Michael E. Price

Punitive sentiment as an anti-free rider psychological device

Those who contribute to a public good sometimes experience punitive sentiments toward others. But is the system that produces these sentiments an adaptation and, if so, which collective action problem was it designed to solve? Prior results from experimental economics show that acts of free riding are sometimes punished, that punishment deters free riding, and that the risk or actuality of punishment recruits higher levels of cooperation in a joint effort. This suggests that one function of punitive sentiments could be to recruit labor for collective actions. However, adaptations designed to cause participation in collective actions could not have evolved unless there were some mechanism that protected those who participated from having lower fitness than nonparticipating free riders. Therefore, a second possible function of punishment could be to eliminate or reverse fitness differentials that favor free rider designs over participant designs. To map the computational structure of this motivational adaptation (and hence identify its specific function) requires data that relate an individual’s circumstances to his or her desire to punish. Herein, we report such data. The results indicate that the computational system that regulates one’s level of punitive sentiment in collective action contexts is functionally specialized for removing the fitness advantage enjoyed by free riders rather than for labor recruitment or other functions. Results also support the hypothesis that a separate pro-reward motivational system exists that appears designed to handle the problem of labor recruitment. Rational choice counterexplanations for punitive sentiments were considered but eliminated on the basis of the evidence. D 2002 Elsevier Science Inc. All rights reserved.

Fluctuating asymmetry and preferences for sex-typical bodily characteristics

Body size and shape seem to have been sexually selected in a variety of species, including humans, but little is known about what attractive bodies signal about underlying genotypic or phenotypic quality. A widely used indicator of phenotypic quality in evolutionary analyses is degree of symmetry (i.e., fluctuating asymmetry, FA) because it is a marker of developmental stability, which is defined as an organisms ability to develop toward an adaptive end-point despite perturbations during its ontogeny. Here we sought to establish whether attractive bodies signal low FA to observers, and, if so, which aspects of attractive bodies are most predictive of lower FA. We used a 3D optical body scanner to measure FA and to isolate size and shape characteristics in a sample of 77 individuals (40 males and 37 females). From the 3D body scan data, 360° videos were created that separated body shape from other aspects of visual appearance (e.g., skin color and facial features). These videos then were presented to 87 evaluators for attractiveness ratings. We found strong negative correlations between FA and bodily attractiveness in both sexes. Further, sex-typical body size and shape characteristics were rated as attractive and correlated negatively with FA. Finally, geometric morphometric analysis of joint configurations revealed that sex-typical joint configurations were associated with both perceived attractiveness and lower FA for male but not for female bodies. In sum, body size and shape seem to show evidence of sexual selection and indicate important information about the phenotypic quality of individuals.

PRO-COMMUNITY ALTRUISM AND SOCIAL STATUS IN A SHUAR VILLAGE

Reciprocity theory (RT) and costly signaling theory (CST) provide different explanations for the high status of pro-community altruists: RT proposes that altruists are positively and negatively sanctioned by others, whereas CST proposes that altruists are attractive to others. Only RT, however, is beset by first- and higher-order free rider problems, which must be solved in order for RT to explain status allocations. In this paper, several solutions to RT’s free rider problems are proposed, and data about status allocations to Ecuadorian Shuar pro-community altruists are analyzed in light of RT and CST. These data confirm that perceived pro-community altruists are indeed high status and suggest that (1) community residents skillfully monitor the altruism of coresidents, (2) residents who engage in opportunities to broadcast desirable qualities are high status only to the extent that they are considered altruistic, and (3) individuals who sanction coresidents based on coresidents’ contributions to the community are themselves relatively high status. To a greater extent than CST, RT straightforwardly predicts all of these results.

The evolution of leader–follower reciprocity: the theory of service-for-prestige

We describe the service-for-prestige theory of leadership, which proposes that voluntary leader–follower relations evolved in humans via a process of reciprocal exchange that generated adaptive benefits for both leaders and followers. We propose that although leader–follower relations first emerged in the human lineage to solve problems related to information sharing and social coordination, they ultimately evolved into exchange relationships whereby followers could compensate leaders for services which would otherwise have been prohibitively costly for leaders to provide. In this exchange, leaders incur costs to provide followers with public goods, and in return, followers incur costs to provide leaders with prestige (and associated fitness benefits). Because whole groups of followers tend to gain from leader-provided public goods, and because prestige is costly for followers to produce, the provisioning of prestige to leaders requires solutions to the “free rider” problem of disrespectful followers (who benefit from leader services without sharing the costs of producing prestige). Thus service-for-prestige makes the unique prediction that disrespectful followers of beneficial leaders will be targeted by other followers for punitive sentiment and/or social exclusion. Leader–follower relations should be more reciprocal and mutually beneficial when leaders and followers have more equal social bargaining power. However, as leaders gain more relative power, and their high status becomes less dependent on their willingness to pay the costs of benefitting followers, service-for-prestige predicts that leader–follower relations will become based more on leaders’ ability to dominate and exploit rather than benefit followers. We review evidential support for a set of predictions made by service-for-prestige, and discuss how service-for-prestige relates to social neuroscience research on leadership.

Body shape preferences: associations with rater body shape and sociosexuality.

There is accumulating evidence of condition-dependent mate choice in many species, that is, individual preferences varying in strength according to the condition of the chooser. In humans, for example, people with more attractive faces/bodies, and who are higher in sociosexuality, exhibit stronger preferences for attractive traits in opposite-sex faces/bodies. However, previous studies have tended to use only relatively simple, isolated measures of rater attractiveness. Here we use 3D body scanning technology to examine associations between strength of rater preferences for attractive traits in opposite-sex bodies, and raters’ body shape, self-perceived attractiveness, and sociosexuality. For 118 raters and 80 stimuli models, we used a 3D scanner to extract body measurements associated with attractiveness (male waist-chest ratio [WCR], female waist-hip ratio [WHR], and volume-height index [VHI] in both sexes) and also measured rater self-perceived attractiveness and sociosexuality. As expected, WHR and VHI were important predictors of female body attractiveness, while WCR and VHI were important predictors of male body attractiveness. Results indicated that male rater sociosexuality scores were positively associated with strength of preference for attractive (low) VHI and attractive (low) WHR in female bodies. Moreover, male rater self-perceived attractiveness was positively associated with strength of preference for low VHI in female bodies. The only evidence of condition-dependent preferences in females was a positive association between attractive VHI in female raters and preferences for attractive (low) WCR in male bodies. No other significant associations were observed in either sex between aspects of rater body shape and strength of preferences for attractive opposite-sex body traits. These results suggest that among male raters, rater self-perceived attractiveness and sociosexuality are important predictors of preference strength for attractive opposite-sex body shapes, and that rater body traits –with the exception of VHI in female raters– may not be good predictors of these preferences in either sex.

Revisiting ''The Evolution of Reciprocity in Sizable Groups'': Continuous reciprocity in the repeated n-person prisoner's dilemma

For many years in evolutionary science, the consensus view has been that while reciprocal altruism can evolve in dyadic interactions, it is unlikely to evolve in sizable groups. This view had been based on studies which have assumed cooperation to be discrete rather than continuous (i.e., individuals can either fully cooperate or else fully defect, but they cannot continuously vary their level of cooperation). In real world cooperation, however, cooperation is often continuous. In this paper, we re-examine the evolution of reciprocity in sizable groups by presenting a model of the n-person prisoners dilemma that assumes continuous rather than discrete cooperation. This model shows that continuous reciprocity has a dramatically wider basin of attraction than discrete reciprocity, and that this basins size increases with efficiency of cooperation (marginal per capita return). Further, we find that assortative interaction interacts synergistically with continuous reciprocity to a much greater extent than it does with discrete reciprocity. These results suggest that previous models may have underestimated reciprocitys adaptiveness in groups. However, we also find that the invasion of continuous reciprocators into a population of unconditional defectors becomes realistic only within a narrow parameter space in which the efficiency of cooperation is close to its maximum bound. Therefore our model suggests that continuous reciprocity can evolve in large groups more easily than discrete reciprocity only under unusual circumstances.

Why is low waist-to-chest ratio attractive in males? The mediating roles of perceived dominance, fitness, and protection ability

Past research suggests that a lower waist-to-chest ratio (WCR) in men (i.e., narrower waist and broader chest) is viewed as attractive by women. However, little work has directly examined why low WCRs are preferred. The current work merged insights from theory and past research to develop a model examining perceived dominance, fitness, and protection ability as mediators of to WCR-attractiveness relationship. These mediators and their link to both short-term (sexual) and long-term (relational) attractiveness were simultaneously tested by having 151 women rate one of 15 avatars, created from 3D body scans. Men with lower WCR were perceived as more physically dominant, physically fit, and better able to protect loved ones; these characteristics differentially mediated the effect of WCR on short-term, long-term, and general attractiveness ratings. Greater understanding of the judgments women form regarding WCR may yield insights into motivations by men to manipulate their body image.

The Adaptationist Theory of Cooperation in Groups: Evolutionary Predictions for Organizational Cooperation

Managers could more effectively promote cooperation within their organizations if they had greater understanding of how evolution designed people to cooperate. Here we present a theory of group cooperation – the Adaptationist Theory of Cooperation in Groups (ATCG) – that is primarily an effort to pull together the scattered findings of a large number of evolution-minded researchers, and to integrate these findings into a single coherent theory. We present ATCG in three main sections: first, we discuss the basic premise that group cooperation evolved because it allowed individuals to acquire personal fitness benefits from acting in synergy with others; second, we examine the cooperative strategy that most often prevails in successful groups, “reciprocal altruism”, and the free rider problem that constantly threatens it; and third, we explore how cooperative behavior is affected by differences (a) among individuals, (b) between the sexes, and (c) among different kinds of resources that a group may share. Throughout all of these sections, we suggest ways in which ATCG’s predictions could be usefully applied in real organizations. We conclude that while ATCG is consistent in some regards with existing theories from organizational behaviour, its individual-level adaptationist perspective allows it to make a variety of novel predictions.

Bodily Attractiveness and Egalitarianism are Negatively Related in Males

Ancestrally, relatively attractive individuals and relatively formidable males may have had reduced incentives to be egalitarian (i.e., to act in accordance with norms promoting social equality). If selection calibrated ones egalitarianism to ones attractiveness/formidability, then such people may exhibit reduced egalitarianism (“observed egalitarianism”) and be perceived by others as less egalitarian (“perceived egalitarianism”) in modern environments. To investigate, we created 3D body models of 125 participants to use both as a source of anthropometric measurements and as stimuli to obtain ratings of bodily attractiveness and perceived egalitarianism. We also measured observed egalitarianism (via an economic “dictator” game) and indices of political egalitarianism (preference for socialism over capitalism) and “equity sensitivity.” Results indicated higher egalitarianism levels in women than in men, and moderate-to-strong negative relationships between (a) attractiveness and observed egalitarianism among men, (b) attractiveness and perceived egalitarianism among both sexes, and (c) formidability and perceived egalitarianism among men. We did not find support for two previously-reported findings: that observed egalitarianism and formidability are negatively related in men, and that wealth and formidability interact to explain variance in male egalitarianism. However, this lack of support may have been due to differences in variable measurement between our study and previous studies.

Extraction of bodily features for gait recognition and gait attractiveness evaluation

Although there has been much previous research on which bodily features are most important in gait analysis, the questions of which features should be extracted from gait, and why these features in particular should be extracted, have not been convincingly answered. The primary goal of the study reported here was to take an analytical approach to answering these questions, in the context of identifying the features that are most important for gait recognition and gait attractiveness evaluation. Using precise 3D gait motion data obtained from motion capture, we analyzed the relative motions from different body segments to a root marker (located on the lower back) of 30 males by the fixed root method, and compared them with the original motions without fixing root. Some particular features were obtained by principal component analysis (PCA). The left lower arm, lower legs and hips were identified as important features for gait recognition. For gait attractiveness evaluation, the lower legs were recognized as important features.