Species and Sex Differences in Response to a Novel Stimulus in Acomys Cahirinus and Mus Musculus

Abstract

An experiment is described in which the relative distractibility of two species of murid rodent, Acomys cahvrinus and Mus musculus, was compared. On the basis of observations derived from our previous studies of exploratory behaviour in males of these two species, we predicted that Mus would show higher levels of distractibility when presented an unexpected, novel stimulus than would Acomys. Distractibility was measured using a novel stimulus placed on the wall of a runway along which the animals had been trained to run to a food reward. The hypothesis was not supported, at least for males; indeed, male Acomys were more easily distracted from the runway task by introduction of the novel stimulus than male Mus. Among females, however, the species difference was reversed for female Mus were highly responsive to the novel stimulus. The most significant difference shown in this experiment appears, however, to be that between male and female Mus, since male Mus showed relatively little response to the stimulus change. The results are discussed in relation to possible hormone differences and differences between the species, in responses to novelty.