The Effect of Response-Code on Stroop Interference and Facilitation

The present study examined how manual response-code mappings shape Stroop interference and facilitation in the manual Stroop task. Previous research has extensively compared manual and vocal responses, but less is known about whether different types of manual response-codes alter performance within the manual response modality. A final sample of 158 participants completed a color-word Stroop task in 1 of 5 response-code groups: color-keys, in which colored stickers appeared on the keyboard; word-keys, in which color-word stickers appeared on the keyboard; color-cues, in which colored patches appeared on the screen; word-cues, in which color-words appeared on the screen; and no-label, in which participants responded using the same keys without response labels. Results showed that Stroop interference was larger when response-codes were presented on the screen than on the keyboard, suggesting that on-screen cues may increase within-display competition and/or provide less stable support for maintaining response mappings. In addition, word-codes produced greater interference than color-codes regardless of their location, consistent with translational models and the verbal mediation hypothesis. Finally, the no-label condition produced the largest interference, indicating that response labels can support performance by reducing the internal demands of maintaining stimulus-response mappings. Facilitation did not differ reliably across response-code groups. These findings highlight the importance of considering response-code mapping as a meaningful design factor in manual Stroop tasks.