Hemispheric differences in matching Stroop-type letter stimuli.

Two experiments are reported in which normal right-handed males and females had to match two Stroop-type letter stimuli, according to either their global level (Experiment 1) or their local level (Experiment 2). Stimulus presentation was sequential with the first letter presented foveally and the second letter presented to either the right visual field (RVF) or the left visual field (LVF). A manual "Same-Different" response was required. In Experiment 1, the left hemisphere (RVF) showed interference from the irrelevant local level features, supporting an analytic processing mechanism, while the right hemisphere (LVF) showed no such effect, supporting a holistic matching mechanism. In Experiment 2, both hemispheres showed interference from the irrelevant global features, with the right showing a non-significant tendency towards a larger Stroop effect.