Animals make beneficial decisions for survival by evaluating positive or negative experiences induced by environmental stimuli. Aversive experiences play an important role in helping animals avoid dangerous environments and reduce harm. For instance, the aversive valence led the animals to concede defeat during fights, minimizing harm to individuals and increasing their chances for survival. The ventral habenula-raphe circuit has been demonstrated to be involved in the evaluation of aversive valence in active avoidance test. Both the neural activity in the ventral habenula (vHb) and raphe increased after repeated social defeats and silencing the vHb-raphe circuit impaired the learning efficiency of active avoidance test. These indicate that the activity in the raphe evaluates aversive valence and also control dyadic social aggressive behaviors. We therefore hypothesized that activation of the raphe nucleus after social conflict affects adaptive learning. We expected that after social defeat, the neural plasticity in the raphe changes, which increases learning ability or efficiency in loser fish during adaptive learning task. In our experiment design, we first performed dyadic fighting test to identify winner and loser fish and then applied both winner and loser fish to an active avoidance test. Our result would provide clues to elucidate the functions of raphe for animals to acclimate the environmental dangers