Understanding of and reasoning about object–object relationships in long-tailed macaques?

[Correction Notice: An Erratum for this article was reported in Vol 17(1) of Animal Cognition (see record [rid]2014-00148-002[/rid]). In the original article, there are some errors the corrections are present in the erratum.] Diagnostic reasoning, defined as the ability to infer unobserved causes based on the observation of their effects, is a central cognitive competency of humans. Yet, little is known about diagnostic reasoning in non-human primates, and what we know is largely restricted to the Great Apes. To track the evolutionary history of these skills within primates, we investigated long-tailed macaquesʼ understanding of the significance of inclinations of covers of hidden food as diagnostic indicators for the presence of an object located underneath. Subjects were confronted with choices between different objects that might cover food items. Based on their physical characteristics, the shape and orientation of the covers did or did not reveal the location of a hidden reward. For instance, hiding the reward under a solid board led to its inclination, whereas a hollow cup remained unaltered. Thus, the type of cover and the occurrence or absence of a change in their appearance could potentially be used to reason diagnostically about the location of the reward. In several experiments, the macaques were confronted with a varying number of covers and their performance was dependent on the level of complexity and on the type of change of the coversʼ orientation. The macaques could use a boardʼs inclination to detect the reward, but failed to do so if the lack of inclination was indicative of an alternative hiding place. We suggest that the monkeysʼ performance is based on a rudimentary understanding of causality, but find no good evidence for sophisticated diagnostic reasoning in this particular domain. (PsycINFO Database Record (c) 2016 APA, all rights reserved)

Sponsor: Leibniz Graduate School. Other Details: Foundations of Primate Social Behaviour. Recipients: No recipient indicated