Signaled occurrences of food, rivals, predators, or mates produce Pavlovian-conditioned anticipatory responses in all vertebrates, including humans. The ability of so many different animals to exhibit this type of learning in so many different contexts would suggest that the anticipatory response is probably highly adaptive. However, despite intense interest shown in the biological function of Pavlovian conditioning over the last twenty-five years, direct experimental investigations have been sparse. Recently, however, several studies have demonstrated the adaptive value of Pavlovian conditioning in the aggressive and reproductive behavior of a territorial freshwater fish. The aim of this project is to explore in greater detail the way in which Pavlovian conditioning enhances animals' aggressive and reproductive strategies. One study will determine whether signals accompanying aggressive encounters predispose winners and losers to assume different strategies in subsequent contests. Other experiments will explore how conditioning affects the frequency and duration of aggressive behavior. Finally, the role of signaling in females' choice of mates will be examined. Almost nothing is known about the role that Pavlovian conditioning plays in naturally-occurring aggressive and reproductive behavior, despite the fact that conditioned aggressive and reproductive responses are easily evoked in many animals, including humans. These studies will redress that problem as well as shed light on the long-standing question of what is learned in Pavlovian conditioning.