Examining the time course of prime effects on Stroop processing.

This study was conducted to assess the effect of priming on the Stroop task over time. Color-congruent, color-incongruent, and neutral stimuli were randomly presented. Five prime conditions were also used. The prime conditions included valid color, invalid color, valid word, and invalid word primes and no prime. Primes were presented to 8 subjects at varying stimulus onset asynchronies ranging from -200 msec., i.e., 200 msec, before the color-word stimulus, to 200 msec, i.e., 200 msec, after the color-word stimulus. Analysis suggested the facilitory or inhibitory effects of semantic information on the Stroop task are reduced when the prime follows the color-word stimulus by 200 msec. This implies 200 msec. are needed to make the proper color response. A model is proposed to account for the findings. Methodological considerations for studies using priming and the Stroop task are also discussed.