Semantic facutation in aphasia: effects of time and expectancy.

Abstract Two auditory lexical decision semantic priming experiments were conducted to examine the extent to which the automaticcontrolled processing dichotomy can characterize lexical access deficits in Broca's and Wernicke's aphasics. In Experiment 1, prime-target predictability was varied while the interval between prime and target (ISI) was held constant. In Experiment 2, ISI was varied while prime-target predictability was held constant. The pattern of semantic facilitation and inhibition results for Experiment 1 showed that Broca's aphasics were influenced by prime-target predictability, whereas Wernicke's aphasics were not. In contrast in hperiment 2, manipulations of ISI at 150 and 2000 msec did not affect patterns of semantic facilitation for either Broca's or Wernicke's aphasics. Taken together, the results of these two experiments suggest that Broca's aphasics use heuristic strategies more so than old and young normal subjects. In addition, they seem to have an automatic processing deficit affecting the level of activation of lexical entries, with a spared time course of activation. Wernicke's aphasics show a pattern of results consistent with the view that automatic processing is unimpaired in these patients, while they fail to use heuristic strategies in these tasks.