The general age of leadership: older-looking presidential candidates win elections during war

As nation-state leaders age they increasingly engage in inter-state militarized disputes yet in industrialized societies a steady decrease in testosterone associated with aging is observed--which suggests a decrease in dominance behavior. The current paper points out that from modern societies to Old World monkeys increasing both in age and social status encourages dominant strategies to maintain acquired rank. Moreover, it is argued this consistency has shaped an implicit prototype causing followers to associate older age with dominance leadership. It is shown that (i) faces of older leaders are preferred during intergroup conflict and (ii) morphing U.S. Presidential candidates to appear older or younger has an overriding effect on actual election outcomes. This indicates that democratic voting can be systematically adjusted by activating innate biases. These findings appear to create a new line of research regarding the biology of leadership and contextual cues of age.     

Looking Like a Leader–Facial Shape Predicts Perceived Height and Leadership Ability

Judgments of leadership ability from face images predict the outcomes of actual political elections and are correlated with leadership success in the corporate world. The specific facial cues that people use to judge leadership remain unclear, however. Physical height is also associated with political and organizational success, raising the possibility that facial cues of height contribute to leadership perceptions. Consequently, we assessed whether cues to height exist in the face and, if so, whether they are associated with perception of leadership ability. We found that facial cues to perceived height had a strong relationship with perceived leadership ability. Furthermore, when allowed to manually manipulate faces, participants increased facial cues associated with perceived height in order to maximize leadership perception. A morphometric analysis of face shape revealed that structural facial masculinity was not responsible for the relationship between perceived height and perceived leadership ability. Given the prominence of facial appearance in making social judgments, facial cues to perceived height may have a significant influence on leadership selection.     

Facial appearance affects voting decisions

Human groups are unusual among primates in that our leaders are often democratically selected. Faces affect hiring decisions and could influence voting behavior. Here, we show that facial appearance has important effects on choice of leader. We show that differences in facial shape alone between candidates can predict who wins or loses in an election (Study 1) and that changing context from war time to peace time can affect which face receives the most votes (Study 2). Our studies highlight the role of face shape in voting behavior and the role of personal attributions in face perception. We also show that there may be no general characteristics of faces that can win votes, demonstrating that face traits and information about the environment interact in choice of leader.     

Implicit Racial Attitudes Influence Perceived Emotional Intensity on Other-Race Faces

An ability to accurately perceive and evaluate out-group members'' emotions plays a critical role in intergroup interactions. Here we showed that Chinese participants'' implicit attitudes toward White people bias their perception and judgment of emotional intensity of White people''s facial expressions such as anger, fear and sadness. We found that Chinese participants held pro-Chinese/anti-White implicit biases that were assessed in an evaluative implicit association test (IAT). Moreover, their implicit biases positively predicted the perceived intensity of White people''s angry, fearful and sad facial expressions but not for happy expressions. This study demonstrates that implicit racial attitudes can influence perception and judgment of a range of emotional expressions. Implications for intergroup interactions were discussed.     

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.     

Behavioral Immune System and Ingroup Derogation: The Effects of Infectious Diseases on Ingroup Derogation Attitudes

From evolutionary reasoning, we derived a novel hypothesis that ingroup derogation is an evolved response of behavioral immune system which follows the smoke detector principle and the functional flexibility principle. This hypothesis was tested and supported across three experiments. In Experiment 1, participants’ group membership was manipulated by using a minimal group paradigm. The results indicated that mere social categorization alone — a heuristic cue that implies the differentiation between "us" and "them" — was sufficient to elicit ingroup derogation among Chinese participants, and, such an intergroup bias was positively associated with the perceived vulnerability to diseases, which was also more consistently associated with ingroup attitudes. Experiment 2 extended and partially replicated Experiment 1 by showing that when there were cues of diseases in the immediate physical environment, Chinese participants exaggerated their attitudes of ingroup derogation. The results also showed that this effect was mainly driven by outgroup attraction. Experiment 3 changed the method of disease manipulation, and found that Chinese participants responded more strongly to disease cues originating from ingroup members and that they endorsed more ingroup derogation attitudes even when the ingroup and outgroup members were both displaying cues of diseases. Taken together, these results reveal the previously unexplored effects of infectious diseases on ingroup derogation attitudes, and suggest an interesting linkage between the evolved behavioral immune system and the ingroup derogation.     

Think Leader,Think White? Capturing and Weakening an Implicit Pro-White Leadership Bias

Across four studies, we found evidence for an implicit pro-White leadership bias that helps explain the underrepresentation of ethnic minorities in leadership positions. Both White-majority and ethnic minority participants reacted significantly faster when ethnically White names and leadership roles (e.g., manager; Study 1) or leadership traits (e.g., decisiveness; Study 2 & 3) were paired in an Implicit Association Test (IAT) rather than when ethnic minority names and leadership traits were paired. Moreover, the implicit pro-White leadership bias showed discriminant validity with the conventional implicit bias measures (Study 3). Importantly, results showed that the pro-White leadership bias can be weakened when situational cues increase the salience of a dual identity (Study 4). This, in turn, can diminish the explicit pro-White bias in promotion related decision making processes (Study 4). This research offers a new tool to measure the implicit psychological processes underlying the underrepresentation of ethnic minorities in leadership positions and proposes interventions to weaken such biases.     

When Age Matters: Differences in Facial Mimicry and Autonomic Responses to Peers' Emotions in Teenagers and Adults

Age-group membership effects on explicit emotional facial expressions recognition have been widely demonstrated. In this study we investigated whether Age-group membership could also affect implicit physiological responses, as facial mimicry and autonomic regulation, to observation of emotional facial expressions. To this aim, facial Electromyography (EMG) and Respiratory Sinus Arrhythmia (RSA) were recorded from teenager and adult participants during the observation of facial expressions performed by teenager and adult models. Results highlighted that teenagers exhibited greater facial EMG responses to peers'' facial expressions, whereas adults showed higher RSA-responses to adult facial expressions. The different physiological modalities through which young and adults respond to peers'' emotional expressions are likely to reflect two different ways to engage in social interactions with coetaneous. Findings confirmed that age is an important and powerful social feature that modulates interpersonal interactions by influencing low-level physiological responses.     

Leaders benefit followers in the collective movement of a social sawfly

The challenges of maintaining cohesion while making collective decisions in social or aggregating insects can result in the emergence of a leader or leaders. Larval aggregations of the steel-blue sawfly Perga affinis forage nocturnally, and some larvae lead the aggregation on foraging trips more often than expected by chance. We investigated the relationship between these leader and follower roles by comparing the weight and growth of individual larvae with different roles. Our observations reveal no significant difference between the growth of leaders and followers, suggesting that the role of leadership may not provide direct foraging benefits. However, by experimentally manipulating the social structure of larval aggregations, we found that individuals within aggregations that comprise a mixture of leaders and followers enjoy higher growth rates than those in aggregations comprising a single behavioural type. These data demonstrate, for the first time, individual benefits to maintaining a balance of leader and follower roles within larval aggregations, and highlight the importance of considering the perspectives of both leaders and followers when investigating the evolutionary significance of this behavioural variation within animal groups.     

Testosterone-mediated sex differences in the face shape during adolescence: subjective impressions and objective features

Sex identification of a face is essential for social cognition. Still, perceptual cues indicating the sex of a face, and mechanisms underlying their development, remain poorly understood. Previously, our group described objective age- and sex-related differences in faces of healthy male and female adolescents (12–18 years of age), as derived from magnetic resonance images (MRIs) of the adolescents' heads. In this study, we presented these adolescent faces to 60 female raters to determine which facial features most reliably predicted subjective sex identification. Identification accuracy correlated highly with specific MRI-derived facial features (e.g. broader forehead, chin, jaw, and nose). Facial features that most reliably cued male identity were associated with plasma levels of testosterone (above and beyond age). Perceptible sex differences in face shape are thus associated with specific facial features whose emergence may be, in part, driven by testosterone.     

Intergroup threat gates social attention in humans

Humans shift their attention to follow another person''s gaze direction, a phenomenon called gaze cueing. This study examined whether a particular social factor, intergroup threat, modulates gaze cueing. As expected, stronger responses of a particular in-group to a threatening out-group were observed when the in-group, conditioned to perceive threat from one of two out-groups, was presented with facial stimuli from the threatening and non-threatening out-groups. These results suggest that intergroup threat plays an important role in shaping social attention. Furthermore, larger gaze-cueing effects were found for threatening out-group faces than for in-group faces only at the 200 ms but not the 800 ms stimulus onset asynchrony (SOA); the specificity of the gaze-cueing effects at the short SOA suggests that threat cues modulate the involuntary component of gaze cueing.     

Conflict, sticks and carrots: war increases prosocial punishments and rewards

Unlike most species, humans cooperate extensively with group members who are not closely related to them, a pattern sustained in part by punishing non-cooperators and rewarding cooperators. Because internally cooperative groups prevail over less cooperative rival groups, it is thought that violent intergroup conflict played a key role in the evolution of human cooperation. Consequently, it is plausible that propensities to punish and reward will be elevated during intergroup conflict. Using experiments conducted before, during and after the 2006 Israel-Hezbollah war, we show that, during wartime, people are more willing to pay costs to punish non-cooperative group members and reward cooperative group members. Rather than simply increasing within-group solidarity, violent intergroup conflict thus elicits behaviours that, writ large, enhance cooperation within the group, thereby making victory more likely.     

Visual Cues of Object Properties Differentially Affect Anticipatory Planning of Digit Forces and Placement

Studies on anticipatory planning of object manipulation showed initial task failure (i.e., object roll) when visual object shape cues are incongruent with other visual cues, such as weight distribution/density (e.g., symmetrically shaped object with an asymmetrical density). This suggests that shape cues override density cues. However, these studies typically only measured forces, with digit placement constrained. Recent evidence suggests that when digit placement is unconstrained, subjects modulate digit forces and placement. Thus, unconstrained digit placement might be modulated on initial trials (since it is an explicit process), but not forces (since it is an implicit process). We tested whether shape and density cues would differentially influence anticipatory planning of digit placement and forces during initial trials of a two-digit object manipulation task. Furthermore, we tested whether shape cues would override density cues when cues are incongruent. Subjects grasped and lifted an object with the aim of preventing roll. In Experiment 1, the object was symmetrically shaped, but with asymmetrical density (incongruent cues). In Experiment 2, the object was asymmetrical in shape and density (congruent cues). In Experiment 3, the object was asymmetrically shaped, but with symmetrical density (incongruent cues). Results showed differential modulation of digit placement and forces (modulation of load force but not placement), but only when shape and density cues were congruent. When shape and density cues were incongruent, we found collinear digit placement and symmetrical force sharing. This suggests that congruent and incongruent shape and density cues differentially influence anticipatory planning of digit forces and placement. Furthermore, shape cues do not always override density cues. A continuum of visual cues, such as those alluding to shape and density, need to be integrated.     

Implicitly Priming the Social Brain: Failure to Find Neural Effects

Humans have a fundamental need for social relationships. Rejection from social groups is especially detrimental, rendering the ability to detect threats to social relationships and respond in adaptive ways critical. Indeed, previous research has shown that experiencing social rejection alters the processing of subsequent social cues in a variety of socially affiliative and avoidant ways. Because social perception and cognition occurs spontaneously and automatically, detecting threats to social relationships may occur without conscious awareness or control. Here, we investigated the automaticity of social threat detection by examining how implicit primes affect neural responses to social stimuli. However, despite using a well-established implicit priming paradigm and large sample size, we failed to find any evidence that implicit primes induced changes at the neural level. That implicit primes influence behavior has been demonstrated repeatedly and across a variety of domains, and our goal is not to question these effects. Rather, we offer the present study as cautionary evidence that such a paradigm may not be amenable to scanning in an fMRI environment.     

Warfare in an evolutionary perspective

The importance of warfare for human evolution is hotly debated in anthropology. Some authors hypothesize that warfare emerged at least 200,000–100,000 years BP, was frequent, and significantly shaped human social evolution. Other authors claim that warfare is a recent phenomenon, linked to the emergence of agriculture, and mostly explained by cultural rather than evolutionary forces. Here I highlight and critically evaluate six controversial points on the evolutionary bases of warfare. I argue that cultural and evolutionary explanations on the emergence of warfare are not alternative but analyze biological diversity at two distinct levels. An evolved propensity to act aggressively toward outgroup individuals may emerge irrespective of whether warfare appeared early/late during human evolution. Finally, I argue that lethal violence and aggression toward outgroup individuals are two linked but distinct phenomena, and that war and peace are complementary and should not always be treated as two mutually exclusive behavioral responses.     

Emergence of scale-free leadership structure in social recommender systems

The study of the organization of social networks is important for the understanding of opinion formation, rumor spreading, and the emergence of trends and fashion. This paper reports empirical analysis of networks extracted from four leading sites with social functionality (Delicious, Flickr, Twitter and YouTube) and shows that they all display a scale-free leadership structure. To reproduce this feature, we propose an adaptive network model driven by social recommending. Artificial agent-based simulations of this model highlight a "good get richer" mechanism where users with broad interests and good judgments are likely to become popular leaders for the others. Simulations also indicate that the studied social recommendation mechanism can gradually improve the user experience by adapting to tastes of its users. Finally we outline implications for real online resource-sharing systems.     

Visual Discrimination of Kin in Mandrills

Phenotype matching, a learning mechanism that evolved based on phenotypic cues shared among relatives, may provide animals with the ability to recognize unfamiliar kin. The generalization of this mechanism across animal species is debated, however, because appropriate tests are difficult to design due to possible confounding effects of familiarity. Hence, only a few studies have examined evidence for the existence of such a mechanism in natural populations. Here, we tested the phenotype matching hypothesis based on visual cues in a semi‐free‐ranging population of mandrills (Mandrillus sphinx) that contains individuals related to different degrees and where familiarity is controlled for. Using an experimental design based on the presentation of photographs, we show that mandrills discriminate unfamiliar relatives using facial cues alone. Our results build on earlier studies, showing that primates use phenotype matching to recognize and subsequently discriminate unfamiliar kin. We suggest that facial features along with other visual and non‐visual cues provide a proximate mechanism for kin selection to operate.     

Steeling Ourselves: Intragroup Communication while Anticipating Intergroup Contact Evokes Defensive Intergroup Perceptions

Two experiments investigated the role of intragroup communication in intergroup conflict (de-)escalation. Experiment 1 examined the effects of intragroup communication (vs. individual thought) and anticipated face-to-face intergroup contact (vs. no anticipated face-to-face intergroup contact). The group discussions of stigmatized group members who anticipated face-to-face intergroup contact revolved more around intergroup hostility. This boosted ingroup identification and increased social creativity but also led to steeling (a hardening of perceived intergroup relations). In Experiment 2, new participants listened to the taped group discussions. The discussions of groups anticipating face-to-face intergroup contact evoked more intergroup anxiety-related discomfort than discussions of groups not anticipating face-to-face intergroup encounters. Together, these results support the idea that steeling is a defensive reaction to prepare for an anxiety-arousing intergroup confrontation. Although steeling is also associated with positive consequences such as increased ingroup solidarity and social creativity, this hardened stance may be an obstacle to conflict de-escalation.     

Infanticide and social change in two groups of the hanuman langur,Presbytis entellus,at Jodhpur

Infanticide and social change in two neighbouring bisexual groups of the langur,Presbytis entellus, at Jodhpur (at the eastern edge of the Great Indian Desert), during a two-year period are described. Here the fluidity of leadership is more marked than in other primates. The change of leadership is sometimes associated with infanticide. Other features noted were: that neighbouring bisexual groups may temporarily fuse into one; and that intergroup presentations and copulations may occur.     

Facial cues to physical strength increase attractiveness but decrease aggressiveness assessments in male Maasai of Northern Tanzania

Male physical formidability may reflect capacities to provision and protect, resource holding potential, and social status. Handgrip strength (HGS) is a robust measure of overall muscular strength and function that correlates positively with ratings of male facial attractiveness and dominance. Here, we examine strength, attractiveness, and aggressiveness assessments as a function of facial cues to HGS in a sample of male Maasai of Northern Tanzania. Adult Maasai (56 women, 40 men) rated three strength-calibrated facial morphs of Maasai men. These morphs were constructed by performing a geometric morphometric shape regression on HGS using digital images of 54 men (20–29 years). Participants judged facial morphs calibrated to greater HGS higher on strength and attractiveness, but lower on aggressiveness. The accurate assessment of male Maasai physical strength from facial cues and the corresponding attractiveness assessments of strength cues are consistent with evolutionary predictions and previous research. The situation is less clear for the association of facial strength cues with the assessment of aggression. Future research should consider the possibility of a (feature-based) perceptual overgeneralization, especially in the interpretation of facial aggressiveness judgments, in addition to population-specific influences, and distinguish them from facial cues that indicate behavioral dispositions. Collectively, the findings of the present study corroborate the suggestion that the Maasai are sensitive to facial cues of strength and use these cues in social assessments.