Semantic category and rhyming processing in the left and right cerebral hemisphere.

In this study, the question of hemispheric abilities in processing explicit semantic and phonological information was addressed by measuring response latencies and performances in two judgement tasks. In the semantic task, word pairs were sequentially presented to the left or right visual field and subjects were asked to judge whether these words were categorically related or not. In the phonological task, the same subjects were asked to decide whether pairs of orthographically dissimilar words rhymed or not. Statistical analysis showed that reaction times (RT) were significantly shorter in both tasks when words were presented to the right visual field. Furthermore, in the semantic task, faster responses were observed in both visual fields when the words were related than when they were unrelated. This response facilitation tended to be stronger when words were presented to the left visual field. This result is in accordance with other results obtained by lexical decision studies showing that priming in the right hemisphere is due to controlled processing. By contrast, RT differences between rhyming and non-rhyming word pairs in the phonological task did not reach significance. This supports previous findings showing that phonological facilitation cannot occur when orthographic and phonological indices are in conflict.