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Something’s Gotta Give: Reward-Induced Effort Modulations in Task Switching Reveals a Trade-Off Between Cognitive Flexibility and Stability

Poster Session E - Monday, March 9, 2026, 2:30 – 4:30 pm PDT, Fairview/Kitsilano Ballroom

Nathan K. Mathews¹ (), Senne Braem², Eliana Vassena^3,4, A. Ross Otto¹; ¹McGill University, ²Ghent University, ³Radboud University Nijmegen, ⁴Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen

Everyday behaviour requires balancing two control modes: cognitive stability, for maintaining task goals in the face of distraction, and cognitive flexibility, for switching efficiently between task sets. According to one influential proposal, these opposing modes effectively trade off with one another: increased flexibility comes at the cost of reduced stability, and vice-versa. However, empirical support for a tradeoff has been equivocal. Here, we examine whether a flexibility-stability trade-off emerges under reward-induced effort modulation, that is, when higher anticipated reward increases mental effort, potentially necessitating prioritization of one control mode over the other. Across two experiments (N = 62 and N = 61), participants completed a task-switching paradigm with cued reward magnitude (1 vs. 10 cents) and block duration (short vs. long). The task was designed to simultaneously measure both control modes. We tracked flexibility and stability using two validated behavioural indices: switch costs, the reaction time (RT) increase on switch vs. repeat trials, and incongruence costs, the RT difference between incongruent and congruent trials. We observed that higher reward incentives increased flexibility (reduced switch costs) but decreased stability (increased incongruence costs), suggesting a reward-induced trade-off. In Experiment 1, this trade-off further unfolded across within-subject, moment-to-moment adjustments in control across blocks, and between-subject differences in individuals’ general tendency toward stability. These findings provide evidence for a reward-driven trade-off, where higher incentives promote flexibility at the cost of stability. We provide rare empirical support that intensifying control engagement through reward may necessitate selective prioritization, yielding a trade-off between cognitive flexibility and stability.

Topic Area: EXECUTIVE PROCESSES: Goal maintenance & switching