Validity of the construct of nonverbal memory: A factor-analytic study in a normal elderly sample

One problem in evaluating the construct of nonverbal memory is finding a purely nonverbal memory measure. Encouraged by initial research with a new measure, the Visual Spatial Learning Test (VSLT), we examined nonverbal memory in a normal elderly sample. Subjects were 460 community-dwelling individuals between the ages of 55-95. All received neuropsychological batteries which included the Wechsler Adult Intelligence Scale-Revised, the Wechsler Memory Scale-Revised, the Rey Auditory Verbal Learning Test, and the VSLT. Two variable sets were created to avoid overlapping immediate and delayed recall trials for the same stimulus materials. Exploratory factor analyses using two different extraction methods were performed. Across analyses a single general memory factor was observed, no modality or time specific factors were found. If it can be assumed that we used adequate measures of nonverbal memory, our results combine with prior research to challenge the validity of the construct of nonverbal memory as distinct from verbal memory, especially in older normal adult populations.