Social competition shapes motor response execution and inhibition in a Go/NoGo task: Behavioral, signal-detection,...

The present study examined how social competition modulates motor response execution and inhibition using behavioral, signal-detection, and event-related potential measures. Forty-three participants completed a Go/NoGo (GNG) task under social-competition and control conditions while EEG was recorded. Relative to control, social competition shortened Go-trial reaction times (RTs) without reducing accuracy, and greater RT speeding was associated with larger increases in the rated importance of response speed. Competition also increased NoGo commission errors, reflecting reduced Go/NoGo discriminability (lower d') and a more liberal response criterion (C). Neurally, NoGo trials elicited larger N2 and P3 amplitudes than Go trials, whereas competition enhanced both Go-P3 and NoGo-P3 amplitudes without reliably modulating the N2. Go-P3 amplitude, maximal over centro-parietal/parietal sites, was negatively associated with Go RTs in the control condition. Competition-related increases in Go-P3 amplitude were associated with greater Go-RT speeding and statistically mediated the effect of competition on Go RTs, suggesting greater engagement of an stimulus-response (S-R) mapping process that translates task-relevant stimulus features into the appropriate Go-response representation. NoGo-P3 amplitude, maximal over frontocentral/central sites, was not significantly associated with commission errors or d' in the control condition. However, competition-related increases in NoGo-P3 amplitude were associated with increased commission errors and reduced d' and statistically mediated both effects. This pattern suggests that enhanced NoGo-P3 amplitude reflects increased demands for reactive control under a heightened prepotent Go tendency. Overall, social competition preferentially modulated P3-indexed, time-resolved control processes during motor response execution and inhibition, facilitating faster but still accurate motor response execution while impairing response withholding.