Categorical perception of race

Registered report "Categorical perception of facial expressions of anger and disgust across cultures"

Previous research has demonstrated that individuals from Western cultures exhibit categorical perception (CP) in their judgments of emotional faces. However, the extent to which this phenomenon characterises the judgments of facial expressions among East Asians remains relatively unexplored. Building upon recent findings showing that East Asians are more likely than Westerners to see a mixture of emotions in facial expressions of anger and disgust, the present research aimed to investigate whether East Asians also display CP for angry and disgusted faces. To address this question, participants from Canada and China were recruited to discriminate pairs of faces along the anger-disgust continuum. The results revealed the presence of CP in both cultural groups, as participants consistently exhibited higher accuracy and faster response latencies when discriminating between-category pairs of expressions compared to within-category pairs. Moreover, the magnitude of CP did not vary significantly across cultures. These findings provide novel evidence supporting the existence of CP for facial expressions in both East Asian and Western cultures, suggesting that CP is a perceptual phenomenon that transcends cultural boundaries. This research contributes to the growing literature on cross-cultural perceptions of facial expressions by deepening our understanding of how facial expressions are perceived categorically across cultures.

Bias in perceptual learning

Perceptual learning is commonly understood as conferring some benefit to the learner, such as allowing for the extraction of more information from the environment. However, perceptual learning can be biased in several different ways, some of which do not appear to provide such a benefit. Here we outline a systematic framework for thinking about bias in perceptual learning and discuss how several cases fit into this framework. We argue these biases are compatible with an understanding in which perceptual learning is beneficial, but that its benefits are tied to both a person's narrow interests and the training environment or domain, and so if there are changes to either of these, then benefits can turn into liabilities, though these are often temporary. This article is categorized under: Psychology > Learning Philosophy > Value Linguistics > Language Acquisition.

Examining the Contribution of Physical Cues for Same- and Cross-Race Face Individuation

Face individuation involves sensitivity to physical characteristics that provide information about identity. We examined whether Black and White American faces differ in terms of individuating information, and whether Black and White perceivers differentially weight information when judging same-race and cross-race faces. Study 1 analyzed 20 structural metrics (e.g., eye width, nose length) of 158 Black and White faces to determine which differentiate faces within each group. High-utility metrics (e.g., nose length, eye height, chin length) differentiated faces of both groups, low-utility metrics (e.g., face width, eye width, face length) offered less individuating information. Study 2 (N = 4,510) explored Black and White participants' sensitivity to variation on structural metrics using similarity ratings. High-utility metrics affected perceived dissimilarity more than low-utility metrics. This relationship was non-significantly stronger for same-race faces rather than cross-race faces. Perceivers also relied more on features that were racially stereotypic of the faces they were rating.

Influence of Economic Scarcity on Race Perception

Racial socioeconomic gaps are widened in periods of economic recession. Besides social and institutional factors, black people also struggle with many psychological factors. The literature reports racial-biased complex behaviors and high-level processes that are influenced by economic scarcity. A previous study found a bias at the perceptual level: an experimental manipulation of scarcity (a subliminal priming paradigm) lowered the black-white race categorization threshold. Here we present a conceptual replication in a higher ecological setup. In our main analysis we compared the categorization threshold of participants that received the Brazilian government's emergency economic aid in the context of the COVID-19 pandemic (n = 136) and participants that did not receive the economic aid (n = 135) in an online psychophysical task that presented faces in a black-white race continuum. Additionally, we analyzed the economic impact of COVID-19 on household income, and in cases of family unemployment. Our results do not support the claim that perception of race is influenced by economic scarcity. Interestingly, we found that when people differ greatly in terms of racial prejudice, they encode visual information related to race differently. People with higher scores on a prejudice scale needed more phenotypic traits of the black race to categorize a face as black. We discuss the results in terms of differences in method and sample.

Face templates for the Chicago Face Database

Researchers often need to manipulate faces, such as developing a continuum between two faces or averaging a set of faces. In order to do so, researchers use morphing software, but they first need to fit a template to the idiosyncratic landmarks in each face. In this paper, we present a set of landmark templates for the Chicago Face Database (CFD; Ma, D. S., Correll, J., & Wittenbrink, B. (2015). The Chicago Face Database: A free stimulus set of faces and norming data. Behavior Research Methods, 47(4), 1122-1135). The CFD is a free online face database containing images of faces of people from various races and genders. We provide templates for each of 597 neutral (non-expressive) faces in version two of the CFD. Our templates are unique because the facial landmarks were hand placed by researchers. Hand placing facial landmarks allows for more accurate placement of landmarks than a computer-generated template. Historically, hand-placed templates were created by individual labs and not shared. In this paper, we describe how our templates were created, and some possible uses for the templates. We hope that our templates ease the burden for other researchers to manipulate faces.

Early detection of language categories in face perception

Does language categorization influence face identification? The present study addressed this question by means of two experiments. First, to establish language categorization of faces, the memory confusion paradigm was used to create two language categories of faces, Spanish and English. Subsequently, participants underwent an oddball paradigm, in which faces that had been previously paired with one of the two languages (Spanish or English), were presented. We measured EEG perceptual differences (vMMN) between standard and two types of deviant faces: within-language category (faces sharing language with standards) or between-language category (faces paired with the other language). Participants were more likely to confuse faces within the language category than between categories, an index that faces were categorized by language. At the neural level, early vMMN were obtained for between-language category faces, but not for within-language category faces. At a later stage, however, larger vMMNs were obtained for those faces from the same language category. Our results showed that language is a relevant social cue that individuals used to categorize others and this categorization subsequently affects face perception.

Behavioural mimicry as an indicator of affiliation

Previous research has shown that behavioural mimicry fosters affiliation, and can be used to infer whether people belong to the same social unit. However, we still know very little about the generalizability of these findings and the individual factors involved. The present study intends to disentangle two important variables and assess their importance for affiliation: the matching in time of the behaviours versus their matching in form. In order to address this issue, we presented participants with short videos in which two actors displayed a set of small movements (e.g. crossing their legs, folding their arms, tapping their fingers) arranged to be either contingent in time or in form. A dark filter was used to eliminate ostensive group marks, such us phenotype or clothing. Participants attributed the highest degree of affiliation to the actors when their subsequent movements matched in form, but were delayed by 4–5 seconds, and the lowest degree when the timing of their movements matched, but they differed in form. To assess the generalizability of our findings, we took our study outside the usual Western context and tested a matching sample of participants from a traditional small-scale society in Kenya. In all, our results suggest that movements are used to judge the degree of affiliation between two individuals in both large- and small-scale societies. While moving in different ways at the same time seems to increase the perceived distance between two individuals, movements which match in form seem to invoke closeness.

Perceived similarity ratings predict generalization success after traditional category learning and a new paired-associate learning task

The current study investigated category learning across two experiments using face-blend stimuli that formed face families controlled for within- and between-category similarity. Experiment 1 was a traditional feedback-based category-learning task, with three family names serving as category labels. In Experiment 2, the shared family name was encountered in the context of a face-full name paired-associate learning task, with a unique first name for each face. A subsequent test that required participants to categorize new faces from each family showed successful generalization in both experiments. Furthermore, perceived similarity ratings for pairs of faces were collected before and after learning, prior to generalization test. In Experiment 1, similarity ratings increased for faces within a family and decreased for faces that were physically similar but belonged to different families. In Experiment 2, overall similarity ratings decreased after learning, driven primarily by decreases for physically similar faces from different families. The post-learning category bias in similarity ratings was predictive of subsequent generalization success in both experiments. The results indicate that individuals formed generalizable category knowledge prior to an explicit demand to generalize and did so both when attention was directed towards category-relevant features (Experiment 1) and when attention was directed towards individuating faces within a family (Experiment 2). The results tie together research on category learning and categorical perception and extend them beyond a traditional category-learning task.

Exposure to linguistic labels during childhood modulates the neural architecture of race categorical perception

Perceptually categorizing a face to its racial belonging may have important consequences on interacting with people. However, race categorical perception (CP) has been scarcely investigated nor its developmental pathway. In this study, we tested the neurolinguistics rewiring hypothesis, stating that language acquisition modulates the brain processing of social perceptual categories. Accordingly, we investigated the electrophysiological correlates of race CP in a group of adults and children between 3 and 5 years of age. For both groups we found a greater modulation of the N400 connected with the processing of between category boundaries (i.e., faces belonging to different race groups) than within-category boundaries (i.e., different faces belonging to the same race group). This effect was the same in both adults and children, as shown by the comparable between-group amplitude of the differential wave (DW) elicited by the between-category faces. Remarkably, this effect was positively correlated with racial-labels acquisition, but not with age, in children. Finally, brain source analysis revealed the activation of a more modularized cortical network in adults than in children, with unique activation of the left superior temporal gyrus (STG) and the inferior frontal gyrus (IFG), which are areas connected to language processing. These are the first results accounting for an effect of language in rewiring brain connectedness when processing racial categories.

Those Virtual People all Look the Same to me: Computer-Rendered Faces Elicit a Higher False Alarm Rate Than Real Human Faces in a Recognition Memory Task

Virtual as compared with real human characters can elicit a sense of uneasiness in human observers, characterized by lack of familiarity and even feelings of eeriness (the “uncanny valley” hypothesis). Here we test the possibility that this alleged lack of familiarity is literal in the sense that people have lesser perceptual expertise in processing virtual as compared with real human faces. Sixty-four participants took part in a recognition memory study in which they first learned a set of faces and were then asked to recognize them in a testing session. We used real and virtual (computer-rendered) versions of the same faces, presented in either upright or inverted orientation. Real and virtual faces were matched for low-level visual features such as global luminosity and spatial frequency contents. Our results demonstrated a higher response bias toward responding “seen before” for virtual as compared with real faces, which was further explained by a higher false alarm rate for the former. This finding resembles a similar effect for recognizing human faces from other than one's own ethnic groups (the “other race effect”). Virtual faces received clearly higher subjective eeriness ratings than real faces. Our results did not provide evidence of poorer overall recognition memory or lesser inversion effect for virtual faces, however. The higher false alarm rate finding supports the notion that lesser perceptual expertise may contribute to the lack of subjective familiarity with virtual faces. We discuss alternative interpretations and provide suggestions for future research.

Newly learned categories induce pre-attentive categorical perception of faces

Face perception is modulated by categorical information in faces, which is known as categorical perception (CP) of faces. However, it remains unknown whether CP of faces is humans’ inborn capability or the result of acquired categories. Here, we examined whether and when newly learned categories affect face perception. A short-term training method was employed in which participants learned new categories of face stimuli. Behaviorally, using an AB-X discrimination task, we found that the discrimination accuracy of face pairs from different learned categories was significantly higher than that of faces from the same category. Neurally, using a visual oddball task, we found that deviant stimuli whose category differed from standard stimuli evoked a larger N170. Importantly, the visual mismatch negativity (vMMN), starting from 140 ms after stimuli onset, was stronger with the between-category deviants than with the within-category deviants under the unattended condition. Altogether, our study provides empirical evidence indicating that CP of faces could be induced by newly learned categories, and this effect occurs automatically during an early stage of processing.

Image Dependency in the Recognition of Newly Learnt Faces

Research investigating the effect of lighting and viewpoint changes on unfamiliar and newly learnt faces has revealed that such recognition is highly image dependent and that changes in either of these leads to poor recognition accuracy. Three experiments are reported to extend these findings by examining the effect of apparent age on the recognition of newly learnt faces. Experiment 1 investigated the ability to generalize to novel ages of a face after learning a single image. It was found that recognition was best for the learnt image with performance falling the greater the dissimilarity between the study and test images. Experiments 2 and 3 examined whether learning two images aids subsequent recognition of a novel image. The results indicated that interpolation between two studied images (Experiment 2) provided some additional benefit over learning a single view, but that this did not extend to extrapolation (Experiment 3). The results from all studies suggest that recognition was driven primarily by pictorial codes and that the recognition of faces learnt from a limited number of sources operates on stored images of faces as opposed to more abstract, structural, representations.

Of Kith and Kin: Perceptual Enrichment, Expectancy, and Reciprocity in Face Perception

Race powerfully affects perceivers' responses to faces, promoting biases in attention, classification, and memory. To account for these diverse effects, we propose a model that integrates social cognitive work with two prominent accounts of visual processing: perceptual learning and predictive coding. Our argument is that differential experience with a racial ingroup promotes both (a) perceptual enrichment, including richer, more well-integrated visual representations of ingroup relative to outgroup faces, and (b) expectancies that ingroup faces are normative, which influence subsequent visual processing. By allowing for "top-down" expectancy-based processes, this model accounts for both experience- and non-experience-based influences, such as motivation, context, and task instructions. Fundamentally, we suggest that we treat race as an important psychological dimension because it structures our social environment, which in turn structures mental representation.

Priming Race in Biracial Observers Affects Visual Search for Black and White Faces

We examined whether or not priming racial identity would influence Black-White biracial individuals' ability to visually search for White and Black faces. Black, White, and biracial participants performed a visual search task in which the targets were Black or White faces. Before the task, the biracial participants were primed with either their Black or their White racial identity. All participant groups detected Black faces faster than White faces. Critically, the results also showed a racial-prime effect in biracial individuals: The magnitude of the search asymmetry was significantly different for those primed with their White identity and those primed with their Black identity. These findings suggest that top-down factors such as one's racial identity can influence mechanisms underlying the visual search for faces of different races.

Learning Race from Face: A Survey

Faces convey a wealth of social signals, including race, expression, identity, age and gender, all of which have attracted increasing attention from multi-disciplinary research, such as psychology, neuroscience, computer science, to name a few. Gleaned from recent advances in computer vision, computer graphics, and machine learning, computational intelligence based racial face analysis has been particularly popular due to its significant potential and broader impacts in extensive real-world applications, such as security and defense, surveillance, human computer interface (HCI), biometric-based identification, among others. These studies raise an important question: How implicit, non-declarative racial category can be conceptually modeled and quantitatively inferred from the face? Nevertheless, race classification is challenging due to its ambiguity and complexity depending on context and criteria. To address this challenge, recently, significant efforts have been reported toward race detection and categorization in the community. This survey provides a comprehensive and critical review of the state-of-the-art advances in face-race perception, principles, algorithms, and applications. We first discuss race perception problem formulation and motivation, while highlighting the conceptual potentials of racial face processing. Next, taxonomy of feature representational models, algorithms, performance and racial databases are presented with systematic discussions within the unified learning scenario. Finally, in order to stimulate future research in this field, we also highlight the major opportunities and challenges, as well as potentially important cross-cutting themes and research directions for the issue of learning race from face.

Fluid Movement and Fluid Social Cognition

Rigid social categorization can lead to negative social consequences such as stereotyping and prejudice. The authors hypothesized that bodily experiences of fluidity would promote fluidity in social-categorical thinking. Across a series of experiments, fluid movements compared with nonfluid movements led to more fluid lay theories of social categories, more fluidity in social categorization, and consequences of fluid social-categorical thinking, decreased stereotype endorsement, and increased concern for social inequalities. The role of sensorimotor states in fluid social cognition, with consequences for social judgment and behavior, is discussed.

Male and female faces are only perceived categorically when linked to familiar identities--and when in doubt, he is a male

Categorical perception (CP) is a fundamental cognitive process that enables us to sort similar objects in the world into meaningful categories with clear boundaries between them. CP has been found for high-level stimuli like human faces, more precisely, for the perception of face identity, expression and ethnicity. For sex however, which represents another important and biologically relevant dimension of human faces, results have been equivocal so far. Here, we reinvestigate CP for sex using newly created face stimuli to control two factors that to our opinion might have influenced the results in earlier studies. Our new stimuli are (a) derived from single face identities, so that changes of sex are not confounded with changes of identity information, and (b) "normalized" in their degree of maleness and femaleness, to counteract natural variations of perceived masculinity and femininity of faces that might obstruct evidence of categorical perception. Despite careful normalization, we did not find evidence of CP for sex using classical test procedures, unless participants were specifically familiarized with the face identities before testing. These results support the single-route hypothesis, stating that sex and identity information in faces are not processed in parallel, in contrast to what was suggested in the classical Bruce and Young model of face perception. Besides, interestingly, our participants show a consistent bias, before and after perceptual normalization of the male-female range of the test morph continua, to judge faces as male rather than female.

FEATURE SELECTION AND EXTRACTION USING AN UNSUPERVISED BIOLOGICALLY-SUGGESTED APPROXIMATION TO GEBELEIN'S MAXIMAL CORRELATION

Feature selection and extraction are critical steps in many areas where pattern recognition techniques are applied. Feature selection and extraction are based on identifying and maximizing dependency relations. Gebelein's Maximal Correlation (GMC) is the most general form of dependence in that it does not make any statistical assumptions concerning the nature of the dependencies. Unfortunately, benefiting from such a useful measure in practice is generally impossible as there are only a few cases for which explicit formulae are available to calculate it. In this paper, we point out a parallel between GMC and the SINBAD algorithms, developed originally as a model of feature extraction for neurons in the cerebral cortex. We use SINBAD as a robust approximation to GMC to perform feature selection and extraction on a number of artificial and real datasets. We show that SINBAD estimates of GMC compare favorably to other well known feature selection and extraction methods based on mutual information, kernel canonical correlation analysis and principal component analysis.

Looking the part: social status cues shape race perception

It is commonly believed that race is perceived through another's facial features, such as skin color. In the present research, we demonstrate that cues to social status that often surround a face systematically change the perception of its race. Participants categorized the race of faces that varied along White-Black morph continua and that were presented with high-status or low-status attire. Low-status attire increased the likelihood of categorization as Black, whereas high-status attire increased the likelihood of categorization as White; and this influence grew stronger as race became more ambiguous (Experiment 1). When faces with high-status attire were categorized as Black or faces with low-status attire were categorized as White, participants' hand movements nevertheless revealed a simultaneous attraction to select the other race-category response (stereotypically tied to the status cue) before arriving at a final categorization. Further, this attraction effect grew as race became more ambiguous (Experiment 2). Computational simulations then demonstrated that these effects may be accounted for by a neurally plausible person categorization system, in which contextual cues come to trigger stereotypes that in turn influence race perception. Together, the findings show how stereotypes interact with physical cues to shape person categorization, and suggest that social and contextual factors guide the perception of race.

Looking the part: social status cues shape race perception

It is commonly believed that race is perceived through another's facial features, such as skin color. In the present research, we demonstrate that cues to social status that often surround a face systematically change the perception of its race. Participants categorized the race of faces that varied along White-Black morph continua and that were presented with high-status or low-status attire. Low-status attire increased the likelihood of categorization as Black, whereas high-status attire increased the likelihood of categorization as White; and this influence grew stronger as race became more ambiguous (Experiment 1). When faces with high-status attire were categorized as Black or faces with low-status attire were categorized as White, participants' hand movements nevertheless revealed a simultaneous attraction to select the other race-category response (stereotypically tied to the status cue) before arriving at a final categorization. Further, this attraction effect grew as race became more ambiguous (Experiment 2). Computational simulations then demonstrated that these effects may be accounted for by a neurally plausible person categorization system, in which contextual cues come to trigger stereotypes that in turn influence race perception. Together, the findings show how stereotypes interact with physical cues to shape person categorization, and suggest that social and contextual factors guide the perception of race.

Own-species bias in the representations of monkey and human face categories in the primate temporal lobe

Face categorization is fundamental for social interactions of primates and is crucial for determining conspecific groups and mate choice. Current evidence suggests that faces are processed by a set of well-defined brain areas. What is the fine structure of this representation, and how is it affected by visual experience? Here, we investigated the neural representations of human and monkey face categories using realistic three-dimensional morphed faces that spanned the continuum between the two species. We found an "own-species" bias in the categorical representation of human and monkey faces in the monkey inferior temporal cortex at the level of single neurons as well as in the population response analyzed using a pattern classifier. For monkey and human subjects, we also found consistent psychophysical evidence indicative of an own-species bias in face perception. For both behavioural and neural data, the species boundary was shifted away from the center of the morph continuum, for each species toward their own face category. This shift may reflect visual expertise for members of one's own species and be a signature of greater brain resources assigned to the processing of privileged categories. Such boundary shifts may thus serve as sensitive and robust indicators of encoding strength for categories of interest.

Categorical perception for unfamiliar faces. The effect of covert and overt face learning

Robust findings show that categorical perception (CP) occurs in identification of familiar faces. CP has also been observed for unfamiliar morphed faces after sufficient learning of the original, unmorphed faces has taken place. We previously suggested that CP arises when the activation of inconsistent visual and verbal representations creates a conflict between perceptual and category information. In the present study, we conducted two experiments in which the endpoint faces of an unfamiliar morphed continuum were presented in either a covert training regime (famous vs. nonfamous judgments) or an overt training regime (previously seen vs. unseen judgments). In both experiments, participants' reaction times to repeated targets decreased relative to reaction times to control items during training. After overt training, CP was observed for the previously unfamiliar faces. No CP was observed for covertly trained faces. We conclude that individual faces must be explicitly categorized before CP can be established for the morphed continuum between them.

Face familiarity, distinctiveness, and categorical perception

Four experiments with faces support the original interpretation of categorical perception (CP) as only present for familiar categories. Unlike in the results of Levin and Beale (2000), no evidence is found for face identity CP with unfamiliar faces. Novel face identities were shown to be capable of encoding for immediate sorting purposes but the representations utilized do not have the format of perceptual categories. One possibility explored was that a choice of a distinctive face as an end-point in a morphed continuum can spuriously produce effects that resemble CP. Such morphed continua provided unequal psychological responses to equal physical steps though much more so in a better likeness paradigm than for forced-choice recognition. Thus, researchers doing almost the same experiments may produce very different results and come to radically different conclusions.

The other-race effect for face perception: an event-related potential study

It is well known that a recognition bias can be observed whenever subjects have to decide whether they have seen a person before that belongs to a different ethnical group. Although this "other-race effect" is well documented on a behavioural level, its underlying mechanisms remain unclear. One plausible explanation might be that cortical areas involved in face processing are not as effective for other-race faces due to a missing experience with individuals from other ethnical groups. This interpretation is strongly supported by a functional magnetic resonance imaging study showing decreased brain activity on other-race faces. Furthermore, two event-related potential studies revealed differences in brain activity in the first 250 ms after face presentation, but with inconsistent results. Therefore, we investigated 12 Caucasian subjects, showing them faces of Asian and Caucasian subjects in a perceptual priming paradigm and measured the event-related brain potentials. On a behavioural level we found slower reaction times to Asian faces compared to Caucasian faces in the unprimed condition, reflecting a deficit for Caucasian subjects to process other-race faces. In accordance with these behavioural data we see a significantly reduced late N250r amplitude in the unprimed condition to the Asian faces compared to the Caucasian faces. These results clearly indicate that the other-race effect was present in our sample and very specific only in the unprimed condition around 350-450 ms after stimulus onset.

Measuring individual differences in sensitivities to basic emotions in faces

The assessment of individual differences in facial expression recognition is normally required to address two major issues: (1) high agreement level (ceiling effect) and (2) differential difficulty levels across emotions. We propose a new assessment method designed to quantify individual differences in the recognition of the six basic emotions, 'sensitivities to basic emotions in faces.' We attempted to address the two major assessment issues by using morphing techniques and item response theory (IRT). We used morphing to create intermediate, mixed facial expression stimuli with various levels of recognition difficulty. Applying IRT enabled us to estimate the individual latent trait levels underlying the recognition of respective emotions (sensitivity scores), unbiased by stimulus properties that constitute difficulty. In a series of two experiments we demonstrated that the sensitivity scores successfully addressed the two major assessment issues and their concomitant individual variability. Intriguingly, correlational analyses of the sensitivity scores to different emotions produced orthogonality between happy and non-happy emotion recognition. To our knowledge, this is the first report of the independence of happiness recognition, unaffected by stimulus difficulty.

Conceptual interrelatedness and caricatures

Concepts are interrelated to the extent that the characterization of each concept is influenced by the other concepts, and are isolated to the extent that the characterization of one concept is independent of other concepts. The relative categorization accuracy of the prototype and caricature of a concept can be used as a measure of concept interrelatedness. The prototype is the central tendency of a concept, whereas a caricature deviates from the concept's central tendency in the direction opposite the central tendency of other acquired concepts. The prototype is predicted to be relatively well categorized when a concept is relatively independent of other concepts, but the caricature is predicted to be relatively well categorized when a concept is highly related to other concepts. Support for these predictions comes from manipulations of the labels given to simultaneously acquired concepts (Experiment 1) and of the order of categories during learning (Experiment 2).