Intelligence and left hemisphere disease. The role of aphasia, apraxia and size of lesion.

The Raven Progressive Matrices and four subtests of the Wechsler-Bellevue Performance Scale were given to 173 left hemisphere patients subdivided according to presence/absence, type (fluent/non-fluent) and severity (moderate/severe) of aphasia. Constructive and ideomotor apraxia scores and CT scan data of each subject entered the statistical analysis. Factors significant in producing a low score on Progressive Matrices and Wechsler-Bellevue were presence of aphasia and constructive apraxia. Site and size of lesion per se failed to account for the intelligence scores. The relationship between aphasia, apraxia, intelligence test scores, and CT scan data were discussed in an attempt to clarify the meaning of these low intelligence test scores in aphasics and to assess the underlying roles of the brain lesions in this deficit. It appears that there are a number of methodological difficulties complicating interpretation of the intellectual deficit based on the Progressive Matrices and Wechsler-Bellevue scores, since performance on these tests is adversely affected by both aphasia and apraxia.