Encoding of frequency of occurrence by aphasia patients: attentional or linguistic deficit?

Frequency-encoding performance of aphasic patients and control subjects was studied in order to test Grober's (1984) hypothesis that aphasic patients are not deficient in the encoding of frequency of events. Experiment 1 compared patients and controls on four types of list: spoken words, visual words, images of objects, and abstract figures. Experiment 2 varied semantic and phonological similarity among the words in one list. Both experiments found differences between the groups, and differences between conditions. The deterioration in patients tended to be greater for linguistic than for nonlinguistic material (experiment 1), and was strongly enhanced by semantic similarity (experiment 2). Results are better explained by a linguistic deficit than by an attentional capacity account of aphasia.