Evolution & Human Behavior - Articles in Press

Why Women Have Sex - Corrected Proof

Jill M. Sundie — 2010-02-04

Sex is serious business. It significantly affects most adults' quality of life and well-being, and can cement or fracture the most intimate of social relationships. Sexual stimuli are so effective at capturing people's attention that in my field of marketing they are used daily to encourage people to purchase an array of products and services such as computing servers, submarine sandwiches, toilet paper, many other things seemingly unrelated to sex. A Google search of the well-known phrase “sex sells” returns over 693,000 hits.

A thin slice of violence: distinguishing violent from nonviolent sex offenders at a glance - Corrected Proof

Tyler F. Stillman, Jon K. Maner, Roy F. Baumeister — 2010-02-04

Abstract: A growing body of literature in evolutionary psychology suggests that person perception processes are adaptively tuned. The current investigation tested the hypothesis that people would be able to detect a propensity for violence in other people, based only on a brief glance at their face. Participants estimated the propensity for violence in 87 registered sex offenders after seeing photos of them for 2 s each. Estimated likelihood of violence was significantly related to actual violent history, suggesting that violent tendencies can be accurately inferred from a brief look at a person's face. Cues indicative of high masculinity and high levels of male sex hormones (heavy brow, general facial masculinity, high physical strength, younger age) were related to accurate judgments. Other cues such as facial emotion and good grooming were not associated with an actual history of violence, but nevertheless correlated with raters' judgments. Although there were no sex differences in accuracy, on average women thought targets were more violent than men did. Findings speak to the accuracy and efficiency with which people can detect potential threats to physical well-being.

Glimpses of Creatures in Their Physical Worlds - Corrected Proof

Peter DeScioli — 2010-02-04

Glimpses of Creatures in Their Physical Worlds is a heart-pounding, heat-conducting, power-amplifying whirlwind tour through the mechanical and thermal worlds of Earth's living things. The journey has something for everyone: the thrills of explosively launched projectiles, the chills of supercooling polar fish, the rise of birds soaring on an ascending torus of ground-heated air. Along the way, there are insights into the functional analysis of biological systems, relevant not only to researchers in biomechanics but also to the broad community of scientists seeking to understand the workings of life's devices.

Cooperative pastoral production — the importance of kinship - Corrected Proof

Marius Warg Næss, Bård-Jørgen Bårdsen, Per Fauchald, Torkild Tveraa — 2010-02-04

Abstract: While there is a general assumption that labour has a positive effect on pastoral production, studies that have quantified this relationship have been characterized by ambiguous results. This is most likely related to the fact that possible cooperative pastoral production has been little explored in the literature, although it is well documented that nomadic pastoralist households share and exchange labour in so-called cooperative herding groups. Consequently, this study aims at investigating possible cooperative labour-related effects on production among Saami reindeer herders in Norway by using kinship relations as a proxy for cooperation. This study found that cooperative labour investment is important for Saami reindeer herders, but that the effect of kinship and labour needs to be understood in relation to each other. When assessing the effect of labour and kinship simultaneously, both labour and genealogical relationship had positive effects on herd size. We also found a positive interaction between kinship and labour suggesting that high levels of relatedness coupled with a large potential labour pool had an increasingly positive effect on herd size.

Giving it all away: altruism and answers to the Wason selection task - Corrected Proof

Laurence Fiddick, Nicole Erlich — 2009-12-11

Abstract: The Wason selection task, a standard test of conditional reasoning, has featured prominently in experimental studies of cognitive adaptations for cooperation. The most prominent of these is Cosmides' investigations of cheater detection on social contract versions of the Wason selection task [Cognition 31 (1989) 187–276]. Subsequent to Cosmides' initial investigations, several researchers [Evol Hum Behav 21 (200) 25–37; Manage Decis Econ 19 (1998) 467–480; J Genet Psychol 163 (2002) 425–444; Evol Hum Behav 27 (2006) 366–380] have argued that people also are competent at detecting altruism on the Wason selection task, suggesting that there is nothing privileged about the detection of cheaters. However, an analysis of the selection tasks on which these claims are based suggests that participants may have solved these altruism-detection tasks correctly because the scenarios explicitly or implicitly provide the answer to the task in the scenario [Evol Hum Behav 21 (200) 25–37; Manage Decis Econ 19 (1998) 467–480; J Genet Psychol 163 (2002) 425–444], or due to confounds in the cheater-detection tasks leading to the (misleading) appearance of enhanced altruist-detection performance [Evol Hum Behav 27 (2006) 366–380]. We tested our conjecture by giving participants selection tasks with and without the answer embedded in the scenario. Performance dropped significantly on the altruism-detection tasks when the embedded answers were removed, whereas performance on cheater-detection versions was unaffected by the manipulation. A reanalysis of the findings of Oda et al. suggested that participants performed significantly worse on their altruism-detection problems than their cheater-detection problems — a finding that we replicate after removing confounds from the cheater-detection tasks of Oda et al. The results reaffirm the specificity of cheater-detection.

Corrected Proof

Terence C. Burnham — 2009-12-09

In Spent, Geoff Miller brings an evolutionary perspective to consumer behavior in modern industrialized societies. The puzzle is the empty and energetic pursuit of materialistic goals. Why do we work so hard to buy goods and services that rarely produce lasting satisfaction?

Blind men prefer a low waist-to-hip ratio - Corrected Proof

Johan C. Karremans, Willem E. Frankenhuis, Sander Arons — 2009-12-09

Abstract: Previous studies suggest that men in Western societies are attracted to low female waist-to-hip ratios (WHR). Several explanations of this preference rely on the importance of visual input for the development of the preference, including explanations stressing the role of visual media. We report evidence showing that congenitally blind men, without previous visual experience, exhibit a preference for low female WHRs when assessing female body shapes through touch, as do their sighted counterparts. This finding shows that a preference for low WHR can develop in the complete absence of visual input and, hence, that such input is not necessary for the preference to develop. However, the strength of the preference was greater for the sighted than the blind men, suggesting that visual input might play a role in reinforcing the preference. These results have implications for debates concerning the evolutionary and developmental origins of human mate preferences, in particular, regarding the role of visual media in shaping such preferences.

Altruism toward in-group members as a reputation mechanism - Corrected Proof

Nobuhiro Mifune, Hirofumi Hashimoto, Toshio Yamagishi — 2009-12-02

Abstract: To test the hypothesis that sensitivity to monitoring drives people to act altruistically toward members of their own community, two experiments investigated whether an eye-like painting promotes altruism toward in-group members, but not toward out-group members. Participants played the role of dictator in a dictator game with another participant (a recipient) who was from the minimal in-group or out-group. Participants knew whether their recipient was an in-group member or an out-group member, but were informed that their recipient did not know the group membership of the dictator. In-group favoritism occurred only when participants were facing a computer desktop which displayed a painting of eyes, but did not occur in the absence of eyes. These findings demonstrate that the eye painting displayed on the participant's computer screen worked as a cue for monitoring and thus enhanced the participant's altruistic behavior.

Male traits associated with attractiveness in Conambo, Ecuador - Corrected Proof

Michelle Escasa, Peter B. Gray, John Q. Patton — 2009-12-02

Abstract: This study investigated male attractiveness rankings in a small-scale Amazonian society. In the rural community of Conambo, Ecuador, men and women practice self-sufficient horticulture, men hunt, and, traditionally, men have experienced a high rate of mortality due to homicide. We tested whether male attractiveness rankings would be related to male age, warriorship, hunting ability, status, coalitional affiliation, and female age. Twenty-five women aged between 14 and 78 years ranked photographs of 29 local men aged between 16 and 74 years for attractiveness in addition to warriorship, hunting ability, and status. Results revealed that male age was negatively correlated (r=−.683, p=.01) with female rankings of male attractiveness. Warriorship (r=.517, p=.005), status (r=.489, p=.008), and hunting ability (r=.577, p=.001) were found to be positively correlated with attractiveness, after controlling for age. Additionally, females showed a bias for males in their in-group when ranking attractiveness (one-sample t test: T29=16.727, p<.001). Attention is given to male age and coalitional affiliation as factors important in attractiveness rankings; warriorship and hunting ability also serve as ecologically salient features of male social worth. These findings contribute to a broader understanding of human attractiveness research by adding a new case study to the literature that documents previously unreported findings from a cultural context that is significantly different from the standard university-level student sample.

Tattoo and piercing as signals of biological quality - Corrected Proof

Slawomir Koziel, Weronika Kretschmer, Boguslaw Pawlowski — 2009-12-02

Abstract: Tattoos and non-conventional piercings are used in many societies. There are several social reasons for which people use these forms of body decorations (e.g., marking social status or signaling membership within a subculture). However, it is interesting why only some people within a group that uses body decoration as a badge of membership decide upon such decorations. Since both tattoos and piercings can present health risks (e.g., due to blood-borne disease transmission risk), we postulate that people who decide to have such a body decoration might have relatively higher biological quality and that tattoos/piercings can be an honest signal of genetic quality. The possible opposite hypothesis is the “attractiveness increase hypothesis,” according to which people use body decorations to increase their own physical attractiveness or to hide some shortcomings in their appearance (e.g., low body symmetry). To test these hypotheses, we compared body fluctuating asymmetry, which is considered a good measure of developmental stability, between individuals wearing tattoos and/or non-conventional piercings (n=116) and a control group (without such body decorations) (n=86). We found that majority of the absolute and relative fluctuating asymmetry indices had significantly lower values in individuals with tattoos/piercings than in the control group. This effect was strongly driven by males. Higher body symmetry of the men having tattoo or piercing indicates that this type of body decoration in the western society can be related to the honest signal of biological quality only for men. We did not find support for the “attractiveness increase hypothesis” for either sex.

Biased face recognition in the Faith Game - Corrected Proof

Ryo Oda, Shun Nakajima — 2009-11-16

Abstract: Several studies have indicated that people are able to memorize the face of a cheater more accurately than that of a noncheater, but some contradictory findings have also been reported. Because most previous studies focused on memory for the faces of cheaters who break social contracts, the consequence for the subjects of their cheating was unclear. In our study, participants were asked to decide whether they trusted persons depicted in photographs to give them money using two sessions of the Faith Game. The participants tended to not increase their trust in the individuals, depicted in photographs, who had altruistically given money to them previously. However, participants recognized nonaltruists who had not shared money and, during the second session, rescinded the trust that they had previously placed in them. This suggests that bias in face recognition is not restricted to the recognition level, as previous studies have suggested, but also operates at the behavioral level and functions to facilitate the avoidance of persons who have caused some disadvantage in a previous interaction, rather than to facilitate new relationships with altruists by enhancing recognition of their faces.

Conservatism in laboratory microsocieties: unpredictable payoffs accentuate group-specific traditions - Corrected Proof

Christine A. Caldwell, Ailsa E. Millen — 2009-11-09

Abstract: Theoretical work predicts that individuals should strategically increase their reliance on social learning when individual learning would be costly or risky, or when the payoffs for individually learned behaviors are uncertain. Using a method known to elicit cumulative cultural evolution in the laboratory, we investigated the degree of within-group similarity, and between-group variation, in design choices made by participants under conditions of varying uncertainty about the likely effectiveness of those designs. Participants were required to build a tower from spaghetti and modeling clay, their goal being to build the tower as high as possible. In one condition, towers were measured immediately on completion and, therefore, participants were able to judge the success of their design during building. In the other condition, participants' towers were measured 5 min after completion, following a deliberate attempt to test the tower's stability, making it harder for participants to judge whether an innovative solution was liable to result in a good score on the final measurement. Cultural peculiarity (i.e., the extent to which a design could be identified as belonging to a particular chain) was stronger in the delayed measure condition, indicating that participants were placing greater reliance on social learning. Furthermore, in this condition, there was only very weak evidence of successive improvement in performance over learner generations, whereas in the immediate measure condition there was a clear effect of steadily increasing scores on the goal measurement. Increasing the risk associated with learning for oneself may favor the development of arbitrary traditions.

Emotional expressivity as a signal of cooperation - Corrected Proof

Joanna Schug, David Matsumoto, Yutaka Horita, Toshio Yamagishi, Kemberlee Bonnet — 2009-11-09

Abstract: Previous research has suggested that the spontaneous display of positive emotion may be a reliable signal of cooperative tendency in humans. Consistent with this proposition, several studies have found that self-reported cooperators indeed display higher levels of positive emotions than non-cooperators. In this study, we defined cooperators and non-cooperators in terms of their behavior as the proposer in an ultimatum game, and video-taped their facial expressions as they faced unfair offers as a responder. A detailed analysis of the facial expressions displayed by participants revealed that cooperators displayed greater amounts of emotional expressions, not limited to positive emotional expression, when responding to unfair offers in the ultimatum game. These results suggest that cooperators may be more emotionally expressive than non-cooperators. We speculate that emotional expressivity can be a more reliable signal of cooperativeness than the display of positive emotion alone.

Altruism towards strangers in need: costly signaling in an industrial society - Corrected Proof

Tamas Bereczkei, Bela Birkas, Zsuzsanna Kerekes — 2009-10-23

Abstract: In the present study, the costly signaling theory (CST) is used to examine the effect of an offer of charity on social recognition. On behalf of a charitable organization, 186 students enrolled in 16 different courses were asked to offer support to unfamiliar persons in need. In accordance with our predictions, the results show that significantly more subjects are willing to give assistance if they make charity offers in the presence of their group members than when the offers are made in secret. In accordance with CST—but not with the prevailing explanations in social psychology—the likelihood of charity service was strongly influenced by the expected cost of altruistic behavior. Publicly demonstrated altruistic intentions yielded long-term benefits: Subjects who were willing to participate in a particular charity activity gained significantly higher sociometry scores (as a sign of social recognition) than did others. The cost of volunteerism correlated with social recognition in the case of a charity act judged as the most expensive (giving assistance to mentally retarded children), but not for the other categories of charity offer. Our results suggest that public generosity towards strangers as a costly signal may convey reliable information about subjects' personality traits, such as cooperativeness, but our data do not support the hypothesis that the signaling mechanism is related to sexual selection and mate choice.

Corrected Proof

Timothy Ketelaar — 2009-10-09

“Are these the Nazis, Walter?”“No, Donny, these men are nihilists, there's nothing to be afraid of.”Dialogue from The Big Lebowski,Generation X and, even more so, the generation following it (those born 1984–2000) have grown up an extremely nihilistic generation. I do not mean nihilistic in the way The Big Lebowski means it (where they care about nothing), but instead in what I believe to be the mantra of nihilism: de omnibus dubitandum (“everything is to be doubted”). Many people associate this saying with Descartes, but I believe it is Nietzsche that understood the real impact of the term.Blog posting from the website “The Christian Watershed”

It's funny because we think it's true: laughter is augmented by implicit preferences - Corrected Proof

Robert Lynch — 2009-10-05

Abstract: This study tests the folk psychological belief that we find things funny because we think they are true. Specifically, it addresses the relationship between implicit preferences and laughter. Fifty-nine undergraduate Rutgers University students (33 females and 26 males) from ethnically diverse backgrounds were videotaped while watching a white stand-up comedian for 30 min. Positive emotional expression associated with laughter was later scored using the facial action coding system (FACS). Computer-timed Implicit Association Tests (IATs) were used to measure a subject's implicit preferences for traditional gender roles and racial preferences (blacks vs. whites). Results show that participants laughed more in response to jokes that matched their implicit preferences (e.g., those with stronger implicit preferences for whites laughed more at racially charged material). Implications for the evolution of humor, and laughter as a hard-to-fake signal of preferences, are discussed.

Corrected Proof

Catherine Salmon — 2009-09-22

It seems these days that female sexuality is one of the hot topics, whether you are a psychologist, biologist, sex researcher, anthropologist, sociologist or feminist. A plethora of books (both academic and popular press) have been published from The Secrets of Female Sexuality: Unapologetic Brutally Honest Truth About Sex That Women Secretly Wish You Knew But Can't Tell You (2007) by David Shade to The Case of The Female Orgasm: Bias in the Science of Evolution (2006) by Elizabeth Lloyd to the soon-to-be-published Why Women Have Sex: Understanding Sexual Motivations From Adventure to Revenge (And Everything in Between) (2009) by Cindy Meston and David Buss.

Hormonal responses differ when playing violent video games against an ingroup and outgroup - Corrected Proof

Jonathan Oxford, Davidé Ponzi, David C. Geary — 2009-09-16

Abstract: For 14 teams of three young men, salivary testosterone and cortisol were assessed twice before and twice after competing in within-group and between-group video games that simulated violent male–male competition. Men who contributed the most to their teams' between-group victory showed testosterone increases immediately after the competition, but only if this competition was played before the within-group tournament. High-scoring men on losing teams did not show this immediate effect, but they did show a delayed increase in testosterone. In contrast, high-ranking men tended to have lower testosterone and higher cortisol during within-group tournaments. The results are consistent with the hypothesis that men's competitive testosterone response varies across ingroup and outgroup competitions and is muted during the former. The testosterone response during the between-group competition also suggests that violent multiplayer video games may be appealing to young men because they simulate male–male coalitional competition.

Cooperation in humans: competition between groups and proximate emotions - Corrected Proof

Maxwell N. Burton-Chellew, Adin Ross-Gillespie, Stuart A. West — 2009-09-16

Abstract: Understanding the ultimate and proximate mechanisms that favour cooperation remains one of the greatest challenges in the biological and social sciences. A number of theoretical studies have suggested that competition between groups may have played a key role in the evolution of cooperation within human societies, and similar ideas have been discussed for other organisms, especially cooperative breeding vertebrates. However, there is a relative lack of empirical work testing these ideas. Our experiment found, in public goods games with humans, that when groups competed with other groups for financial rewards, individuals made larger contributions within their own groups. In such situations, participants were more likely to regard their group mates as collaborators rather than competitors. Variation in contribution among individuals, either with or without intergroup competition, was positively correlated with individuals' propensity to regard group mates as collaborators. We found that the levels of both guilt and anger individuals experienced were a function of their own contributions and those of their group mates. Overall, our results are consistent with the idea that the level of cooperation can be influenced by proximate emotions, which vary with the degree of intergroup competition.

Currency value moderates equity preference among young children - Corrected Proof

Peter R. Blake, David G. Rand — 2009-09-10

Abstract: Cooperative behavior depends in part on a preference for equitable outcomes. Recent research in behavioral economics assesses variables that influence adult concerns for equity, but few studies to date investigate the emergence of equitable behavior in children using similar economic games. We tested 288 3- to 6-year olds in an anonymous Dictator Game to assess how the value of the currency used affects equity preferences in children. To manipulate value, children played the game with their most or least favorite stickers. At all ages, we found a strong value effect with children donating more of their least favorite stickers than their favorite stickers. We also found a dramatic increase with age in the percentage of children who were prosocial (i.e. donated at least one sticker). However, children who were prosocial tended to give the same proportion of stickers at all ages – about half of their least favorite stickers and 40% of their favorite stickers. These findings highlight the influence of resource value on children's preference for equity, and provide evidence for two different processes underlying altruistic giving: the decision to donate at all and the decision about how much to donate.

Not only states but traits — Humans can identify permanent altruistic dispositions in 20 s - Corrected Proof

Detlef Fetchenhauer, Ton Groothuis, Julia Pradel — 2009-09-09

Abstract: Humans behave altruistically in one-shot interactions under total anonymity. In search of explanations for such behavior, it has been argued that at least some individuals have a general tendency to behave altruistically independent of profitability. In fact, a stable altruistic trait would be adaptive if it were recognizable. Then, altruists could choose each other in order to retain benefits through mutual cooperation. Previous research has shown that individuals can predict the degree of altruistic behavior of strangers by reading signs of emotions evoked in significant social decisions. However, the identification of benevolent emotional states is no guarantee of the existence of permanent altruistic traits, though permanent traits are the preferable criterion for selection of good interaction partners. In this study, we tested whether individuals are able to identify altruistic traits. Judges watched 20-s silent video clips of unacquainted target persons and were asked to estimate the behavior of these target persons in a money-sharing task. As the videotapes of the target persons had been recorded in a setting unrelated to altruistic behavior, the judges could not base their estimates on situational cues related to the money-sharing task but instead had to draw on stable signals of altruism. Estimates were significantly better than chance, indicating that individuals can identify permanent altruistic traits in others. As this mechanism raises opportunities for selective interactions between altruists, our findings are discussed with respect to their relevance for explaining the evolution of altruism through assortment.

WITHDRAWN: Audience effects on moralistic punishment☆ - Corrected Proof

Robert Kurzban, Peter DeScioli, Erin O'Brien — 2006-10-10

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.