastive aftereffects. Relative to a pre-adaptation baseline, the perceived attractiveness of faces was increased after adaptation to unattractive faces, and was decreased after adaptation to attractive faces. Experiment 2 revealed similar aftereffects when art portraits rather than face photographs were used as adaptors and test stimuli, suggesting that effects of adaptation to attractiveness are not restricted to facial photographs. Additionally, we found similar aftereffects in art portraits for beauty, another aesthetic feature that, unlike attractiveness, relates to the properties of the image (rather than to the face displayed). Importantly, Experiment 3 showed that aftereffects were abolished when adaptors were art portraits and face photographs were test stimuli. These results suggest that adaptation to facial attractiveness elicits aftereffects in the perception of subsequently presented faces, for both face photographs and art portraits, and that these effects do not cross image domains.

Combined effects of inversion and feature removal on N170 responses elicited by faces and car fronts.

The face-sensitive N170 is typically enhanced for inverted compared to upright faces. Itier, Alain, Sedore, and McIntosh (2007) recently suggested that this N170 inversion effect is mainly driven by the eye region which becomes salient when the face configuration is disrupted. Here we tested whether similar effects could be observed with non-face objects that are structurally similar to faces in terms of possessing a homogeneous within-class first-order feature configuration. We presented upright and inverted pictures of intact car fronts, car fronts without lights, and isolated lights, in addition to analogous face conditions. Upright cars elicited substantial N170 responses of similar amplitude to those evoked by upright faces. In strong contrast to face conditions however, the car-elicited N170 was mainly driven by the global shape rather than the presence or absence of lights, and was dramatically reduced for isolated lights. Overall, our data confirm a differential influence of the eye region in upright and inverted faces. Results for car fronts do not suggest similar interactive encoding of eye-like features and configuration for non-face objects, even when these objects possess a similar feature configuration as faces.

Perceiving age and gender in unfamiliar faces: an fMRI study on face categorization.

Efficient processing of unfamiliar faces typically involves their categorization (e.g., into old vs. young or male vs. female). However, age and gender categorization may pose different perceptual demands. In the present study, we employed functional magnetic resonance imaging (fMRI) to compare the activity evoked during age vs. gender categorization of unfamiliar faces. In different blocks, participants performed age and gender classifications for old or young unfamiliar faces (50% female respectively). Both tasks elicited activations in the bilateral fusiform gyri (fusiform face area, FFA) and bilateral inferior occipital gyri (occipital face area, OFA). Importantly, the same stimuli elicited enhanced activation during gender as compared to age categorization. This enhancement was significant in the right FFA and the left OFA, and may be related to increased configural processing. Our findings replicate and extend recent work, and shows that the activation of core components of the face processing network is strongly dependent on task demands.

Facial attractiveness biases the perception of eye contact.

Attractive faces are appealing: We like to look at them, and we like to be looked at by them. We presented attractive and unattractive smiling and neutral faces containing identical eye regions with different gaze directions. Participants judged whether or not a face looked directly at them. Overall, attractive faces increased participants' tendency to perceive eye contact, consistent with a self-referential positivity bias. However, attractiveness effects were modulated by facial expression and gender: For female faces, observers more likely perceived eye contact in attractive than unattractive faces, independent of expression. For male faces, attractiveness effects were limited to neutral expressions and were absent in smiling faces. A signal detection analysis elucidated a systematic pattern in which (a) smiling faces, but not highly attractive faces, reduced sensitivity in gaze perception overall, and (b) attractiveness had a more consistent impact on bias than sensitivity measures. We conclude that combined influences of attractiveness, expression, and gender determine the formation of an overall impression when deciding which individual's interest in oneself may be beneficial and should be reciprocated.