Strategies of semantic categorization in the cerebral hemispheres

Strategies of semantic categorization in intact cerebral hemispheres were s tudied in two experiments by presenting names of typical and atypical categ ory instances to the left visual field (LVF) (right hemisphere) or to the r ight visual field (RVF) (left hemisphere). The results revealed that the ty picality of instances had a large effect on categorization times in the LVF in both experiments, suggesting that the right hemisphere relies strongly on a holistic, similarity-based comparison strategy. In Experiment 1, the t ypicality effect was weaker in the RVF than in the LVF. In Experiment 2, a typicality effect in the RVF was observed for the "four-footed animal" cate gory but not for the ''bird'' category. The hypothesis that the left hemisp here employs a strategy based on defining or necessary features is not supp orted by the observed typicality effect in the "four-footed animal" categor y. Instead, it is suggested that the left hemisphere may be able to categor ize on the basis of prestored instance-category knowledge. When such knowle dge is not available (e.g., as for four-footed animals), a similarity-based comparison strategy is employed by the left hemisphere, (C) 1999 Academic Press.