Similarities and differences between psychological deficit in aging and brain damage.

This study compared education matched young brain-damaged, young nonbrain-damaged, old brain-damaged and old nonbrain-damaged groups on a battery of measures of cognitive, perceptual, and motor skills. By means of a factor analysis, the 26 original measures were reduced to four, called nonverbal memory, language ability, motor ability, and psychomotor problem solving. Factor scores were obtained for each of these measures and were subjected to a linear discriminant analysis; 48.3% of the cases were correctly classified. Plotting of the canonical variable suggested that the first discriminant function separated the young nonbrain-damaged group from the others, but did not discriminate well otherwise. The second discriminant function was noncontributory. Multi-variate analysis of variance produced significant main effects for the "age" and "brain damage" factors, but the interaction term was nonsignificant. Inspection of the cell means indicated that the four measures interacted differentially with age.