Same/Different Concept Learning by Capuchin Monkeys in Matching-to-Sample Tasks

Valentina Truppa,Duilio Garofoli,Elisabetta Visalberghi,Sara Privitera,Eva Piano Mortari,Laurie Santos

doi:10.1371/journal.pone.0023809

Abstract

The ability to understand similarities and analogies is a fundamental aspect of human advanced cognition. Although subject of considerable research in comparative cognition, the extent to which nonhuman species are capable of analogical reasoning is still debated. This study examined the conditions under which tufted capuchin monkeys (Cebus apella) acquire a same/different concept in a matching-to-sample task on the basis of relational similarity among multi-item stimuli. We evaluated (i) the ability of five capuchin monkeys to learn the same/different concept on the basis of the number of items composing the stimuli and (ii) the ability to match novel stimuli after training with both several small stimulus sets and a large stimulus set. We found the first evidence of same/different relational matching-to-sample abilities in a New World monkey and demonstrated that the ability to match novel stimuli is within the capacity of this species. Therefore, analogical reasoning can emerge in monkeys under specific training conditions.

Highlights

The use of abstract concepts improves the ability to sort objects, events, and relations into common classes on the basis of shared perceptual, associative, and relational properties and to transfer knowledge to new stimuli or contexts
The current study evaluates the ability of the New World tufted capuchin monkeys (Cebus apella) to learn same and different abstract concepts and to use them to solve a relational matching task that mirrored the tasks presented to apes [13,19], Old World monkeys
The aims of our study were to assess: (1) if capuchin monkeys previously trained to solve MTS tasks on the basis of perceptual similarity (i.e., identity MTS (IDMTS): [18]), are able to use same/ different concept to solve MTS tasks on the basis of relational similarity (i.e., relational MTS (RMTS)); (2) whether or not performance can be improved by increasing the number of training stimuli and/or by increasing the number of items composing the stimuli

Summary

Introduction

The use of abstract concepts improves the ability to sort objects, events, and relations into common classes on the basis of shared perceptual, associative, and relational properties and to transfer knowledge to new stimuli or contexts. In humans, these capabilities underpin advanced cognitive skills such as analogical reasoning. Abstract concept learning has been mostly investigated by using same/different discrimination tasks, in which subjects had to judge whether two items are physically the same or different [7] These tasks require subjects to judge attributes shared in common between stimuli to be compared, i.e. first-order relations. It requires subjects to understand whether the relationship among attributes of objects belonging to one set is equivalent to the relationship among objects belonging to another set (e.g., sets of objects of the same shape), with objects belonging to different sets always having different shapes

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