Objectives: This study aimed to replicate and extend findings concerning the performance of autistic individuals on RPM in a population of strictly (rather than clinically) defined Asperger children and adults.
Methods: The child sample included 23 Asperger and 24 typically developing children, matched on age (6 to 16 years old). The adult sample included 29 Asperger and 19 control adults, matched on age (16 to 49 years old). An Asperger diagnosis was given for participants eligible for an autism diagnosis on ADI-R or ADOS (module 3 or 4), but who did not have delayed speech, echolalia, pronoun reversal, or stereotyped speech, all as defined in the ADI-R. All participants completed the standard version of RPM. In addition, children completed the Wechsler Intelligence Scale for Children (WISC-III), whereas adults completed the Wechsler Adult Intelligence Scale (WAIS-III). The three instruments were administered by clinicians unaware of the hypotheses of this study.
Results: Asperger children obtained on average a Wechsler Full-Scale IQ at the 48th percentile and a RPM score at the 60th percentile. Planned one-way analyses of variance revealed a significantly higher RPM performance than Wechsler FSIQ performance by the Asperger children, but no difference between performance on the two tests by the control children (Wechsler FSIQ 70th percentile and RPM at 72nd percentile). Similarly, Asperger adults scored significantly higher on RPM (75th percentile) than on the Wechsler FSIQ (49th percentile), whereas there was no significant difference between performance on RPM (82nd percentile) and Wechsler FSIQ (75th percentile) for the control adults.
Conclusions: These findings demonstrate that, while differing from autistics in history of speech delay and in individually having Wechsler scores in the normal range (here with group averages near the 50th percentile for children and adults), Asperger children and adults are similar to autistic children and adults in presenting with significantly higher RPM than Wechsler scores. These findings suggest that strengths in RPM performance and therefore in fluid reasoning are pervasive across the autistic spectrum.