The effects of acute stress on the calibration of persistence

Lesions to different regions of frontal cortex have dissociable effects on voluntary persistence

Deciding how long to keep waiting for uncertain future rewards is a complex problem. Previous research has shown that choosing to stop waiting results from an evaluative process that weighs the subjective value of the awaited reward against the opportunity cost of waiting. In functional neuroimaging data, activity in ventromedial prefrontal cortex (vmPFC) tracks the dynamics of this evaluation, while activation in the dorsomedial prefrontal cortex (dmPFC) and anterior insula (AI) ramps up before a decision to quit is made. Here, we provide causal evidence of the necessity of these brain regions for successful performance in a willingness-to-wait task. 28 participants with frontal lobe lesions were tested on their ability to adaptively calibrate how long they waited for monetary rewards. We grouped the participants based on the location of their lesions, which were primarily in ventromedial, dorsomedial, or lateral parts of their prefrontal cortex (vmPFC, dmPFC, and lPFC, respectively), or in the anterior insula. We compared the performance of each subset of lesion participants to behavior in a control group without lesions (n=18). Finally, we fit a newly developed computational model to the data to glean a more mechanistic understanding of how lesions affect the cognitive processes underlying choice. We found that participants with lesions to the vmPFC waited less overall, while participants with lesions to the dmPFC and anterior insula were specifically impaired at calibrating their level of persistence to the environment. These behavioral effects were accounted for by systematic differences in parameter estimates from a computational model of task performance: while the vmPFC group showed reduced initial willingness to wait, lesions to the dmPFC/anterior insula were associated with slower learning from negative feedback. These findings corroborate the notion that failures of persistence can be driven by sophisticated cost-benefit analyses rather than lapses in self-control. They also support the functional specialization of different parts of the prefrontal cortex in service of voluntary persistence.

Statistical information about reward timing is insufficient for promoting optimal persistence decisions

When deciding how long to keep waiting for delayed rewards that will arrive at an uncertain time, different distributions of possible reward times dictate different optimal strategies for maximizing reward. When reward timing distributions are heavy-tailed (e.g., waiting on hold) there is a point at which waiting is no longer advantageous because the opportunity cost of waiting is too high. Alternatively, when reward timing distributions have more predictable timing (e.g., uniform), it is advantageous to wait as long as necessary for the reward. Although people learn to approximate optimal strategies, little is known about how this learning occurs. One possibility is that people learn a general cognitive representation of the probability distribution that governs reward timing and then infer a strategy from that model of the environment. Another possibility is that they learn an action policy in a way that depends more narrowly on direct task experience, such that general knowledge of the reward timing distribution is insufficient for expressing the optimal strategy. Here, in a series of studies in which participants decided how long to persist for delayed rewards before quitting, we provided participants with information about the reward timing distribution in several ways. Whether the information was provided through counterfactual feedback (Study 1), previous exposure (Studies 2a and 2b), or description (Studies 3a and 3b), it did not obviate the need for direct, feedback-driven learning in a decision context. Therefore, learning when to quit waiting for delayed rewards might depend on task-specific experience, not solely on probabilistic reasoning.

Pupillometric evidence for a temporal expectations-based account of persistence under temporal uncertainty

People often quit waiting for delayed rewards when the exact timing of those rewards is uncertain. This behavior often has been attributed to self-control failure. Another possibility is that quitting is the result of a rational decision-making process in the face of uncertainty, based on the decision-maker's expectations about the possible arrival times of the awaited reward. There are forms of temporal expectations (e.g., heavy-tailed) under which the expected time remaining until a reward arrives actually increases as time elapses. In those cases, the rational strategy is to quit waiting when the expected reward is no longer worth the expected time remaining. To arbitrate between the "limited self-control" and "temporal expectations" accounts of persistence, we measured pupil diameter during a persistence task, as a physiological marker of surprise (phasic responses) and effort (pre-decision diameter). Phasic pupil responses were elevated in response to reward receipt. Critically, the extent to which pupils dilated following rewards depended on the delay: people showed larger pupillary surprise responses the more delayed the reward was. This result suggests that people expect the reward less the longer they wait for it-a form of temporal expectations under which limiting persistence is rational. Moreover, predecision pupil diameter before quit events was not associated with how long the participant had been waiting, but rather, depended on how atypical the quit decision was compared with the participant's usual behavior. These data provide physiological evidence for a temporal expectations account of persistence under temporal uncertainty.

Hedonic Consumption in Times of Stress: Reaping the Emotional Benefits Without the Self-Regulatory Cost

Hedonic consumption is pleasant but can interfere with the capacity to self-regulate. In stressful moments, when self-regulation is arguably still important, individuals often indulge in hedonic consumption. In two experiments, we investigate whether hedonic consumption negatively affects self-regulation under moderately stressful conditions and whether selecting hedonic consumption under moderately stressful conditions is driven by high or low self-control. In both studies, participants were randomly exposed to a mental arithmetic task that was either completed under time pressure with performance feedback (moderate stress) or without time pressure and without feedback (no stress). Experiment 1 assigned participants to a hedonic (vs. neutral) consumption task and then measured impulse control via a color-word Stroop task. Experiment 2 measured self-control as a second independent variable and recorded hedonic (vs. neutral) consumption. The results show that moderate stress buffered the negative effect that hedonic consumption has on self-regulation under no stress conditions and that high rather than low self-control predicts hedonic over neutral consumption under stress. These findings indicate that hedonic consumption in response to moderate stress may be a strategic choice to reap the pleasure benefit of hedonic consumption while the costs to self-regulation are low.