The Differential Contribution of the Verbal Code in the Course of Visual Learning: Evidence from Hemisphere-Damaged Patients

Control patients and patients with hemispheric lesion were given a paired-associate memory test made up of meaningful figures and their performance was compared on two measures: number of errors over the first three trials and trials to criterion. Impairment on the former measure was associated with left brain damage and found to be related to the degree of aphasic deficit, suggesting the involvement of the verbal code in the early stages of the learning process. However, analysis of trials to criterion showed that a defective performance was confined to patients of either hemispheric group having posterior lesions and bore non relationship to measures of language impairment. It is inferred that, as the learning process consolidates, the aid provided by verbal mediation to recognizing visual images progressively recedes.