Exploring the Winner-Loser Effect on Emotion in Crickets

Abstract

Individual variation in behavioral traits, commonly referred to as personality, is exhibited in numerous animal species, including invertebrates. The specific personality trait of exploration tendency may be affected by positive/optimistic or negative/pessimistic emotional states. Animal contests can induce these emotions, as winning against ones opponent increases optimism, while losing causes pessimism; these states can then affect behavior in other contexts. Previous studies demonstrate that house crickets (Acheta domesticus) experience this winner-loser effect in fights, thus we investigated if a crickets exploratory behavior is influenced by the outcome of its contest. We predicted that after a fight, winners would exhibit increased exploratory behavior due to an optimistic emotional state, while losers would show decreased exploratory behavior due to a pessimistic emotional state. Exploration tendency was measured as an individuals latency to exit a shelter. Crickets then participated in an aggression contest, with opponents chosen to be smaller or larger so that focal individuals either won (n=33) or lost (n=31), respectively. Latency to exit was again measured after the contest, as well as 48 h later to examine the persistence of winner-loser effects on exploration behavior over extended time periods. Latencies for control crickets (n=40) were measured at the same time points, but controls did not engage in a fight. In one of two years, winning crickets latency times decreased following the contest, while losing crickets latency times were not significantly affected. This suggests that individuals emotional states were changed by the experience of winning a fight, which affected exploration tendencies, while losing a fight does not have an effect on exploration tendency. These data on invertebrate emotions have important implications for human health by allowing for future studies on the mechanisms behind mental states.