Effort in oculomotor control: Role of instructions and reward on spatiotemporal eye movement dynamics

Effort is an important theoretical construct in several psychological disciplines, yet there is little consensus on how it manifests in behavior. Here, we operationalized effort as performance improvements beyond speed-accuracy tradeoffs and argue that oculomotor kinematics offer a novel conceptual lens on effort regulation. We investigated the efficiency and persistence of mere task instructions to induce transient effort. In a saccadic selection task, participants were instructed to look at targets as quickly and accurately as possible (standard instructions) or to mobilize all resources and respond even faster and more accurately ("to give 110%," effort instructions). We compared results to standard speeded performance (baseline block) and to a potential upper performance limit linking effort instructions to performance-contingent rewards (reward block). Eye movements were faster, more accurate, and initiated earlier when effort was instructed. Yet, these effects were more strongly pronounced and more persistent over time when effort was additionally rewarded. Importantly, a simultaneous improvement in speed and accuracy was only observed with reward. Altogether, the present findings show that instructions may spark effort, but reward sustains it, turning volatile engagement into lasting performance. This underscores that effort thrives when driven by purpose. (PsycInfo Database Record (c) 2025 APA, all rights reserved).