Secondary representational abilities in nonhuman primates (Macaca nemestrina, Cebus apella)

Abstract

As human infants mature, their cognitive operations achieve increasing levels of complexity, which is thought to be based on an increasing complexity of their mental representational abilities. Perner (1991) proposed three different types of mental representations that are believed to underlie this development: primary representations, which represent reality accurately and faithfully; secondary representations, which are ‘detached’ from immediate reality and therefore capable of modelling past or future situations; and metarepresentations, which explicitly represent the relationship between the representation and its content. Numerous studies have provided evidence that in humans, primary representations appear to be present from birth, secondary representations emerge between 1.5-2 years, and metarepresentations develop between 4.5-5 years. Much less is known with regard to the phylogenetic development of representational abilities. Studies with nonhuman primates suggest the presence of primary and secondary representational abilities in great apes, but only primary representational abilities in monkeys. However, the current lack of evidence for secondary representational abilities in monkeys might be related to the limited number of studies addressing this issue and/or methodological limitations, thereby perhaps not reflecting a true negative. In order to contribute towards a more complete picture of nonhuman primates’ representational abilities, a series of studies was conducted to examine secondary representational abilities in two monkey species (Macaca nemestrina, Cebus apella). Pig-tailed macaques were tested for self-imitation, imitation recognition and mirror self-recognition; capuchin monkeys were tested for imitation recognition, mirror self-recognition and means-ends reasoning, all thought to be indicative of secondary representational abilities. Evidence for primary representations was found in both species, however none of the experiments provided strong evidence for secondary representational abilities. One possible exception is two pig-tailed macaques’ responses to marks on their heads during a classic mark test for self-recognition, but since these responses consisted of mere swipes to their heads and not intensive mirror-mediated responding, this finding cannot be regarded as conclusive. The absence of evidence for secondary representational abilities in monkeys in the present work therefore confirms previous research findings and may suggest that monkeys are limited to primary representational abilities. Replications and extensions of the present work are highly recommended and can significantly contribute to our understanding of the evolutionary origin of human and nonhuman primate cognition.