Ravens remember the nature of a single reciprocal interaction sequence over 2 days and even after a month

To explain reciprocity, direct or indirect, several proximate mechanisms have been proposed, yet little attention has been given to the specific underlying cognitive mechanisms. Regardless of what proximate rules underlie reciprocity, some kind of memory would be paramount. Corvids in general, and ravens, Corvus corax, specifically, have been shown to possess an array of sophisticated cognitive mechanisms involved in memory. In this study, we tested the memory of nine ravens in an exchange paradigm where they could exchange a low-quality for a high-quality food item. Specifically, we tested whether they remembered who was a reliable ‘fair’ experimenter and who would not reliably exchange (the ‘unfair’ experimenter), and whether they would subsequently choose to interact with the former when given the choice. In addition, we tested whether ravens that observed the initial seeding of information about who was ‘fair’ or ‘unfair’ could transform bystander information into first-person interactions, i.e. also preferring to interact with the ‘fair’ experimenter when given the choice. The results show that ravens with first-hand experience were more likely to interact with experimenters with whom they had had a positive previous experience, and that this memory lasted at least 1 month. In contrast, observers did not distinguish between the experimenters when given the choice to interact with them. Previous first-hand experience with the paradigm, however, seemed to help observers to be more successful in solving the task, albeit not significantly above chance. In sum, this study shows memory for direct reciprocity in ravens, and tentatively suggests memory for indirect reciprocity. Accordingly, these results provide hints for the underlying mechanism of memory in raven social interactions.FSW – Publicaties zonder aanstelling Universiteit Leide

A comparative approach to affect and cooperation

A central premise of the science of comparative affect is that we can best learn about the causes and consequences of affect by comparing affective phenomena across a variety of species, including humans. We take as a given that affect is widely shared across animals, but a key challenge is to accurately represent each species' affective experience. A common approach in the comparative study of behavior and cognition is to develop standardized experimental paradigms that can be used across species, with the assumption that if the same task is being used, we can directly compare behavioral responses. This experimental approach rests on two underlying assumptions: first, that different species' perception of and affective response to these paradigms are the same; and second, that behavioral and physiological (including endocrine and neural) responses to these paradigms are homologous; if either of these assumptions is not true, then the comparison becomes much less straightforward. Our goal in the present paper is to summarize the dominant paradigms that have been used for such comparative research, with a particular focus on paradigms common in the cooperation literature, and to critically discuss dominant assumptions about what affective states these tasks can or should measure. We then consider the advantages and drawbacks of this experimental method, and consider alternatives that may improve our understanding. We hope that this will help scholars recognize and avoid pitfalls inherent in studying affect, and stimulate them to create novel, ecologically relevant paradigms for examining affect across the animal kingdom.Action Contro

Social status and prenatal testosterone exposure assessed via second-to-fourth digit ratio affect 6-9-year-old children's prosocial choices

Prosocial behaviour (i.e., voluntary behaviour intended to benefit another) seems to be fully developed in children by the age of 6 years. However, questions about which factors modify prosocial behaviour at that age remain understudied. Here we used a resource allocation paradigm to test prosocial behaviour in 6–9-year-old school children. They could decide between a “selfish” (i.e., one sticker for themselves) and a “prosocial” option (i.e., one sticker for themselves and one for the receiver) and we tested whether friendship, social status and prenatal androgen exposure (approximated by the 2nd to 4th digit ratio; 2D:4D) influenced children’s prosocial choices. We found that children behaved prosocially, and that their prosocial tendencies were negatively correlated with prenatal androgen exposure; i.e., children with high 2D:4D ratios (reflecting low prenatal androgen exposure) acted more prosocially than children with low 2D:4D ratios. Further, their social status in the classroom influenced their choices: children with fewer interaction partners chose the “prosocial” option more often than more ‘popular’ children. However, they did so irrespectively of whether they were paired with a recipient or not. Our results highlight the importance of considering social, as well as physiological factors when investigating prosocial behaviour in children.FSW – Publicaties zonder aanstelling Universiteit Leide

Behavioural and hormonal stress responses to social separation in ravens, Corvus corax

FSW – Publicaties zonder aanstelling Universiteit Leide

'Friendship' in Macaques : economics and emotions

Both in humans and group-living animals, individuals affiliate more with some individuals than others. Human friendships have long been acknowledged, and recently scientists studying animal behaviour have started using the term friendship for social bonds between animals. Yet, while biologists describe friends as social tools to enhance fitness, social scientists argue that human friendships are unconditional. Therefore, I investigate whether these different descriptions reflect true differences in human and animal friendships or whether they are a by-product of different research approaches: namely social scientist focussing on proximate and biologists on ultimate explanations. In this thesis I studied friendships of long-tailed and rhesus macaques. I defined as friends those dyads with individuals that were in close contact and groomed each other relatively more frequently than others. First, I studied exchange relations of both species. I show that macaques of both species exchange grooming and support. Moreover, I show that male rhesus macaques exchange grooming for sexual access to females. However, these exchanges are not based on immediate reciprocity, but are better explained by the long-term emotional bond between dyads. Since these macaques exchange services on an unconditional base, it is expected that they also show pro-social behaviour and that its frequency depends on the strength of such a bond, e.g., friends give more to each other than non-friends. In an experimental set-up, I tested pro-sociality in long-tailed macaques and how that is affected by relationship quality. Surprisingly, pro-social behaviour is not used by subordinates to obtain benefits from dominants, but by dominants to emphasize their dominance position, while subordinates withhold their partners access to food, and seem to prefer a more competitive strategy. When given the choice to give to either a ‘friend’ or a ‘non-friend’, only dominant individuals give to their friends, while subordinates prefer a more competitive strategy and give to the most dominant individual. Therefore, dominance rank determines which of two possible social relationships, friendship or dominance, prevails in directing pro-social behaviour. Only dominants seem to confirm their ‘friendships’ in the short-term setting of an experiment. Another assumption of friendship concerns tolerance for an imbalance within what is given and received. Yet, when tested experimentally, long-tailed macaques do show an aversion to a cost-benefit imbalance, regardless of whether they are paired with a ‘friend’ or a ‘non-friend’. Finally, I review studies on both human and animal friendships. I show that both human and animal friendships are adaptive. Yet, these friendships are not motivated by these fitness benefits, but are unconditional. Moreover, friendships are probably mediated by emotions and such a regulation of social bonds is a highly conserved system of sociality in humans and is similar in many animals. In conclusion, when biologists and social scientist describe close bond among monkeys and humans, they describe the same homologue phenomenon, and the use of the term friendship for animals, therefore, seems justified

Why contagious yawning does not (yet) equate to empathy

Various studies and researchers have proposed a link between contagious yawning and empathy, yet the conceptual basis for the proposed connection is not clear and deserves critical evaluation. Therefore, we systematically examined the available empirical evidence addressing this association; i.e., a critical review of studies on inter-individual differences in contagion and self-reported values of empathy, differences in contagion based on familiarity or sex, and differences in contagion among individuals with psychological disorders, as well as developmental research, and brain imaging and neurophysiological studies. In doing so, we reveal a pattern of inconsistent and inconclusive evidence regarding the connection between contagious yawning and empathy. Furthermore, we identify study limitations and confounding variables, such as visual attention and social inhibition. Future research examining links between contagious yawning and empathy requires more rigorous investigation involving objective measurements to explicitly test for this connection.</p

Sneaky Monkeys: An Audience Effect of Male Rhesus Macaques (Macaca mulatta) on Sexual Behavior

Males and females have different sexual interests and subsequently may show conflicting sexual strategies. While dominant males try to monopolize females, promiscuity benefits females and subordinate males. One way to escape monopolization by dominant males is to copulate in their absence. We tested this inhibitory effect of males on the sexual behavior of their group members in captive group-living Rhesus macaques. Copulations between females and nonalpha males almost exclusively took place when the alpha male was out of sight. Furthermore, the inhibiting effect was not unique for the alpha male. An upcoming nonalpha male also inhibited copulations of its group members, and three other nonalpha males inhibited female copulation solicitations. Females adjusted their behavior to the presence of bystander males, as they initiated and accepted initiations more often in absence than in presence of bystander males. Although not significant, in males, a similar pattern was found. The observed reduction in mating behavior in presence of bystander males is in accordance with an "audience effect," in which the behavior is modulated in relation to the presence or absence of third parties. This audience effect may serve as an important mechanism to reduce (aggressive) interruptions of subordinate male copulations. © 2012 Wiley Periodicals, Inc

Sneaky Monkeys: An Audience Effect of Male Rhesus Macaques (Macaca mulatta) on Sexual Behavior

Males and females have different sexual interests and subsequently may show conflicting sexual strategies. While dominant males try to monopolize females, promiscuity benefits females and subordinate males. One way to escape monopolization by dominant males is to copulate in their absence. We tested this inhibitory effect of males on the sexual behavior of their group members in captive group-living Rhesus macaques. Copulations between females and nonalpha males almost exclusively took place when the alpha male was out of sight. Furthermore, the inhibiting effect was not unique for the alpha male. An upcoming nonalpha male also inhibited copulations of its group members, and three other nonalpha males inhibited female copulation solicitations. Females adjusted their behavior to the presence of bystander males, as they initiated and accepted initiations more often in absence than in presence of bystander males. Although not significant, in males, a similar pattern was found. The observed reduction in mating behavior in presence of bystander males is in accordance with an "audience effect," in which the behavior is modulated in relation to the presence or absence of third parties. This audience effect may serve as an important mechanism to reduce (aggressive) interruptions of subordinate male copulations. © 2012 Wiley Periodicals, Inc

A comparative approach to affect and cooperation

A central premise of the science of comparative affect is that we can best learn about the causes and consequences of affect by comparing affective phenomena across a variety of species, including humans. We take as a given that affect is widely shared across animals, but a key challenge is to accurately represent each species' affective experience. A common approach in the comparative study of behavior and cognition is to develop standardized experimental paradigms that can be used across species, with the assumption that if the same task is being used, we can directly compare behavioral responses. This experimental approach rests on two underlying assumptions: first, that different species' perception of and affective response to these paradigms are the same; and second, that behavioral and physiological (including endocrine and neural) responses to these paradigms are homologous; if either of these assumptions is not true, then the comparison becomes much less straightforward. Our goal in the present paper is to summarize the dominant paradigms that have been used for such comparative research, with a particular focus on paradigms common in the cooperation literature, and to critically discuss dominant assumptions about what affective states these tasks can or should measure. We then consider the advantages and drawbacks of this experimental method, and consider alternatives that may improve our understanding. We hope that this will help scholars recognize and avoid pitfalls inherent in studying affect, and stimulate them to create novel, ecologically relevant paradigms for examining affect across the animal kingdom