For Your Local Eyes Only: Culture-Specific Face Typicality Influences Perceptions of Trustworthiness

Implicit bias and experience influence overall but not relative trustworthiness judgment of other-race faces

Impressions of trustworthiness are formed quickly from faces. To what extent are these impressions shared among observers of the same or different races? Although high consensus of trustworthiness evaluation has been consistently reported, recent studies suggested substantial individual differences. For instance, negative implicit racial bias and low contact experience towards individuals of the other race have been shown to be related to low trustworthiness judgments for other-race faces. This pre-registered study further examined the effects of implicit social bias and experience on trustworthiness judgments of other-race faces. A relatively large sample of White (N = 338) and Black (N = 299) participants completed three tasks: a trustworthiness rating task of faces, a race implicit association test, and a questionnaire of experience. Each participant rated trustworthiness of 100 White faces and 100 Black faces. We found that the overall trustworthiness ratings for other-race faces were influenced by both implicit bias and experience with individuals of the other-race. Nonetheless, when comparing to the own-race baseline ratings, high correlations were observed for the relative differences in trustworthiness ratings of other-race faces for participants with varied levels of implicit bias and experience. These results suggest differential impact of social concepts (e.g., implicit bias, experience) vs. instinct (e.g., decision of approach-vs-avoid) on trustworthiness impressions, as revealed by overall vs. relative ratings on other-race faces.

When Trustworthiness Meets Face: Facial Design for Social Robots

As a technical application in artificial intelligence, a social robot is one of the branches of robotic studies that emphasizes socially communicating and interacting with human beings. Although both robot and behavior research have realized the significance of social robot design for its market success and related emotional benefit to users, the specific design of the eye and mouth shape of a social robot in eliciting trustworthiness has received only limited attention. In order to address this research gap, our study conducted a 2 (eye shape) × 3 (mouth shape) full factorial between-subject experiment. A total of 211 participants were recruited and randomly assigned to the six scenarios in the study. After exposure to the stimuli, perceived trustworthiness and robot attitude were measured accordingly. The results showed that round eyes (vs. narrow eyes) and an upturned-shape mouth or neutral mouth (vs. downturned-shape mouth) for social robots could significantly improve people's trustworthiness and attitude towards social robots. The effect of eye and mouth shape on robot attitude are all mediated by the perceived trustworthiness. Trustworthy human facial features could be applied to the robot's face, eliciting a similar trustworthiness perception and attitude. In addition to empirical contributions to HRI, this finding could shed light on the design practice for a trustworthy-looking social robot.

Visual analysis of trustworthiness studies: based on the Web of Science database

Trustworthiness is the most significant predictor of trust and has a significant impact on people's levels of trust. Most trustworthiness-related research is empirical, and while it has a long history, it is challenging for academics to get insights that are applicable to their fields of study and to successfully transfer fragmented results into practice. In order to grasp their dynamic development processes through the mapping of network knowledge graphs, this paper is based on the Web of Science database and uses CiteSpace (6.2.R4) software to compile and visualize the 1,463 publications on trustworthy studies over the past 10 years. This paper aims to provide valuable references to theoretical research and the practice of Trustworthiness. The findings demonstrate that: over the past 10 years, trustworthiness-related research has generally increased in volume; trustworthiness research is concentrated in industrialized Europe and America, with American research findings having a bigger global impact; The University of California System, Harvard University, and Yale University are among the high-production institutions; the leading figures are represented by Alexander Todorov, Marco Brambilla, Bastian Jaeger, and others; the core authors are distinguished university scholars; however, the level of cooperation of the core author needs to be improved. The primary journal for publishing research on trustworthiness is the Journal of Personality and Social Psychology and Biology Letters. In addition, the study focuses on three distinct domains, involving social perception, facial clues, and artificial intelligence.

Contextual modulation of appearance-trait learning

When we encounter a stranger for the first time, we spontaneously attribute to them a wide variety of character traits based on their facial appearance. There is increasing consensus that learning plays a key role in these first impressions. According to the Trait Inference Mapping (TIM) model, first impressions are the products of mappings between 'face space' and 'trait space' acquired through domain-general associative processes. Drawing on the associative learning literature, TIM predicts that first-learned associations between facial appearance and character will be particularly influential: they will be difficult to unlearn and will be more likely to generalise to novel contexts than appearance-trait associations acquired subsequently. The study of face-trait learning de novo is complicated by the fact that participants, even young children, already have extensive experience with faces before they enter the lab. This renders the study of first-learned associations from faces intractable. Here, we overcome this problem by using Greebles - a class of novel synthetic objects about which participants had no previous knowledge or preconceptions - as a proxy for faces. In four experiments (total N = 640) with adult participants we adapt classic AB-A and AB-C renewal paradigms to study appearance-trait learning. Our results indicate that appearance-trait associations are subject to contextual control, and are resistant to counter-stereotypical experience.

Registered report: Social face evaluation: ethnicity-specific differences in the judgement of trustworthiness of faces and facial parts

Social face evaluation is a common and consequential element of everyday life based on the judgement of trustworthiness. However, the particular facial regions that guide such trustworthiness judgements are largely unknown. It is also unclear whether different facial regions are consistently utilized to guide judgments for different ethnic groups, and whether previous exposure to specific ethnicities in one's social environment has an influence on trustworthiness judgements made from faces or facial regions. This registered report addressed these questions through a global online survey study that recruited Asian, Black, Latino, and White raters (N = 4580). Raters were shown full faces and specific parts of the face for an ethnically diverse, sex-balanced set of 32 targets and rated targets' trustworthiness. Multilevel modelling showed that in forming trustworthiness judgements, raters relied most strongly on the eyes (with no substantial information loss vis-à-vis full faces). Corroborating ingroup-outgroup effects, raters rated faces and facial parts of targets with whom they shared their ethnicity, sex, or eye color as significantly more trustworthy. Exposure to ethnic groups in raters' social environment predicted trustworthiness ratings of other ethnic groups in nuanced ways. That is, raters from the ambient ethnic majority provided slightly higher trustworthiness ratings for stimuli of their own ethnicity compared to minority ethnicities. In contrast, raters from an ambient ethnic minority (e.g., immigrants) provided substantially lower trustworthiness ratings for stimuli of the ethnic majority. Taken together, the current study provides a new window into the psychological processes underlying social face evaluation and its cultural generalizability. PROTOCOL REGISTRATION: The stage 1 protocol for this Registered Report was accepted in principle on 7 January 2022. The protocol, as accepted by the journal, can be found at: https://doi.org/10.6084/m9.figshare.18319244 .

Enhanced source memory for cheaters with higher resemblance to own-culture typical faces

Recent evidence suggests that culture-specific face typicality has an impact on making trait judgments. Additionally, facial resemblance to one's culture-typical faces causes them to be perceived as reliable, less dangerous, and more accurately recognized. When judging persons from other cultural origins, one's own culture's face standards might shape inferences, behavior, and memory. In this study, the partners' facial resemblance to participants' culturally typical faces was manipulated using target faces, considered to be higher or lower, similar to people living in the participants' hometown. Participants were asked to invest in a company together with partners who have a higher and lower resemblance to their own-culture typical faces in a cooperation game. The results showed that facial resemblance to own-culture typical faces affected investment preferences. Partners with a higher resemblance to own-culture typical faces were more correctly distinguished in the old-new recognition memory task. The study found that partners with a higher resemblance to own-culture typical faces had a source memory advantage for cheating behaviors. These results confirmed that a higher resemblance to own-culture typical faces provide an advantage in cross-cultural interactions, allowing them to become better recognized. Additionally, enhanced source memory for cheaters with higher resemblance to own-culture typical faces may indicate a flexible cognitive system that is sensitive to information that violates social expectations.

Sensitivity to trustworthiness cues in own- and other-race faces: The role of spatial frequency information

Research has shown that adults are better at processing faces of the most represented ethnic group in their social environment compared to faces from other ethnicities, and that they rely more on holistic/configural information for identity discrimination in own-race than other-race faces. Here, we applied a spatial filtering approach to the investigation of trustworthiness perception to explore whether the information on which trustworthiness judgments are based differs according to face race. European participants (N = 165) performed an online-delivered pairwise preference task in which they were asked to select the face they would trust more within pairs randomly selected from validated White and Asian broad spectrum, low-pass filter and high-pass filter trustworthiness continua. Results confirmed earlier demonstrations that trustworthiness perception generalizes across face ethnicity, but discrimination of trustworthiness intensity relied more heavily on the LSF content of the images for own-race faces compared to other-race faces. Results are discussed in light of previous work on emotion discrimination and the hypothesis of overlapping perceptual mechanisms subtending social perception of faces.

The Compositionality of Facial Expressions

The principle of compositionality, an important postulation in language and cognition research, posits that the meaning of a complex expression is determined by the meaning of its constituting parts and the operation performed on those parts. Here, we provide strong evidence that this principle plays a significant role also in interpreting facial expressions. In three studies in which perceivers interpreted sequences of two emotional facial expression images, we show that the composite meaning of facial expressions results from the meaning of its constituting expressions and an algebraic operation performed on those expressions. Our study offers a systematic account as to how the meaning of facial expressions (single and sequences) are being formed and perceived. In a broader context, our results raise the possibility that the principle of compositionality may apply to human communication modalities beyond spoken language, whereby a minimal number of components are expanded to a much greater number of meanings.

Culture-free perceptual invariant for trustworthiness

Humans beings decide to trust others selectively, often based on the appearance of a face. But how do observers deal with the wide variety of facial morphologies and, in particular, those outside their own familiar cultural group? Using reverse correlation, a data-driven approach to explore how individuals create internal representations without external biases, we studied the generation of trustworthy faces by French and Chinese participants (N = 160) within and outside their own cultural group. Participants selected the most trustworthy or attractive (control condition) face from two identical European or Asian descent faces that had been modified by different noise masks. A conjunction analysis to reveal facial features common to both cultures showed that Chinese and French participants unconsciously increased the contrast of the "pupil-iris area" to make the face appear more trustworthy. No significant effects common to both groups were found for the attraction condition suggesting that attraction judgements are dependent on cultural processes. These results suggest the presence of universal cross-cultural mechanisms for the construction of implicit first impressions of trust, and highlight the importance of the eyes area in this process.

Human face and gaze perception is highly context specific and involves bottom-up and top-down neural processing

This review summarizes human perception and processing of face and gaze signals. Face and gaze signals are important means of non-verbal social communication. The review highlights that: (1) some evidence is available suggesting that the perception and processing of facial information starts in the prenatal period; (2) the perception and processing of face identity, expression and gaze direction is highly context specific, the effect of race and culture being a case in point. Culture affects by means of experiential shaping and social categorization the way in which information on face and gaze is collected and perceived; (3) face and gaze processing occurs in the so-called 'social brain'. Accumulating evidence suggests that the processing of facial identity, facial emotional expression and gaze involves two parallel and interacting pathways: a fast and crude subcortical route and a slower cortical pathway. The flow of information is bi-directional and includes bottom-up and top-down processing. The cortical networks particularly include the fusiform gyrus, superior temporal sulcus (STS), intraparietal sulcus, temporoparietal junction and medial prefrontal cortex.

Trustworthy faces make people more risk-tolerant: The effect of facial trustworthiness on risk decision-making under gain and loss conditions

People can judge a stranger's trustworthiness at first glance solely based on facial appearance. Moreover, the trust behaviors people exhibit toward strangers differ depending on perceived trustworthiness from faces. Research has found that people have different risk preferences according to the gain or loss frame. Therefore, we hypothesized that the risk decisions are differently affected by facial trustworthiness in different frames. We conducted three experiments in which we asked participants to make risk decisions in the gain frame or loss frame. The results revealed that facial trustworthiness had a significant effect on risk decisions in the gain frame. However, the effect was attenuated in the loss frame. These results suggest that people are more willing to take risks in the gain frame if individuals look more trustworthy than those who look untrustworthy.

Which Facial Features Are Central in Impression Formation?

Which facial characteristics do people rely on when forming personality impressions? Previous research has uncovered an array of facial features that influence people’s impressions. Even though some (classes of) features, such as resemblances to emotional expressions or facial width-to-height ratio (fWHR), play a central role in theories of social perception, their relative importance in impression formation remains unclear. Here, we model faces along a wide range of theoretically important dimensions and use machine learning techniques to test how well 28 features predict impressions of trustworthiness and dominance in a diverse set of 597 faces. In line with overgeneralization theory, emotion resemblances were most predictive of both traits. Other features that have received a lot of attention in the literature, such as fWHR, were relatively uninformative. Our results highlight the importance of modeling faces along a wide range of dimensions to elucidate their relative importance in impression formation.

Typical is Trustworthy - Evidence for a Generalized Heuristic

When judging whether someone is trustworthy, people rely on the perceptual typicality of a person’s face. We tested whether a more general typical-is-trustworthy heuristic exists based on the descriptive typicality of a person. In four experiments, we provided participants with descriptive information about the typicality of target persons’ attributes (i.e., population prevalence) and measured perceived trustworthiness. Participants consistently expected descriptively typical targets to be more trustworthy than descriptively atypical targets. These findings show that typicality-based trustworthiness inferences are not only confided to perceptual typicality but also apply to descriptive typicality, suggesting a general typical-is-trustworthiness heuristic. This implies a human tendency to trust typical individuals more and, conversely, a disadvantage for atypical individuals such as minorities.

Parents reinforce the formation of first impressions in conversation with their children

The tendency to form first impressions from facial appearance emerges early in development. One route through which these impressions may be learned is parent-child interaction. In Study 1, 24 parent-child dyads (children aged 5–6 years, 50% male, 83% White British) were given four computer generated faces and asked to talk about each of the characters shown. Study 2 (children aged 5–6 years, 50% male, 92% White British) followed a similar procedure using images of real faces. Across both studies, around 13% of conversation related to the perceived traits of the individuals depicted. Furthermore, parents actively reinforced their children’s face-trait mappings, agreeing with the opinions they voiced on approximately 40% of occasions across both studies. Interestingly, although parents often encouraged face-trait mappings in their children, their responses to questionnaire items suggested they typically did not approve of judging others based on their appearance.

The Nonlinear and Gender-Related Relationships of Face Attractiveness and Typicality With Perceived Trustworthiness

Perceived trustworthiness is one of the most important facial traits in social interaction. To elucidate how facial trustworthiness is assessed by others and its relationship to other facial traits would have significant theoretical and practical implications. Prior studies have shown that perceived attractiveness and typicality of a face may contribute to trustworthiness judgments; i.e., trustworthy faces are always the typical and attractive ones. Here, by conducting judgments of facial traits (i.e., trustworthiness, attractiveness, and typicality) on the same set of faces, we revealed a more profound relationship among these facial traits. First, we found that trustworthiness judgments did not always peak at the average face, in contrast to previous research. Second, trustworthiness exhibited a nonlinear relationship with attractiveness and typicality: Men relied more on typicality when judging a face as untrustworthy or neutral, whereas women relied more on typicality when judging a face as untrustworthy but more on attractiveness when judging a face as trustworthy. Third, women and men may utilize different traits to evaluate face trustworthiness: The relationship between trustworthiness and typicality judgments was closer in men than in women, whereas women counted on face attractiveness more than men did to evaluate face trustworthiness. These findings demonstrate that judging the trustworthiness of a face is a more complex process than previously thought, which may lead to a better understanding of the mechanisms underlying highly flexible and sophisticated social interactions in humans.

First impressions of child faces: Facial trustworthiness influences adults' interpretations of children's behavior in ambiguous situations

Despite the profound behavioral consequences that first impressions of trustworthiness have on adult populations, few studies have examined how adults' first impressions of trustworthiness influence behavioral outcomes for children. Using a novel task design, we examined adults' perceptions of children's behavior in ambiguous situations. After a brief presentation of a child's face (high trust or low trust), participants viewed the child's face embedded within an ambiguous scene involving two children (Scene Task) or read a vignette about a misbehavior done by that child (Misbehavior Task). In the Scene Task, participants described what they believed to be happening in each scene; in the Misbehavior Task, participants indicated whether the behavior was done on purpose or by accident. In both tasks, participants also rated the behavior of the target child and indicated whether that child would be a good friend. In Experiment 1, young adults (n = 61) and older adults (n = 57) viewed unaltered face images. In Experiment 2, young adults (N = 59) completed the same tasks while viewing images of child faces morphed toward high-trust and low-trust averages. In both experiments, ambiguous scenes and misbehaviors were interpreted more positively when the target child had a high-trust face versus a low-trust face, with comparable patterns of results for the two age groups. Collectively, our results demonstrate that a child's facial trustworthiness biases how adults interpret children's behavior-a heuristic that may have lasting behavioral consequences for children through a self-fulfilling prophecy.

From likely to likable: The role of statistical typicality in human social assessment of faces

Humans readily form social impressions, such as attractiveness and trustworthiness, from a stranger's facial features. Understanding the provenance of these impressions has clear scientific importance and societal implications. Motivated by the efficient coding hypothesis of brain representation, as well as Claude Shannon's theoretical result that maximally efficient representational systems assign shorter codes to statistically more typical data (quantified as log likelihood), we suggest that social "liking" of faces increases with statistical typicality. Combining human behavioral data and computational modeling, we show that perceived attractiveness, trustworthiness, dominance, and valence of a face image linearly increase with its statistical typicality (log likelihood). We also show that statistical typicality can at least partially explain the role of symmetry in attractiveness perception. Additionally, by assuming that the brain focuses on a task-relevant subset of facial features and assessing log likelihood of a face using those features, our model can explain the "ugliness-in-averageness" effect found in social psychology, whereby otherwise attractive, intercategory faces diminish in attractiveness during a categorization task.

A new data-driven mathematical model dissociates attractiveness from sexual dimorphism of human faces

Human facial attractiveness is evaluated by using multiple cues. Among others, sexual dimorphism (i.e. masculinity for male faces/femininity for female faces) is an influential factor of perceived attractiveness. Since facial attractiveness is judged by incorporating sexually dimorphic traits as well as other cues, it is theoretically possible to dissociate sexual dimorphism from facial attractiveness. This study tested this by using a data-driven mathematical modelling approach. We first analysed the correlation between perceived masculinity/femininity and attractiveness ratings for 400 computer-generated male and female faces (Experiment 1) and found positive correlations between perceived femininity and attractiveness for both male and female faces. Using these results, we manipulated a set of faces along the attractiveness dimension while controlling for sexual dimorphism by orthogonalisation with data-driven mathematical models (Experiment 2). Our results revealed that perceived attractiveness and sexual dimorphism are dissociable, suggesting that there are as yet unidentified facial cues other than sexual dimorphism that contribute to facial attractiveness. Future studies can investigate the true preference of sexual dimorphism or the genuine effects of attractiveness by using well-controlled facial stimuli like those that this study generated. The findings will be of benefit to the further understanding of what makes a face attractive.

Tracking historical changes in trustworthiness using machine learning analyses of facial cues in paintings

Social trust is linked to a host of positive societal outcomes, including improved economic performance, lower crime rates and more inclusive institutions. Yet, the origins of trust remain elusive, partly because social trust is difficult to document in time. Building on recent advances in social cognition, we design an algorithm to automatically estimate ratings of perceived trustworthiness evaluations from specific facial cues (such as muscle contractions associated with smiling) detected in European portraits in large historical databases. We used this measure as a proxy of social trust in history. Our results show that estimated levels of perceived trustworthiness in portraits increased over the period 1500–2000. Further analyses suggest that this rise of perceived trustworthiness is associated with increased living standards.

Quantifying how social trust evolved throughout history can help us understand the long-run dynamics of our societies. Here, the authors show an increase in displays of trustworthiness, using a face processing algorithm on early to modern European portraits.

How Ethnicity, Expression, and Study Design Influence First Impressions of Approachability

Over two studies, participants (total N = 642) rated a community sample of photographs of Black, East Asian, and White males who were smiling or portraying a neutral expression to see how participant ethnicity, target ethnicity, and target expression influence judgments of approachability (i.e., trustworthiness, friendliness, and threat). We also examined how a commonly used study design, in which each participant is asked to evaluate different groups of people, may motivate participants to adjust their ratings in an effort to avoid appearing biased. Results showed that the White participant group tended to rate smiling targets as friendlier (Studies 1 and 2) and more trustworthy (Study 1) than did the non-White participant group, which could be due to cultural differences based on majority versus minority status among the participants. In addition, the White participant group tended to rate White targets more positively than did the non-White participant group, suggesting an in-group bias. Finally, differences in results between Studies 1 and 2 suggest that study design can influence the degree of bias responding, highlighting the importance of incorporating a diversity of methods to better understand first impression judgments.

Swiping right: face perception in the age of Tinder

With an estimated 50 million or more users worldwide, Tinder has become one of the most popular mobile dating applications. Although judgments of physical attractiveness are assumed to drive the "swiping" decisions that lead to matches, we propose that there is an additional evaluative dimension driving behind these decisions: judgments of moral character. With the aim of adding empirical support for this proposition, we critically review the most striking findings about first impressions extracted from faces, moral character in person perception, creepiness, and the uncanny valley, as they apply to Tinder behavior. Drawing on this research and the evolutionary theory of biological markets, we formulate several hypotheses that offer directions for future studies of Tinder and other dating apps. We conclude that research on face perception of novel targets supports the plausibility of moral character as a potential factor affecting the swiping decisions and subsequent behavior of Tinder users.

Psychological origins of the Industrial Revolution: More work is needed!

I am grateful to have received so many stimulating commentaries from interested colleagues regarding the psychological origins of the Industrial Revolution and the role of evolutionary theory in understanding historical phenomena. Commentators criticized, extended, and explored the implications of the perspective I presented, and I wholeheartedly agree with many commentaries that more work is needed. In this response, I thus focus on what is needed to further test the psychological origins of the Industrial Revolution. Specifically, I argue, in agreement with many commentators, that we need: (1) better data about standards of living, psychological preferences, and innovation rates (sect. R1); (2) better models to understand the role of resources (and not just mortality) in driving cultural evolution and the multiple aspects of the behavioral constellation of affluence (sect. R2); and (3) better predictions and better statistical instruments to disentangle the possible mechanisms behind the rise of innovativeness (genetic selection, rational choice, and phenotypic plasticity) (sect. R3).

Dynamic interactive theory as a domain-general account of social perception

The perception of social categories, emotions, and personality traits from others' faces each have been studied extensively but in relative isolation. We synthesize emerging findings suggesting that, in each of these domains of social perception, both a variety of bottom-up facial features and top-down social cognitive processes play a part in driving initial perceptions. Among such top-down processes, social-conceptual knowledge in particular can have a fundamental structuring role in how we perceive others' faces. Extending the Dynamic Interactive framework (Freeman & Ambady, 2011), we outline a perspective whereby the perception of social categories, emotions, and traits from faces can all be conceived as emerging from an integrated system relying on domain-general cognitive properties. Such an account of social perception would envision perceptions to be a rapid, but gradual, process of negotiation between the variety of visual cues inherent to a person and the social cognitive knowledge an individual perceiver brings to the perceptual process. We describe growing evidence in support of this perspective as well as its theoretical implications for social psychology.

Trust, Sexual Trust, and Sexual Health: An Interrogative Review

Trust is experienced almost constantly in all forms of social and interpersonal relationships, including sexual relationships, and may contribute both directly and indirectly to sexual health. The purpose of this review is to link three aspects of trust to sexual health: (1) the role of trust in sexual relationships; (2) the role of trust in sexually transmitted infection (STI) prevention, particularly condom use; and (3) the relevance of trust in sexual relationships outside of the traditional model of monogamy. The review ends with consideration of perspectives that could guide new research toward understanding the enigmas of trust in partnered sexual relations in the context of sexual and public health.

The effect of sexual selection on phenotypic diversification among human populations: A simulation study

Despite the generally low level of inter-population genetic differentiation in humans as compared with great apes, it has long been acknowledged that there is a considerable amount of geographic variations in human phenotypes, for example, skin pigmentation, cranial morphology, and soft-tissue facial morphology, to name but a few. Indeed, recent studies have suggested that the extent of inter-population diversity in some human phenotypes is greater than expected from random drift alone. Such an excess of phenotypic diversity is often attributed to adaptation to local environment. However, this account is valid only if populations differ in some ecological aspects that elicit differential selection acting on a given phenotypic feature. Another long-standing hypothesis is the sexual selection hypothesis, which claims that phenotypic diversity arises and/or is maintained owing to variations in preference for mating partners. In this paper, we explore the plausibility of the sexual selection hypothesis by means of computer simulations, in which the inter-population diversity of a quantitative trait is evaluated against the expectation from random drift, using the Q_ST-F_ST comparison. As possible driving factors of sexual selection, we consider two types of mate-choice preference: preference for the population average and preference for a culturally-transmitted arbitrary trend. Our simulations suggest that sexual selection can, under certain circumstances, maintain and/or generate a detectable amount of inter-population phenotypic diversity, even when populations are ecologically identical and loosely connected to each other by mutual migration. Since mating decisions in humans are considerably affected by social learning, human mate-choice preference may be more readily diversified between populations than in other animals. We suggest, therefore, that some of the observed human phenotypic variations may be better understood as a product of cultural, rather than ecological, diversification.

Toward a New Approach to Cross-Cultural Distinctiveness and Typicality of Human Faces: The Cross-Group Typicality/ Distinctiveness Metric

In the present research, we took advantage of geometric morphometrics to propose a data-driven method for estimating the individual degree of facial typicality/distinctiveness for cross-cultural (and other cross-group) comparisons. Looking like a stranger in one’s home culture may be somewhat stressful. The same facial appearance, however, might become advantageous within an outgroup population. To address this fit between facial appearance and cultural setting, we propose a simple measure of distinctiveness/typicality based on position of an individual along the axis connecting the facial averages of two populations under comparison. The more distant a face is from its ingroup population mean toward the outgroup mean the more distinct it is (vis-à-vis the ingroup) and the more it resembles the outgroup standards. We compared this new measure with an alternative measure based on distance from outgroup mean. The new measure showed stronger association with rated facial distinctiveness than distance from outgroup mean. Subsequently, we manipulated facial stimuli to reflect different levels of ingroup-outgroup distinctiveness and tested them in one of the target cultures. Perceivers were able to successfully distinguish outgroup from ingroup faces in a two-alternative forced-choice task. There was also some evidence that this task was harder when the two faces were closer along the axis connecting the facial averages from the two cultures. Future directions and potential applications of our proposed approach are discussed.

Are Rich People Perceived as More Trustworthy? Perceived Socioeconomic Status Modulates Judgments of Trustworthiness and Trust Behavior Based on Facial Appearance

In the era of globalization, people meet strangers from different countries more often than ever. Previous research indicates that impressions of trustworthiness based on facial appearance play an important role in interpersonal cooperation behaviors. The current study examined whether additional information about socioeconomic status (SES), including national prosperity and individual monthly income, affects facial judgments and appearance-based trust decisions. Besides reproducing previous conclusions that trustworthy faces receive more money than untrustworthy faces, the present study showed that high-income individuals were judged as more trustworthy than low-income individuals, and also were given more money in a trust game. However, trust behaviors were not modulated by the nationality of the faces. The present research suggests that people are more likely to trust strangers with a high income, compared with individuals with a low income.

A Dynamic Structure of Social Trait Space

Facial appearance evokes robust impressions of other people's personality traits. Recent research suggests that the trait space arising from face-based impressions shifts due to context and social cognitive factors. We suggest a novel framework in which multiple bottom-up and top-down processes mutually determine a dynamic rather than fixed trait space.