|dc.description.abstracteng||An advantage of being a group-living-, as opposed to a solitary-species, is having the opportunity to engage with conspecifics in mutually beneficial cooperative activities. Choice of cooperation partner often decides whether a cooperative venture succeeds or fails. Cooperation therefore, calls for the careful evaluation of conspecifics. The ideal partner treats others well (shows commitment and values fairness) and has the requisite competence to be able to contribute to the task at hand. This dissertation, comprised of two studies (three experiments), aimed to further what we know about the social evaluation skills of humans and non-human primates. Specifically, I investigated how individuals evaluate others with respect to fairness and competence.
In Study 1, I investigated whether a catarrhine species - the long-tailed macaque (Macaca fascicularis) - is sensitive to fairness. Experiments have shown that non-human primates refuse food if they are poorly paid for work compared to a conspecific. I investigated whether refusal behaviour is due to social comparison with the well-paid conspecific, or disappointment in the distributor who rewards poorly. I manipulated two factors: (1) partner presence and (2) type of distributor; half of the subjects experienced a human distributor, the other half a machine distributor. In inequality test conditions, subjects received low-value food while the partner (when present) received high-value food. In an equality control condition, subject and partner received the same low-value food. I measured food refusal behaviour. Study 1 revealed (1) an effect of distributor under conditions of inequality; monkeys who were rewarded by the human, refused food more often compared to those rewarded by the machine (2) no effect of distributor under conditions of equality; irrespective of distributor type, food refusal rates were low when both animals received the same value food and (3) monkeys worked faster when the partner was present, compared to when they were alone.
In Study 2, I investigated how four- to seven-year-old children evaluate and apply competence information in different co-action settings. I designed two online experiments to investigate whether the inference processes thought to be at play in cooperative contexts (trait-reasoning and simple heuristics), are evident in the competitive context - a second setting that calls for a similar strategic use of competence information. In Experiment 1, participants learned about the strength of two models - one model was strong, the other weak. In test trials, participants had to recruit a co-action partner for competitive and cooperative strength games and a co-action partner for either a competitive or a cooperative knowledge game. Experiment 1 revealed that the older children recruited rationally in both contexts for the strength games, and that children of all ages generalized in both contexts, transferring strength competence information to the knowledge domain. In Experiment 2, participants learned about the strength and object-labelling competence of two models (one model was physically strong but inaccurate at object-labelling, while the other model was physically weak but accurate at object-labelling). In test trials, participants had to recruit a co-action partner for competitive and cooperative strength and knowledge games. Experiment 2 was inconclusive. The children showed little rational recruitment behaviour in either co-action context.
It is possible to draw two conclusions from these studies. Study 1 shows that multiple factors mediate subjects’ food refusal behaviour in an impunity experiment; social disappointment in the human distributor, social comparison with the conspecific and food competition all had an effect on refusal behaviour in this experiment. A study limitation (the test conditions were run before the control conditions) however, means that it would be premature to conclude that the social comparison effect we observe, is evidence that long-tailed macaques perceive inequality (are sensitive to fairness). It is possible that by the end of the experiment, subjects were simply tired of refusing food. Future work that counterbalances condition presentation order, could clarify whether we are looking at a three-factor explanation in this species, or whether a two-factor explanation would suffice. From Study 2, I tentatively conclude that the inferential processes (trait-reasoning and a simple decision heuristic) thought to explain children’s partner recruitment decisions in cooperative contexts, are also present in the competitive context. Experiment 2 would have been necessary to confirm that trait-reasoning was behind the rational recruitment choices in Experiment 1. These two child experiments were run online. It would be valuable to obtain in-presence data to establish whether demands of the online setting masked children’s trait-reasoning abilities in Experiment 2.||de