| Normal aging is associated with decline in nonverbal (fluid) intelligence whereas controversy exists as to whether or not aphasia produces intellectual impairment. This study examined the effects of aging and aphasia on fluid intelligence using the Raven's Coloured Progressive Matrices and the Cattell Culture Fair Intelligence Tests. Normal aged adults and aged left-hemisphere-damaged aphasics were studied to determine whether verbal deficits caused by aphasia would impair nonverbal intellectual performance in elderly aphasics. In addition, this study investigated whether there were differences in fluid intelligence between normals and aphasics with anterior and posterior lesions.;Forty-five middle-aged and elderly aphasics were studied with two lesion groups (anterior and posterior) in each age grouping. Performance was compared with 24 age-matched normals. The Boston Diagnostic Aphasia Examination confirmed aphasia type, severity level and ruled out constructional apraxia. A two-way analysis of covariance with concomitant variables of education, occupation and sex was performed.;A significant age effect was found on all measures of fluid intelligence. The order of responses from best to worst by age and aphasia group was: middle-aged normals, old normals, middle-aged aphasics, old aphasics. This pattern differed on a few items where the order was middle-aged normals, middle-aged aphasics, old normals, old aphasics. When age was divided into three groups, (1) 45 to 55, (2) 65 to 74, (3) 75 to 85; group three performed less well than group two.;Performance of all aphasics was significantly different from normals. Increasing the severity level of aphasia significantly decreased intellectual performance, but type of aphasia was not found to affect cognition. The existence of aphasia depressed nonverbal intellectual performance more than that expected on the basis of age alone. This study supports the viewpoint that aphasia produces a generalized deficit in nonverbal intelligence which cannot be easily separated from a language disturbance. It does not support the view that fluid intelligence is a right-hemisphere function. Location of lesion was not an adequate indicator of cognitive impairment. Rather, the effect of age, coupled with brain damage, appeared to be the most cogent predictor of intellectual performance. |
