Why and under what conditions are individuals altruistic to family and friends in their social networks? Evolutionary psychology suggests that such behaviour is primarily the product of adaptations for kin- and reciprocal altruism, dependent on the degree of genetic relatedness and exchange of benefits, respectively. For this reason, individuals are expected to be more altruistic to family members than to friends: whereas family members can be the recipients of kin and reciprocal altruism, friends can be the recipients of reciprocal altruism (...) only. However, there is a question about how the effect of kinship is implemented at the proximate psychological level. One possibility is that kinship contributes to some general measure of relationship quality (such as ‘emotional closeness’), which in turn explains altruism. Another possibility is that the effect of kinship is independent of relationship quality. The present study tests between these two possibilities. Participants (N= 111) completed a self-report questionnaire about their willingness to be altruistic, and their emotional closeness, to 12 family members and friends at different positions in their extended social networks. As expected, altruism was greater for family than friends, and greater for more central layers of the network. Crucially, the results showed that kinship made a significant unique contribution to altruism, even when controlling for the effects of emotional closeness. Thus, participants were more altruistic towards kin than would be expected if altruism was dependent on emotional closeness alone – a phenomenon we label a ‘kinship premium’. These results have implications for the ongoing debate about the extent to which kin relations and friendships are distinct kinds of social relationships, and how to measure the ‘strength of ties’ in social networks. (shrink)

Cooperation requires that individuals are able to identify, and preferentially associate with, others who have compatible preferences and the shared background knowledge needed to solve interpersonal coordination problems. The present study investigates the nature of such similarity within social networks, asking: What do friends have in common? And what is the relationship between similarity and altruism? The results show that similarity declines with frequency of contact; similarity in general is a significant predictor of altruism and emotional closeness; and, specifically, sharing (...) a sense of humor, hobbies and interests, moral beliefs, and being from the same area are the best predictors. These results shed light on the structure of relationships within networks and provide a possible checklist for predicting attitudes toward strangers, and in-group identification. (shrink)

When the social sciences parted company from evolutionary biology almost exactly a century ago, they did so at a time when evolutionary biology was still very much in its infancy and many key issues were unresolved. As a result, the social sciences took away with them an understanding of evolution that was in fact based on 18th- rather than 19th-century biology. I argue that contemporary evolutionary thinking has much more to offer the social sciences than most people have assumed. Contemporary (...) evolutionary research on human behaviour focuses on two main issues at the micro-social scale: understanding the trade-offs in individual decision-making and understanding the cognitive constraints that limit flexibility of decisions. I offer examples of both of these approaches. Finally, I consider the broader question of the macro-social scale. (shrink)

Drama, at least according to the Aristotelian view, is effective inasmuch as it successfully mirrors real aspects of human behavior. This leads to the hypothesis that successful dramas will portray fictional social networks that have the same properties as those typical of human beings across ages and cultures. We outline a methodology for investigating this hypothesis and use it to examine ten of Shakespeare’s plays. The cliques and groups portrayed in the plays correspond closely to those which have been observed (...) in spontaneous human interaction, including in hunter-gatherer societies, and the networks of the plays exhibit “small world” properties of the type which have been observed in many human-made and natural systems. (shrink)

The original book chapter does not have an abstract. However, I have written an abstract for this repository: Religious life encompasses a wide diversity of situations for which the emotional tone is on a continuum from extreme euphoria to extreme dysphoria. In this book chapter, we propose the novel hypothesis that euphoria and dysphoria have distinctly separate functional consequences for religious evolution and survivability. This is due to the differential cognitive states that are created in euphoric and dysphoric situations. Based (...) on readings from religious studies and cognitive psychology, we propose that euphoria in religion is conducive to social bonding and situations needing lateral thinking and creativity; whereas dysphoria in religion is conducive to situations where precision and analogical reasoning are necessary. (shrink)

Hormonal changes associated with the human menstrual cycle have been previously found to affect female mate preference, whereby women in the late follicular phase of their cycle (i.e., at higher risk of conception) prefer males displaying putative signals of underlying genetic fitness. Past research also suggests that romantic kissing is utilized in human mating contexts to assess potential mating partners. The current study examined whether women in their late follicular cycle phase place greater value on kissing at times when it (...) might help serve mate assessment functions. Using an international online questionnaire, results showed that women in the follicular phase of their menstrual cycle felt that kissing was more important at initial stages of a relationship than women in the luteal phase of their cycle. Furthermore, it was found that estimated progesterone levels were a significant negative predictor for these ratings. (shrink)