Comparability of WAIS--R Digit Symbol and the Symbol Digit Modalities Test.

100 persons referred for neuropsychological evaluation were administered both the Symbol Digit Modalities Test and the WAIS--R Digit Symbol subtest. The two sets of scores correlated 0.85, but standard scores derived from the Symbol Digit Modalities Test were significantly lower than standard scores based on Digit Symbol. The mean score on the former for these subjects is the equivalent of 2 1/2 to 3 WAIS--R age-scaled score points lower than the respective Digit Symbol mean.