抄録
In studies of comparative cognitive science, different species of animals are compared in order to figure out similarities and differences of cognitive abilities based on two possible assumptions. The phylogenetic assumption presumes that the closer the phylogenetic distance of the two species is, the higher the cognitive similarities should be. The ecological assumption, on the other hand, presumes that different species of animals exposed to similar selective pressures should obtain similar cognitive abilities. Based on these assumptions, I compared two group-living species (capuchin monkeys and rats) with two solitary species (tree shrews and hamsters) in an inference task in a social context. Animals were tested whether they infer a consequence of the other individual's behavior that should lead to different values left in two familiar restricted food sites. Results showed that only capuchin monkeys solved the task, suggesting that only primates may have this inference ability. The present species comparison simply treated ecological factors as categorical variables, for example whether animals are social or solitary. I propose a novel approach to species comparison, in which quantitative aspects of various ecological factors are also considered as variables contributing potential species differences.
