Bilateral lesion of the fimbria resulted in a reduction of social interdependency and agonistic behavior in male-male encounters in rats. These findings are hypothesized to be consistent with J. A. Gray's (1982) supervisor model, which assigns an executive function to the septohippocampal system. To achieve this interpretation, social behavior is described in terms of relational processes (social hypothesis, behavioral sequencing, and behavioral competition). This study focused mainly on the effects of the lesion on behavioral sequencing by studying the alterations of the predictability of the behavior of a rat in terms of the behavior of its partner.