Concept formation in non-verbal categorization tasks in brain-damaged patients with and without aphasia

The study of thinking in patients with aphasic language impairments has long since been considered as means for learning about neuropsychological processes. In the present investigation, a non-verbal categorization task was used, requiring the subjects to sort several common objects according to different principles. The experimental group consisted of aphasic patients with motor and sensory aphasia. Two control groups were used, one consisting of normal subjects and the other of non-aphasic patients with injuries in the right hemisphere of the brain. The sorting behaviour was analysed according to several aspects. The final product of the categorization was assessed, as well as the behavioural processes observed during the sorting. The results were expressed in terms of different conceptual levels achieved. The results of the investigation showed that the aphasics were significantly inferior to normal controls both quantitatively and qualitatively in all sorting aspects. Possible mechanisms underlying the deficiencies in the sorting behaviour of the two aphasic groups were discussed.