Behavioral task to assess physical causal understanding in rats (Rattus norvegicus)

Abstract

Several studies have attempted to reveal the evolutionary mechanisms of physical causal understanding in non-human animals by investigating their tool-use behavior. Rats are one of the most commonly used species in experiments in many fields, including neuroscience and physiological psychology, but behavioral tasks for investigating the mechanisms in rodents have not yet been established. The present study implemented a novel training paradigm: a rake-shaped tool was presented in the experimental apparatus without a reward. If rats manipulated the rake laterally over specific distances, the experimenter retrieved the rake and offered the reward by hand. The rats never obtained food directly with the tool during training, and the tool never touched the reward. In the test, the rake was placed at the center of the apparatus, and the reward was placed on either the left or right side of the rake. The rats had no prior experience of obtaining the reward with the tool before the test, and they could not use this simple strategy to manipulate the rake in the direction of the reward during the test. One of eight rats could manipulate the rake according to the position of the reward. The present study offers a tool-use task to reveal the evolutionary mechanisms of physical causal understanding.