The Performance of Patients with Unilateral Brain Damage on Face Recognition Tasks

Abstract

The purpose of this research was to compare several tests requiring the recognition of unknown faces for their power to discriminate among different groups of patients with unilateral cerebral lesions. These groups were: 1) right brain-damaged patients without visual field defects (N = 31); 2) right brain-damaged patients with visual field defects (N = 19); 3) left brain-damaged patients without visual field defects (N = 50); 4) left brain-damaged patients with visual field defects (N = 14). One part of the investigation was concerned with subtests made up of fragments of faces (eyes, mouth, half-faces). While subtests involving eyes and mouth did not discriminate among the experimental groups, the right brain-damaged patients and the patients with visual field defects scored significantly lower when required to recognize half-faces. In the second part of the investigation the patients' scores on these subtests, and on an additional perceptual test, an immediate memory test and a delayed memory test were analysed together by multivariate analysis. The interaction hemisphere x visual field defects turned out to be significant, and the inspection of the means showed that on each test one group stood apart for its poorer performance—the right brain-damaged group with VFD. No difference was found in the power of the tests to discriminate among the brain-damaged group. Thus, the hypothesis that hemispheric asymmetry in the recognition of unfamiliar faces is enhanced by the introduction of a memory factor is not supported. In the course of the research a patient having clinically obvious prosopagnosia was found. He was severely impaired not only on the unknown faces tests but also on other visual tests requiring the discrimination of complex patterns. These findings support the hypothesis that prosopagnosia represents simply the most prominent aspect of a general visuo-perceptual disturbance.