Relational complexity influences analogical reasoning ability

Human language without analogy is like a zebra without stripes. The ability to understand analogies, or to engage in relational reasoning, has been argued to be an important distinction between the cognitive abilities of human and non-human animals. Current studies have failed to robustly show that animals can perform more complex, relational discriminations, in part because such tests rely on linguistic or symbolic experiences, and therefore are not suitable for evaluating analogical reasoning in animals. We report on a methodological approach allowing for direct comparisons of analogical reasoning ability across species. We show that human participants spontaneously make analogical discriminations with minimal verbal instructions, and that the ability to reason analogically is affected by analogical complexity. Furthermore, performance on our task correlated with participants' fluid intelligence scores. These results show the nuance of analogical reasoning abilities by humans, and provide a means of robustly comparing this capacity across species.