Rats' (Rattus norvegicus) tool manipulation ability exceeds simple patterned behavior.

Akane Nagano

doi:10.1371/journal.pone.0226569

Abstract

Many studies have attempted to shed light on the ability of non-human animals to understand physical causality by investigating their tool-use behavior. This study aimed to develop a tool-manipulation task for rodents in which the subjects could not manipulate the tool in the direction of the reward by simple patterned behavior. Eight rats had to use a rake-shaped tool to obtain a food reward placed beyond their reach. During the training, the rats never moved the rakes laterally to obtain the reward. However, in the positional discrimination test, the rake was placed at the center of the experimental apparatus, and the reward was positioned on either the left or right side of the rake. Interestingly, this test indicated that some rats were able to manipulate the rake toward the reward without relying on a patterned behavior acquired during the training. These results suggested that rats have the primitive ability to understand causal relationships in the physical environment. The findings indicate that rats can potentially serve as an animal model to investigate the mechanisms of evolution and development of the understanding of physical causality in humans.

Highlights

Some studies have suggested that non-human animals can understand causal relationships among multiple objects in the physical world [1, 2], suggesting that they can comprehend how the antecedent event A produces the consequent event B, and not just understand the order of the two events; i.e., that event B always occurs after event A [2]
Further research using a wider variety of species in controlled experimental settings is needed to elucidate the mechanisms of evolution and development of the understanding of physical causality in humans
The analysis of the positional discrimination test determined whether the rats manipulated the rake without guides toward the reward or not, and compared the number of trials in which the rake was moved in either direction (40 trials)

Summary

Introduction

Some studies have suggested that non-human animals can understand causal relationships among multiple objects in the physical world [1, 2], suggesting that they can comprehend how the antecedent event A (the cause) produces the consequent event B (the effect), and not just understand the order of the two events; i.e., that event B always occurs after event A [2]. In studies on rodents, including rats (Rattus norvegicus) [3, 4] and degus (Octodon degus) [5, 6], few have investigated the physical causal understanding in controlled experimental settings. In these previous studies, the subjects were commonly required to use a tool to obtain a reward beyond their reach. The subjects were commonly required to use a tool to obtain a reward beyond their reach These studies suggested that rodents can understand the spatial

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