Age‐Related Differences in Response Time Across Adolescence Reflect Premotor, but Not Motor, Processing Speed

= 1.73) completed a flanker task while EEG was recorded. We quantified the lateralized readiness potential (LRP) to fractionate RTs into premotor (stimulus-locked LRP S-LRP) and motor (response-locked LRP R-LRP) intervals. Both S-LRP and R-LRP latencies correlated with RT, but only S-LRP latency decreased with age. Mediation analysis confirmed a significant indirect effect of age on RT through S-LRP latency but not R-LRP latency, suggesting that faster processing speed among older adolescents stems from faster premotor-but not motor-processing. We demonstrate the utility of using LRP latencies to investigate domain-specific processing speed, highlighting directions for future work to link structural development research to functional measurements.