Can old-world and new-world monkeys judge spatial above/below relations to be the same or different? Some of them, but not all of them

Abstract

Chimpanzees (Pan troglodytes) with the aid of token training can achieve analogical reasoning, or the ability to understand relations-between-relations (e.g., Premack, 1976; Thompson, Oden, & Boysen, 1997). However, extraordinarily few numbers of old- and new-world monkeys have demonstrated this ability in variants of relational matching to sample tasks. Moreover, the rarity of replications leaves open the question of whether the results are normative for other captive colonies of the same species. In experiment one we attempted to replicate whether old world rhesus monkeys (Macaca mulatta) might demonstrate the same level of proficiency on a spatial above/below relational matching task as reported for old world baboons (Papio papio). None of the rhesus monkeys attained above chance performances over 10,000 training trials. In experiment two we attempted to replicate results demonstrating that new-world capuchin monkeys (Cebus apella) match above/below relations. The capuchin monkeys performed above chance only in the absence of ‘Clever Hans’ controls for cuing of the correct choice by the experimenters. These failures to replicate previously reported results demonstrate that some, but definitely not all monkeys can judge the equivalence of abstract ‘relations between relations’ and warrant further investigations into the behavioral and cognitive characteristics that underlie these similarities and differences within population and between individuals of different primate species.