Individual Differences in Behavioural Reaction to a Changing Environment in Mice and Rats

Aggressive and non-aggressive male mice differ in their reaction to a changing social environment. In order to investigate if this differentiation holds also for non-social situations male mice are trained in a standard maze task, whereafter a change (extramaze and intramaze, respectively) is introduced. The results indicate that aggressive males fulfil their task fairly routine-like and do not react to a change which is in contrast to the non-aggressive individuals. In a second experiment a more continuously changing situation is created by testing the animals every 3 trials in a different maze configuration. In this situation in which a routine cannot be developed c.q. used, the aggressive males performed worse than the non-aggressive animals. It is suggested that the behaviour of aggressive males is mainly controlled by intrinsic factors whereas the behaviour of non-aggressive males is more dependent on external factors. Similar results are obtained when repeating the experiments with rats. This indicates that the relation between aggression and behavioural reaction to a changing environment has more general validity. The possibly underlying mechanism is discussed as well as the consequences for the functioning of the animals in a social setting