Autistic adults exhibit typical sensitivity to changes in interpersonal distance.

The visual processing differences seen in autism often impede individuals' visual perception of the social world. In particular, many autistic people exhibit poor face recognition. Here, we sought to determine whether autistic adults also show impaired perception of dyadic social interactions-a class of stimulus thought to engage face-like visual processing. Our focus was the perception of interpersonal distance. Participants completed distance change detection tasks, in which they had to make perceptual decisions about the distance between two actors. On half of the trials, participants judged whether the actors moved closer together; on the other half, whether they moved further apart. In a nonsocial control task, participants made similar judgments about two grandfather clocks. We also assessed participants' face recognition ability using standardized measures. The autistic and nonautistic observers showed similar levels of perceptual sensitivity to changes in interpersonal distance when viewing social interactions. As expected, however, the autistic observers showed clear signs of impaired face recognition. Despite putative similarities between the visual processing of faces and dyadic social interactions, our results suggest that these two facets of social vision may dissociate.

Face masks and fake masks: the effect of real and superimposed masks on face matching with super-recognisers, typical observers, and algorithms.

Mask wearing has been required in various settings since the outbreak of COVID-19, and research has shown that identity judgements are difficult for faces wearing masks. To date, however, the majority of experiments on face identification with masked faces tested humans and computer algorithms using images with superimposed masks rather than images of people wearing real face coverings. In three experiments we test humans (control participants and super-recognisers) and algorithms with images showing different types of face coverings. In all experiments we tested matching concealed or unconcealed faces to an unconcealed reference image, and we found a consistent decrease in face matching accuracy with masked compared to unconcealed faces. In Experiment 1, typical human observers were most accurate at face matching with unconcealed images, and poorer for three different types of superimposed mask conditions. In Experiment 2, we tested both typical observers and super-recognisers with superimposed and real face masks, and found that performance was poorer for real compared to superimposed masks. The same pattern was observed in Experiment 3 with algorithms. Our results highlight the importance of testing both humans and algorithms with real face masks, as using only superimposed masks may underestimate their detrimental effect on face identification.

New evidence of impaired expression recognition in developmental prosopagnosia.

Developmental prosopagnosia (DP) is a neurodevelopmental condition characterized by lifelong face recognition difficulties. To date, it remains unclear whether or not individuals with DP experience impaired recognition of facial expressions. It has been proposed that DPs may have sufficient perceptual ability to correctly interpret facial expressions when tasks are relatively easy (e.g., the stimuli are unambiguous and viewing conditions are optimal), but exhibit subtle impairments when tested under more challenging conditions. In the present study, we sought to take advantage of the COVID-19 pandemic to test this view. It is well-established that the surgical-type masks worn during the pandemic hinder the recognition and interpretation of facial emotion in typical participants. Relative to typical participants, we hypothesized that DPs may be disproportionately impaired when asked to interpret the facial emotion of people wearing face masks. We compared the ability of 34 DPs and 60 age-matched typical controls to recognize facial emotions i) when the whole face is visible, and ii) when the lower portion of the face is covered with a surgical mask. When expression stimuli were viewed without a mask, the DPs and typical controls exhibited similar levels of performance. However, when expression stimuli were shown with a mask, the DPs showed signs of subtle expression recognition deficits. The DPs were particularly prone to mislabeling masked expressions of happiness as emotion neutral. These results add to a growing body of evidence that under some conditions, DPs do exhibit subtle deficits of expression recognition.

Impaired grouping of ambient facial images in autism.

Ambient facial images depict individuals from a variety of viewing angles, with a range of poses and expressions, under different lighting conditions. Exposure to ambient images is thought to help observers form robust representations of the individuals depicted. Previous results suggest that autistic people may derive less benefit from exposure to this exemplar variation than non-autistic people. To date, however, it remains unclear why. One possibility is that autistic individuals possess atypical perceptual learning mechanisms. Alternatively, however, the learning mechanisms may be intact, but receive low-quality perceptual input from face encoding processes. To examine this second possibility, we investigated whether autistic people are less able to group ambient images of unfamiliar individuals based on their identity. Participants were asked to identify which of four ambient images depicted an oddball identity. Each trial assessed the grouping of different facial identities, thereby preventing face learning across trials. As such, the task assessed participants' ability to group ambient images of unfamiliar people. In two experiments we found that matched non-autistic controls correctly identified the oddball identities more often than our autistic participants. These results imply that poor face learning from variation by autistic individuals may well be attributable to low-quality perceptual input, not aberrant learning mechanisms.

Sensitivity to orientation is not unique to social attention cueing.

It is well-established that faces and bodies cue observers' visuospatial attention; for example, target items are found faster when their location is cued by the directionality of a task-irrelevant face or body. Previous results suggest that these cueing effects are greatly reduced when the orientation of the task-irrelevant stimulus is inverted. It remains unclear, however, whether sensitivity to orientation is a unique hallmark of "social" attention cueing or a more general phenomenon. In the present study, we sought to determine whether the cueing effects produced by common objects (power drills, desk lamps, desk fans, cameras, bicycles, and cars) are also attenuated by inversion. When cueing stimuli were shown upright, all six object classes produced highly significant cueing effects. When shown upside-down, however, the results were mixed. Some of the cueing effects (e.g., those induced by bicycles and cameras) behaved liked faces and bodies: they were greatly reduced by orientation inversion. However, other cueing effects (e.g., those induced by cars and power drills) were insensitive to orientation: upright and inverted exemplars produced significant cueing effects of comparable strength. We speculate that (i) cueing effects depend on the rapid identification of stimulus directionality, and (ii) some cueing effects are sensitive to orientation because upright exemplars of those categories afford faster processing of directionality, than inverted exemplars. Contrary to the view that attenuation-by-inversion is a unique hallmark of social attention, our findings indicate that some non-social cueing effects also exhibit sensitivity to orientation.

How does the presence of a surgical face mask impair the perceived intensity of facial emotions?

The use of surgical-type face masks has become increasingly common during the COVID-19 pandemic. Recent findings suggest that it is harder to categorise the facial expressions of masked faces, than of unmasked faces. To date, studies of the effects of mask-wearing on emotion recognition have used categorisation paradigms: authors have presented facial expression stimuli and examined participants' ability to attach the correct label (e.g., happiness, disgust). While the ability to categorise particular expressions is important, this approach overlooks the fact that expression intensity is also informative during social interaction. For example, when predicting an interactant's future behaviour, it is useful to know whether they are slightly fearful or terrified, contented or very happy, slightly annoyed or angry. Moreover, because categorisation paradigms force observers to pick a single label to describe their percept, any additional dimensionality within observers' interpretation is lost. In the present study, we adopted a complementary emotion-intensity rating paradigm to study the effects of mask-wearing on expression interpretation. In an online experiment with 120 participants (82 female), we investigated how the presence of face masks affects the perceived emotional profile of prototypical expressions of happiness, sadness, anger, fear, disgust, and surprise. For each of these facial expressions, we measured the perceived intensity of all six emotions. We found that the perceived intensity of intended emotions (i.e., the emotion that the actor intended to convey) was reduced by the presence of a mask for all expressions except for anger. Additionally, when viewing all expressions except surprise, masks increased the perceived intensity of non-intended emotions (i.e., emotions that the actor did not intend to convey). Intensity ratings were unaffected by presentation duration (500ms vs 3000ms), or attitudes towards mask wearing. These findings shed light on the ambiguity that arises when interpreting the facial expressions of masked faces.

Objects that direct visuospatial attention produce the search advantage for facing dyads.

When hidden among pairs of individuals facing in the same direction, pairs of individuals arranged front-to-front are found faster in visual search tasks than pairs of individuals arranged back-to-back. Two rival explanations have been advanced to explain this search advantage for facing dyads. According to one account, the search advantage reflects the fact that front-to-front targets engage domain-specific social interaction processing that helps stimuli compete more effectively for limited attentional resources. Another view is that the effect is a by-product of the ability of individual heads and bodies to direct observers' visuospatial attention. Here, we describe a two-part investigation that sought to test these accounts. First, we found that it is possible to replicate the search advantage with nonsocial objects. Next, we employed a cuing paradigm to investigate whether it is the ability of individual items to direct observers' visuospatial attention that determines if an object category produces the search advantage for facing dyads. We found that the strength of the cuing effect produced by an object category correlated closely with the strength of the search advantage produced by that object category. Taken together, these results provide strong support for the directional cuing account. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The effect of face masks and sunglasses on identity and expression recognition with super-recognizers and typical observers.

Face masks present a new challenge to face identification (here matching) and emotion recognition in Western cultures. Here, we present the results of three experiments that test the effect of masks, and also the effect of sunglasses (an occlusion that individuals tend to have more experienced with) on (i) familiar face matching, (ii) unfamiliar face matching and (iii) emotion categorization. Occlusion reduced accuracy in all three tasks, with most errors in the mask condition; however, there was little difference in performance for faces in masks compared with faces in sunglasses. Super-recognizers, people who are highly skilled at matching unconcealed faces, were impaired by occlusion, but at the group level, performed with higher accuracy than controls on all tasks. Results inform psychology theory with implications for everyday interactions, security and policing in a mask-wearing society.

Searching for people: Non-facing distractor pairs hinder the visual search of social scenes more than facing distractor pairs.

There is growing interest in the visual and attentional processes recruited when human observers view social scenes containing multiple people. Findings from visual search paradigms have helped shape this emerging literature. Previous research has established that, when hidden amongst pairs of individuals facing in the same direction (leftwards or rightwards), pairs of individuals arranged front-to-front are found faster than pairs of individuals arranged back-to-back. Here, we describe a second, closely-related effect with important theoretical implications. When searching for a pair of individuals facing in the same direction (leftwards or rightwards), target dyads are found faster when hidden amongst distractor pairs arranged front-to-front, than when hidden amongst distractor pairs arranged back-to-back. This distractor arrangement effect was also obtained with target and distractor pairs constructed from arrows and types of common objects that cue visuospatial attention. These findings argue against the view that pairs of people arranged front-to-front capture exogenous attention due to a domain-specific orienting mechanism. Rather, it appears that salient direction cues (e.g., gaze direction, body orientation, arrows) hamper systematic search and impede efficient interpretation, when distractor pairs are arranged back-to-back.

The perception of interpersonal distance is distorted by the Müller-Lyer illusion.

There is growing interest in how human observers perceive social scenes containing multiple people. Interpersonal distance is a critical feature when appraising these scenes; proxemic cues are used by observers to infer whether two people are interacting, the nature of their relationship, and the valence of their current interaction. Presently, however, remarkably little is known about how interpersonal distance is encoded within the human visual system. Here we show that the perception of interpersonal distance is distorted by the Müller-Lyer illusion. Participants perceived the distance between two target points to be compressed or expanded depending on whether face pairs were positioned inside or outside the to-be-judged interval. This illusory bias was found to be unaffected by manipulations of face direction. These findings aid our understanding of how human observers perceive interpersonal distance and may inform theoretical accounts of the Müller-Lyer illusion.

Visual search for facing and non-facing people: The effect of actor inversion.

In recent years, there has been growing interest in how human observers perceive, attend to, and recall, social interactions viewed from third-person perspectives. One of the interesting findings to emerge from this new literature is the search advantage for facing dyads. When hidden amongst pairs of individuals facing in the same direction, pairs of individuals arranged front-to-front are found faster in visual search tasks than pairs of individuals arranged back-to-back. Interestingly, the search advantage for facing dyads appears to be sensitive to the orientation of the people depicted. While front-to-front target pairs are found faster than back-to-back targets when target and distractor pairings are shown upright, front-to-front and back-to-back targets are found equally quickly when pairings are shown upside-down. In the present study, we sought to better understand why the search advantage for facing dyads is sensitive to the orientation of the people depicted. To begin, we show that the orientation sensitivity of the search advantage is seen with dyads constructed from faces only, and from bodies with the head and face occluded. We replicate these effects using two different visual search paradigms. We go on to show that individual faces and bodies, viewed in profile, produce strong attentional cueing effects when shown upright, but not when presented upside-down. Together with recent evidence that arrows arranged front-to-front also produce the search advantage for facing dyads, these findings support the view that the search advantage is a by-product of the ability of constituent elements to direct observers' visuo-spatial attention.

Holistic processing of facial identity in developmental prosopagnosia.

The nature of the perceptual deficit seen in developmental prosopagnosia remains poorly understood. One possibility is that these individuals experience face recognition difficulties because they fail to process faces holistically; they may be less able to analyze distal regions in parallel and therefore struggle to integrate information from different regions into a unified perceptual whole. Consequently, developmental prosopagnosics may be forced to base perceptual decisions on a slow, effortful piecemeal analysis of local facial features. In the present study, we sought to test this view by comparing the face recognition of developmental prosopagnosics and typical observers under two viewing conditions: when target faces were briefly presented in their entirety, and when they were inspected region-by-region through a dynamic aperture. If developmental prosopagnosics are forced to base perceptual decisions on information accumulated from a serial piecemeal analysis, one would expect little if any decrement in performance when target faces are viewed through apertures. Contrary to this prediction, however, developmental prosopagnosics showed strong aperture effects comparable with typical observers; their perceptual decisions were more accurate in the whole-face condition than when targets were viewed through the aperture. As expected, the developmental prosopagnosics were less accurate than typical controls when judging briefly presented faces shown in their entirety. Strikingly, however, they were also less able to accumulate perceptual evidence from a serial region-by-region analysis, than typical observers. Our results suggest that the perceptual problems seen in this population arise from imprecise descriptions of local regions, not aberrant holistic processing.

Why are social interactions found quickly in visual search tasks?

When asked to find a target dyad amongst non-interacting individuals, participants respond faster when the individuals in the target dyad are shown face-to-face (suggestive of a social interaction), than when they are presented back-to-back. Face-to-face dyads may be found faster because social interactions recruit specialized processing. However, human faces and bodies are salient directional cues that exert a strong influence on how observers distribute their attention. Here we report that a similar search advantage exists for 'point-to-point' and 'point-to-face' target arrangements constructed using arrows - a non-social directional cue. These findings indicate that the search advantage seen for face-to-face dyads is a product of the directional cues present within arrangements, not the fact that they are processed as social interactions, per se. One possibility is that, when arranged in the face-to-face or point-to-point configuration, pairs of directional cues (faces, bodies, arrows) create an attentional 'hot-spot' - a region of space in between the elements to which attention is directed by multiple cues. Due to the presence of this hot-spot, observers' attention may be drawn to the target location earlier in a serial visual search.

Nonlinear transduction of emotional facial expression.

To create neural representations of external stimuli, the brain performs a number of processing steps that transform its inputs. For fundamental attributes, such as stimulus contrast, this involves one or more nonlinearities that are believed to optimise the neural code to represent features of the natural environment. Here we ask if the same is also true of more complex stimulus dimensions, such as emotional facial expression. We report the results of three experiments combining morphed facial stimuli with electrophysiological and psychophysical methods to measure the function mapping emotional expression intensity to internal response. The results converge on a nonlinearity that accelerates over weak expressions, and then becomes shallower for stronger expressions, similar to the situation for lower level stimulus properties. We further demonstrate that the nonlinearity is not attributable to the morphing procedure used in stimulus generation.

Inverted faces benefit from whole-face processing.

Upright faces are thought to engage holistic processing whereby local regions are integrated into a unified whole for the purposes of rapid, efficient analysis. In contrast, inverted faces are thought to recruit a slower, less-accurate serial analysis of local features. Aperture paradigms, whereby a target face is revealed by a dynamic viewing window that shifts over the stimulus image, offer a compelling test of this view. If upright faces are processed holistically, perceptual judgements ought to be substantially disrupted when stimuli are viewed through apertures. In contrast, aperture viewing should produce little or no decrement in perceptual decisions when judging inverted faces, as they are thought to be subjected to serial feature-based analysis. Here we present four experiments that elucidate the effects of aperture viewing on the perception of upright and inverted faces. In our first two experiments, we find evidence of disproportionate aperture effects for upright faces relative to inverted faces. However, these findings are qualified by the fact that observers found it harder to discriminate inverted faces presented in the 'baseline' whole-face condition. When observers' ability to discriminate faces in the whole-face condition was matched for difficulty (Experiments 3 and 4), we show that upright and inverted faces produce very similar aperture effects. These findings indicate that both upright and inverted faces benefit from whole-face processing and accord with other lines of evidence that faces engage qualitatively similar types of processing in both orientations.

Are the facial gender and facial age variants of the composite face illusion products of a common mechanism?

When the upper half of one face ('target region') is spatially aligned with the lower half of another ('distractor region'), the two halves appear to fuse together perceptually, changing observers' subjective perception of the target region. This 'composite face illusion' is regarded as a key hallmark of holistic face processing. Importantly, distractor regions bias observers' subjective perception of target regions in systematic, predictable ways. For example, male and female distractor regions make target regions appear masculine and feminine; young and old distractor regions make target regions appear younger and older. In the present study, we first describe a novel psychophysical paradigm that yields precise reliable estimates of these perceptual biases. Next, we use this novel procedure to establish a clear relationship between observers' susceptibility to the age and gender biases induced by the composite face illusion. This relationship is seen in a lab-based sample (N = 100) and is replicated in an independent sample tested online (N = 121). Our findings suggest that age and gender variants of the composite illusion may be different measures of a common structural binding process, with an origin early in the face-processing stream.

The discrimination of facial sex in developmental prosopagnosia.

Developmental prosopagnosia (DP) is a neurodevelopmental condition characterised by difficulties recognising and discriminating faces. It is currently unclear whether the perceptual impairments seen in DP are restricted to identity information, or also affect the perception of other facial characteristics. To address this question, we compared the performance of 17 DPs and matched controls on two sensitive sex categorisation tasks. First, in a morph categorisation task, participants made binary decisions about faces drawn from a morph continuum that blended incrementally an average male face and an average female face. We found that judgement precision was significantly lower in the DPs than in the typical controls. Second, we used a sex discrimination task, where female or male facial identities were blended with an androgynous average face. We manipulated the relative weighting of each facial identity and the androgynous average to create four levels of signal strength. We found that DPs were significantly less sensitive than controls at each level of difficulty. Together, these results suggest that the visual processing difficulties in DP extend beyond the extraction of facial identity and affects the extraction of other facial characteristics. Deficits of facial sex categorisation accord with an apperceptive characterisation of DP.

Face perception in autism spectrum disorder: Modulation of holistic processing by facial emotion.

Individuals with Autism Spectrum Disorder (ASD; autistic individuals) may exhibit atypical face perception because they fail to process faces holistically. In the context of this hypothesis, it is critical to determine whether autistic individuals exhibit diminished susceptibility to the composite face illusion, widely regarded as a key marker of holistic face processing. To date, however, previous studies have yielded inconsistent findings. In light of recent evidence suggesting that facial emotion cues increase the strength of the composite face illusion in typical individuals, the present study sought to determine whether the presence of facial emotion also modulates the strength of the composite face illusion in autistic individuals, many of whom experience difficulties recognizing facial expressions. We therefore measured composite face effects in a sample of autistic individuals (N = 20) and matched typical controls (N = 29) using an incidental emotion procedure in which distractor regions varied systematically in their emotion strength. As expected, the presence of facial emotion in the distractor regions of composite face arrangements increased the strength of the illusory distortion induced. The extent of the modulation by facial emotion was similar in the two groups. The composite effects seen in the ASD group were qualitatively and quantitatively similar to those seen in the typical group, suggestive of intact holistic processing in this population.

Does developmental prosopagnosia impair identification of other-ethnicity faces?

Current approaches to the diagnosis of developmental prosopagnosia emphasise the perception and identification of same-ethnicity faces. This convention ensures that perceptual impairment arising from developmental prosopagnosia can be distinguished from problems arising from a lack of visual experience with particular facial ethnicities - the so-called 'Other-Ethnicity Effect'. The present study sought to determine whether the perceptual difficulties seen in developmental prosopagnosia - diagnosed using same-ethnicity faces - extend to other-ethnicity faces. First, we sought to determine whether a group of Caucasian developmental prosopagnosics (N = 15) and typical Caucasian controls (N = 30) had similar experience with same- and other-ethnicity faces during development. All participants therefore completed a contact questionnaire that enquired about their experience of Caucasian, Black, and East Asian faces, at different developmental stages. Importantly, the two groups described very similar levels of visual experience with other-ethnicity faces. Second, we administered a sequential matching task to measure participants' ability to discriminate same- (Caucasian) and other-ethnicity (Black, East Asian) faces. Relative to the experience-matched controls, the prosopagnosics were less accurate at discriminating both same- and other-ethnicity faces, and we found no evidence of disproportionate impairment for same-ethnicity faces. Given that the prosopagnosics and controls had similar opportunity to develop visual expertise for other-ethnicity faces, these results indicate that developmental prosopagnosia impairs recognition of both same- and other-ethnicity faces. The fact that developmental prosopagnosia affects the perception of both same- and other-ethnicity faces suggests that different facial ethnicities engage similar visual processing mechanisms. Our findings support the view that susceptibility to developmental prosopagnosia, and a lack of contact with other-ethnicity faces, contribute independently to the poor recognition of other-ethnicity faces.

Evaluating object recognition ability in developmental prosopagnosia using the Cambridge Car Memory Test.

Individuals with developmental prosopagnosia (DP) sometimes experience object identification difficulties in addition to problems recognizing faces. To better understand the distribution of non-face object recognition ability in this population, we administered the Cambridge Car Memory Test (CCMT) - a leading, standardized measure of object recognition ability - to a large sample of DPs (N = 46). When considered as a single group, the DPs scored lower than matched controls. This finding provides further evidence that developmental object agnosia (DOA) may be more common in DP than in the general population. Relative to the DPs' face recognition deficits, however, car matching deficits were small and inconsistent. In fact, we observed a striking range of CCMT performance in our DP sample. While some DPs performed extremely poorly, many more achieved scores within one standard deviation of the typical mean, and several DP participants achieved excellent CCMT scores comparable with the best controls.