This paper reports the results of cognitive, linguistic, and academic assessments in a representative sample of 62 adults with Williams syndrome. The average age of the group was 26 years and their mean full scale IQ was 61. Differences between Verbal and Performance IQ, and between receptive and expressive language skills, were smaller than generally found in studies of children with this condition. However, an examination of subtest scores revealed an almost identical cognitive profile to that found in children. Skills in other areas, such as reading, spelling, arithmetic, and social adaptation remained at a low level, with functioning generally being around a 6–8-year age equivalent. The consistency of reports on intellectual abilities in both child and adult studies of individuals with Williams syndrome lends increased support to the notion of a syndrome specific pattern of cognitive, linguistic, and adaptive functioning.

Abbreviations: BPVS: British Picture Vocabulary Scale; EOWVT: Expressive One Word Vocabulary Test; WAIS-R: Wechsler Adult Intelligence Scale–Revised; WISC (-R): Wechsler Intelligence Scale for Children (Revised); WORD: Wechsler Objective Reading Dimensions (WORD).