A word in the hand is worth two in the push: Comparing vocal and manual responses to the arrow-word Stroop task

The traditional arrow-word Stroop task measures inhibitory control by assessing the slowing of vocal responses to arrow direction in the presence of an incongruent word (e.g., ‘LEFT’ on a right-pointing arrow) compared to an arrow alone. However, it is unclear whether similar interference effects occur for manual responses. Thirty-two healthy adults (18 – 52 years, 22 female) completed two Stroop variants: Task A measured manual left or right button presses, and Task B measured vocal “left” or “right” responses. Each Task included Pure (100% congruent, or incongruent trials), Mixed (70% congruent/30% incongruent trials), and Baseline (100% arrow-only or 100% word-only trials) blocks. Manual responses were faster to arrows than words, and incongruent arrows further slowed responses to words. Yet, the presence of any word slowed manual responses to arrows. Vocal responses showed a different pattern – faster to words than arrows, and incongruent words slowed responses to arrows, but arrows did not affect word responses. For both tasks, interference effects were stronger when congruent and incongruent trials were interleaved in Mixed blocks. The manual Stroop task is a robust measure of inhibitory control, demonstrating the interaction of two sources of interference: automatic word processing and cross-domain translation between spatial and language representations.