Evidence for the extinction burst in grip force: A preregistered study

In behavioral science, "extinction" refers to the change that follows when a previously rewarded pursuit no longer yields reward; accordingly, this phenomenon is central to behavioral reorganization across species. Although one might expect a monotonic transition from engagement to disengagement in goal-directed behavior, in mammals this transition is often non-monotonic: behavior can transiently intensify before declining--a phenomenon known as the "extinction burst." Detecting this effect requires a metric and time window that capture the transient, non-monotonic change and enable comparison to counterfactual continued-reward performance. We preregistered a study in which participants earned money by producing grip-force responses on a hand dynamometer. Peak standardized force in short, time-matched blocks was pre-specified as the primary index; analyses contrasted before-to-after change at different tiers where extinction was present versus absent. Mixed-effects models pooled within-participant contrasts while controlling for the secular trend across blocks. Peak force increased upon extinction onset, yielding a large and robust stage-by-treatment interaction effect. Exploratory analyses showed changes in response rate, minimum idle force, response duration, and force variability throughout extinction. We highlight that the extinction burst is better conceived as a before-after contrast at reward[->]extinction transitions, benchmarked against matched reward[->]reward transitions, rather than a raw post-onset elevation.