Objective: To determine whether subtypes of children with pervasive developmental disorder (PDD) differed on variables that were relatively independent of distinguishing criteria.
Method: Higher-functioning children with PDD, 4 through 6 years of age, were differentiated into those with autism (n = 47) and those with Asperger's syndrome (n = 21) on the basis of delayed and deviant language development. The groups were then compared on a wide range of measures including PDD symptoms, adaptive behaviors in communication, socialization, and activities of daily living, and an assessment of verbal and nonverbal cognitive skills.
Results: Significant differences between the groups existed on many PDD symptoms, adaptive behaviors, and cognitive measures of language competence, but not on aspects of nonverbal communication, nonverbal cognition, or motor development.
Conclusion: Subtypes of children with PDD can be identified that differ on variables relatively independent of defining characteristics. These findings should provide a firm foundation into research to determine whether children with autism and Asperger's syndrome also differ on outcome, etiology, and response to treatment.