Starlings solve the ephemeral reward task.

Abstract

In the ephemeral reward task, animals are presented with two choice alternatives, one optimal, the other suboptimal. Choosing the suboptimal alternative delivers one immediate reward and ends the trial, whereas choosing the optimal alternative also yields one immediate reward but allows subsequent access to the reward associated with the suboptimal alternative. While species such as cleaner wrasse and grey parrots excel at this task, others-including pigeons, primates, and rats-struggle, raising questions about the factors influencing success. This study investigated these factors by examining performance in starlings under standard and modified task conditions. Across two experiments, starlings successfully learned to prefer the optimal option. In these experiments, we occasionally included single-option trials, which allowed birds to experience the outcomes of each choice in isolation. In Experiment 2, we also manipulated the delay between the two sequential rewards to test its effect on performance. Preference for the optimal option declined as the delay increased, suggesting that shorter delays facilitate credit assignment to the initial choice. We hypothesize that shorter delays facilitate the association between initial choices and subsequent rewards and that differences in apparatus, intertrial intervals, and the rate of memory decay may also influence performance in the task. Overall, our results highlight the complexity of the ephemeral reward task and suggest the potential interplay of ecological relevance and task design. (PsycInfo Database Record (c) 2025 APA, all rights reserved).