Cognitive Exertion Reduces Real-World Effortful Choice Without Corresponding Shifts in Self-Reported Motivation.

Physical inactivity represents a significant public health concern, as many individuals fail to translate intentions to be active into actual behavior. Acute cognitive exertion may worsen this intention-behavior gap by increasing the subjective cost of effortful action. The present study examined whether acute cognitive exertion and fatigue-like vigilance worsening were associated with movement-related motivation and immediate effort-related choice. Forty participants completed a within-subjects, counterbalanced crossover design in which they either completed a 30-minute Stroop session or a passive YouTube-viewing session. Each visit included pre- and post-assessments of state motivation using the Cravings for Rest and Volitional Energy Expenditure (CRAVE) scale and vigilance, indexed by the Psychomotor Vigilance Task (PVT), followed by a covert stair-versus-elevator choice task to test real-world effortful action selection. A priori planned analyses used mixed-effects models appropriate to each outcome, with period and order included as crossover covariates. The Stroop condition produced the expected interference effect, with slower responses and lower accuracy on incongruent than on congruent trials. The Stroop condition yielded greater cognitive fatigue than the YouTube condition as indexed by more lapses on the post-PVT test. CRAVE-REST and CRAVE-MOVE did not exhibit Condition x Time effects, indicating that average self-reported motivation did not shift uniformly by condition. However, primary CRAVE explanatory models showed that increased cognitive fatigue was associated with higher post-task CRAVE-REST and lower post-task CRAVE-MOVE. Participants were less likely to choose the higher-effort stair option after the Stroop condition than after the YouTube condition, however, this was not mediated by cognitive fatigue or subjective movement-related motivation. Together, our findings suggest cognitive exertion produced fatigue-like vigilance disruption that tracked subjective motivation at the individual level, yet neither vigilance nor self-reported motivation statistically accounted for observed shifts in real-world effortful choice. Immediate effort-related decisions appear to shift under cognitive load through processes not captured by standard measures of vigilance or global motivation.