Proximity to Rewards Modulates Parameters of Effortful Control Exertion

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, goal gradient-like behaviour 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 towards 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.