Abstract
Impulsivity and stress exposure are two factors that are associated with changes in reward-related behavior in ways that are relevant to both healthy and maladaptive decision-making. Nonetheless, little empirical work has examined the possible independent and joint effects of these factors upon reward learning. Here, we sought to examine how trait impulsivity and acute stress exposure affect participants’ choice behavior and decision speed in a two-stage sequential reinforcement-learning task. We found that more impulsive participants were more likely to repeat second-stage choices after previous reward, irrespective of stress condition. Exposure to stress, on the other hand, was associated with an increased tendency to repeat second-stage choices independent of whether these choices previously led to a reward, and this tendency was exacerbated in more impulsive individuals. Such interaction effects between stress and impulsivity were also found on decision speed. Stress and impulsivity levels interacted to drive faster choices overall (again irrespective of reward) at both task stages, while reward received on the previous trial slowed subsequent first-stage choices, particularly among impulsive individuals under stress. Collectively, our results reveal novel, largely interactive effects of trait impulsivity and stress exposure and suggest that stress may reveal individual differences in decision-making tied to impulsivity that are not readily apparent in the absence of stress.
Highlights
Impulsivity and stress exposure are two factors that are associated with changes in reward-related behavior in ways that are relevant to both healthy and maladaptive decision-making
Based on prior findings using simple reinforcement learning (RL) tasks, we hypothesized that impulsivity and acute stress might exert independent or joint effects on learning as indicative of enhanced reward responsivity
Our analysis focused on possible relationships between acute stress and individual differences in impulsivity, and their interaction, on first- and second-stage choice behavior as a function of previous rewards—in effect, focusing on ‘model-free’ features of choice—and choice response times (RTs) as a function of previous rewards and state transitions
Summary
Impulsivity and stress exposure are two factors that are associated with changes in reward-related behavior in ways that are relevant to both healthy and maladaptive decision-making. Both acutely stressed participants and participants high in trait impulsivity exhibit increased response repetition after positive reinforcement, and faster response times (RTs) in simple RL tasks[16,45,46,47] These effects on learning and decision-making are thought to occur either by stress ‘occupying’ or impairing cognitive resources that allow for more deliberative decision-making processes[55,56] or by both factors imposing internally perceived time constraints that manifest in differential choice speeding[25,57,58]. It remains unclear whether stress and impulsivity and independently influence features of reward learning, or whether they interact such that stress acts jointly with trait impulsivity to alter choice behavior
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