The Influence of Opponent-Related and Outcome-Related Memory on Repeated Aggressive Encounters in the Paradise Fish (Macropodus opercularis).

The aggressive behavior of male paradise fish (Macropodus opercularis) was studied. Fish were subjected to three aggressive encounters on consecutive days. If submissive males encountered the same opponent three times, the last aggressive encounter was very different than the first one. When the animals faced a new opponent each day, the changes were much less pronounced. We conclude that (1) fish are able to recognize their opponents at least one day after the encounter ("social recognition"), and (2) social recognition modifies the effect of prior defeat ("status-related memory") in subsequent encounters.