Foveal and parafoveal processing of asynchronous Stroop stimuli.

Two experiments are presented which used a form of the Stroop colour-word task to study the processing of target and distractor information under changing conditions of temporal and spatial proximity. Experiment 1 focused on the marked empirical discrepancies in previous research reported in the recent literature. A coloured target and a distractor (neutral, facilitative or interfering) that were separated by variable onset asynchronies were presented foveally to observers. The findings of this study indicate strong distractor effects on response latency at the intermediate stimulus onset asynchronies (SOAs) (around 0 ms) and a clear monotonic decrease in reaction time for colour naming at extreme positive and negative SOAs. Experiment 2 used this same task but presented targets parafoveally and distractors foveally. This manipulation resulted in the same general pattern of processing as found in Expt 1. In addition, a laterality effect was found when the target and distractor were incongruent; the left visual field/right hemisphere showed significantly greater interference as indicated by longer reaction times. These results are discussed in terms of current models of information processing of compound stimuli.