Dissociated identity and semantic priming in Broca's aphasia: how controlled processing produces inhibitory semantic priming.

Broca's aphasics performed a lexical decision task in a semantic priming experiment in which the proportion of related words was manipulated with a sufficiently long stimulus onset asynchrony for expectancy-based, strategic processing to operate. The control subjects showed the typical increase in semantic facilitation as relatedness proportion increased. However, the aphasic subjects demonstrated the opposite effect such that inhibitory semantic priming occurred as relatedness proportion increased even though, in a second experiment, these same aphasics showed an increase in facilitatory identity priming as relatedness proportion increased. This striking dissociation of identity and semantic priming for the aphasics was interpreted as supporting the "center-surround" theory (Carr & Dagenbach, 1990), which accounts for the same dissociation found in the normal population under challenging word-recognition conditions.