Proximity to rewards modulates parameters of effortful control exertion.

Abstract

The now-classic goal-gradient hypothesis posits that organisms increase effort expenditure as a function of their proximity to a goal. Despite nearly a century having passed since its original formulation, goalgradient-like behavior in human cognitive performance remains poorly understood: Are we more willing to engage in costly cognitive processing when we are near, versus far, from a goal state? Moreover, the computational mechanisms underpinning these potential goal-gradient effects-for example, whether goal proximity affects fidelity of stimulus encoding, response caution, or other identifiable mechanisms governing speed and accuracy-are unclear. Here, in two experiments, we examine the effect of goal proximity, operationalized as progress toward the completion of a rewarded task block, upon task performance in an attentionally demanding oddball task. Supporting the goal-gradient hypothesis, we found that participants responded more quickly, but not less accurately, when rewards were proximal than when they were distal. Critically, this effect was only observed when participants were given information about goal proximity. Using hierarchical drift diffusion modeling, we found that these apparent goal-gradient performance effects were best explained by a collapsing bound model, in which proximity to a goal reduced response caution and increased information processing. Taken together, these results suggest that goal gradients could help explain the oft-observed fluctuations in engagement of cognitively effortful processing, extending the scope of the goal-gradient hypothesis to the domain of cognitive tasks. Public Significance StatementIt is well known that humans and animals alike tend to work harder as they near a goal. Whether it be a hungry rat moving closer to a food reward or a runner sprinting the final kilometer of a race, organisms appear to intensify their effort as a function of their proximity to a goal. But does the same principle apply in purely mental tasks-for example, when writing an exam, or doing one's taxes? And if so, how does behavior change? In these studies, we examine whether proximity to a goal affects a person's willingness to exert mental effort in a simple, but cognitively demanding task. Consistent with the established goal-gradient hypothesis, we find that participants intensified their level of cognitive effort-as indexed by their response speed and ability to correctly respond-closer to a goal (vs. further away). Using computational modeling, we found that while participants processed information more efficiently near a goal, they were also less cautious in their decision making. Taken together, our results extend past findings about the effects of goal proximity on effort to the domain of purely cognitive tasks.