Time course of semantic activation in the cerebral hemispheres

Recent visual half-field studies using relatively long stimulus onset asynchronies (SOAs) and non-associated category members (e.g. deer-pony) as word pair stimuli have indicated that with a low proportion of related stimuli, automatic priming of non-associated category information is larger in the right than in the left hemisphere [Chiarello and co-workers]. The present study examined semantic priming of non-associated category members, with a low proportion of related stimuli in the visual fields/hemispheres across SOAs of 165, 250, 500, and 750 msec. Eighty normal, right-handed subjects were tested (20 subjects/SOA). The results revealed a left hemisphere advantage in priming at the 165 msec SOA, whereas the right hemisphere advantage reported in earlier studies was observed at the longest 750 msec SOA only. The results challenge the view that a larger range of related meanings is activated in the right than in the left hemisphere. Rather, the time course of semantic activation may be different in the hemispheres.