Why offense is reduced when rats are tested in a strange cage

Tests of isolation-induced fighting and competitive fighting of rats in various conditions were used to evaluate the hypothesis that there is more offense in a familiar than in a strange cage because of the operation of an “olfactory comparator.” The hypothesis was rejected. Although there was more offense in a familiar than in a strange cage, there was not, as predicted, more offense when Petri dishes containing familiar scent-markings were put in the strange test cage, and there was not, as predicted, a difference in the effect between isolation-induced fighting and competitive fighting. The data were consistent with either one or both of two alternative hypotheses: 1) that the strange cage produces fear (neophobia) that reduces offense; or 2) that the strange cage activates exploratory and scent-marking behaviors that compete with offense. The first of these two alternative hypotheses was also consistent with a finding that handling the test animal prior to a test reduces subsequent offense.