The Memory Trace Supporting Lose-Shift Responding Decays Rapidly after Reward Omission and Is Distinct from Other Learning Mechanisms in Rats.

The propensity of animals to shift choices immediately after unexpectedly poor reinforcement outcomes is a pervasive strategy across species and tasks. We report here that the memory supporting such lose-shift responding in rats rapidly decays during the intertrial interval and persists throughout training and testing on a binary choice task, despite being a suboptimal strategy. Lose-shift responding is not positively correlated with the prevalence and temporal dependence of win-stay responding, and it is inconsistent with predictions of reinforcement learning on the task. These data provide further evidence that win-stay and lose-shift are mediated by dissociated neural mechanisms and indicate that lose-shift responding presents a potential confound for the study of choice in the many operant choice tasks with short intertrial intervals. We propose that this immediate lose-shift responding is an intrinsic feature of the brain's choice mechanisms that is engaged as a choice reflex and works in parallel with reinforcement learning and other control mechanisms to guide action selection.