Background: Autism, intellectual disability, and specifi c language impairment (SLI) constitute three important forms of developmental disability that are often mistaken for each other, especially in very young children (under age 4). Diagnostic problems are caused by the fact that a fundamental problem
in cognition, language, or behavior has secondary effects on the remaining areas, which makes it diffi cult to separate cause from effect. A wrong or absent diagnosis can be a major hindrance in providing properly targeted therapy for developmentally disabled children.
Material/Methods: From a population of 667 children referred to a specialized outpatient clinic for developmentally disabled children, we identifi ed 35 children in whom the fundamental diagnosis of autism, intellectual
disability, or SLI was unambiguous, and then analyzed these children’s scores on 7 subtests from the Munich Functional Developmental Diagnosis, in order to identify specifi c features of each of the three syndromes.
Results: The most reliable differentiating factor in our research group proved to be the MFDD subtest for self-reliance. A model was constructed to assist in analyzing the complex interactions of symptoms, which frequently overlap.
Conclusions: Cognitive and communicative limitations resulting from underlying perceptual dysfunctions can lead to inappropriate adaptive behavior in children with developmental disorders, such as autism, intellectual disability, and specifi c language impairment. Each of these syndromes has a specifi c
profi le in respect to measures of cognitive function, social skills, and verbal communication.

Keywords: Ambulatory Care Facilities, Autistic Disorder - diagnosis, Child Development Disorders, Pervasive - diagnosis, Child, Preschool, Cognition Disorders - diagnosis, Diagnosis, Differential, Language Development Disorders - diagnosis, Poland