Autism, processing speed, and adaptive functioning in preschool children.

Objectives: To study cognitive test profiles with a focus on processing speed in a representative group of preschool children with autism spectrum disorder (ASD) and relate processing speed to adaptive functioning.
Methods: Cognitive assessments were performed in 190 3.6-6.6-year-old children (164 boys and 26 girls) with ASD, using either Griffiths' developmental scales (n = 77) or the Wechsler Preschool and Primary Scale of Intelligence-Third Edition (WPPSI-III) (n = 113). Cognitive data were related to adaptive functioning as measured by Vineland Adaptive Behavior Scales (VABS).
Results: Cognitive profiles were characterized by low verbal skills. Low processing speed quotients (PSQs) were found in 66 (78%) of the 85 children who were able to participate in the processing speed subtests. Except for Socialization, all VABS domains (Communication, Motor Skills, Daily Living Skills, and Adaptive Behavior Composite scores) correlated significantly with PSQ. Multiple regression analysis showed that PSQ predicted 38%, 35%, 34%, and 37% of the variance for Communication, Daily Living Skills, Motor Skills, and total Adaptive Composite scores, respectively.
Conclusion: Preschool children with ASD had uneven cognitive profiles with low verbal skills, and, relatively, even lower PSQs. Except for Socialization, adaptive functioning was predicted to a considerable degree by PSQ.