Some Effects Of Stimulus Presentation Rate and Complexity on Perception and Retention in Brain-Damaged Patients

Abstract

The short term memory recall performance of 36 brain-damaged subjects was compared with the performances of 36 mentally retarded subjects and 36 normal control subjects for both total responses correct and for order errors. Stimuli were presented to all subjects at three rates, 40, 60 and 120 significant units per minute, and at three levels of stimulus concept complexity, simple, compound, and complex, at each rate. While the brain-damaged subjects perform at a slightly lower level than normal control subjects, the pattern of their performance was similar to that of the control group and showed significant differences from the performance patterns of the mentally retarded group. The brain-damaged group did not make significantly more order errors than the normal control subjects, suggesting that their organization processes for stimuli icould “keep up” with the input of their reception processes. This was not true for the retarded who made significantly more order errors than both braindamaged and normal subjects under all conditions. A comparison of small groups of left and right hemisphere damaged subjects disclosed no differences in their ability to recall aurally perceived verbal material. The incidence of order errors was not related to Verbal IQ. Correlations were made of scores obtained from subjects on a memory test for visually perceived designs and the incidence of mirror-image errors with verbal memory and verbal order error scores. Mirror-image error scores were significantly and positively related to verbal order scores for the right hemisphere damaged subjects. This relationship did not exist between the scores for the left hemisphere damaged subjects.