Both theoretical considerations and methodological constraints explain why the experimental study of animal aggression does not often put much emphasis on individual differences and hardly uses the concept of ‘personality’. And yet, if neurobiologists consider those brain mechanisms that underlie the interpretation of a given situation and the anticipation of a method to cope with it, they are led to investigate mechanisms that underlie a number of behaviour dimensions which the psychologist would refer to as ‘personality’. The actual object considered in either case does not essentially differ. This is exemplified more concretely by examining the kind of factors—and the brain mechanisms involved in their very existence or in their processing—that contribute to determine the probability that in the face of a given situation, a given individual will adopt aggressive behaviour as the coping strategy.