Performance-linked rewards shape cognitive effort in 30-person study

In a peer-reviewed study of 30 people, rewards linked to correct task performance produced clear changes in response time, accuracy and phasic pupil size, while reward level and time on task showed no clear effects on those measures. The experiment examined whether efficacy—the perceived relationship between successful performance and reward—continued to influence cognitive effort allocation across relatively long task blocks. The researchers used a block-design Stroop task and manipulated two experimental factors.

Possible rewards were either contingent upon correct performance or determined without regard to performance, establishing different levels of efficacy. Separate blocks provided high or low reward levels. Each block was divided into two halves, allowing the researchers to assess time-on-task effects.

They recorded response time, accuracy, tonic and phasic pupil size, and blink rate and duration. A mixed-effects modelling approach was used to evaluate the effects of efficacy, reward, time on task and their interactions. This design tested the proposed cost-benefit account of cognitive effort, under which effort allocation reflects subjective costs and possible rewards, with efficacy moderating how those elements are integrated.

Behavioral results provided the strongest evidence for an efficacy effect: response time and accuracy showed clear differences according to whether reward was contingent on successful performance. A broadly similar pattern appeared in phasic pupil size. Neither time on task nor reward level had a clear impact on these behavioral or phasic pupil measures.

The results therefore support efficacy, rather than reward magnitude alone, as a factor associated with effort allocation during the task. Instead, the clear distinction concerned whether possible rewards were determined by correct performance. Measures of tonic pupil size and blinking produced a more complex pattern.

These measures suggested time-on-task effects, and reward or efficacy attenuated those effects in some analyses. Their relationship to the behavioral results was not straightforward, however, and some interaction patterns were theoretically ambiguous. Because these ocular findings diverged from the response-time and accuracy outcomes, the researchers advised cautious interpretation and emphasized the interpretive complexity of using ocular measures to study cognitive effort over time.

The sample of 30 participants and the scope of the block-design experiment limit generalization, while the absence of clear time-on-task effects in the main behavioral measures means the study should not be read as evidence of a general decline in effort as people continued working. Overall, the findings support a sustained role for efficacy in effort-related cost-benefit calculations and show that different indicators of cognitive effort need not change in parallel.

Subject of Research: How performance-contingent rewards influence cognitive effort allocation over task blocks

Article Title: Been around the block: The sustained influence of efficacy on cognitive effort allocation over time

Article References: Louter, W. J., Steendam, S. T., Prutean, N., Eayrs, J. O., Kukkonen, N., Notebaert, W., Krebs, R. M., Wiersema, J. R., & Boehler, C. N. (2026). Been around the block: The sustained influence of efficacy on cognitive effort allocation over time. BMC Psychology. https://doi.org/10.1186/s40359-026-05453-x

Image Credits: AI Generated

DOI: 10.1186/s40359-026-05453-x

Keywords: cognitive effort, reward contingency, efficacy, Stroop task, pupil size, eye blinking, response time, time on task, mixed-effects models, Been, around, block