The psychometric structure of the Wechsler Memory Scale in comparison to the WAIS-R in a low-IQ clinical population.

The psychometric structure of the Wechsler Memory Scale (WMS) and its relationship to the revised Wechsler Adult Intelligence Scale (WAIS-R) were studied in an outpatient population of 103 individuals with low Full Scale IQ scores (M = 71). We found that the age correction of the WMS scores gave memory quotients (WMQ) equivalent to WAIS-R FSIQ scores, but our findings also raised problems of interpretation. If the usual rule of thumb of a 12-point discrepancy between the MQ and the FSIQ were applied, the WMS might be relatively insensitive to memory impairment in this low-IQ clinical population, in which more numerous cases of impairment could be expected. Principal components analysis of the WMS raw scores and three WAIS-R scores included as reference variables yielded five orthogonal factors: Attention/Concentration; Visual Reproductions; New Verbal Learning; Well-learned Semantic Knowledge; and Intelligence. We argue that raw scores on the WMS should be reported to optimize possible diagnostic specificity and to align the WMS with experimental and clinical research in various types of memory functioning and impairment.