Definition of pervasive developmental disorder: any group of disorders of infancy, childhood or adolescence characterized by distortions in the development of basic psychological functions such as language, social skills, attention, perception, reality testing and movement. http://dictionary.reference.com/browse/pervasivedevelopmentaldisorderPervasive developmental disorder was first used in the 1980s to describe this class of neurological disorders that can impair social and communication skills and repetitive behaviors. PDD itself is not actually a disorder. It's a description. It is somewhat of a collection of multiple disorders that can spread through a series of impairments in social interactions, verbal and nonverbal communications, and stereotyped behavior patterns. There is much variability in the symptoms and severity of these disorders among individuals. This is why multiple disorders fall under this label. Disorders that fall into the PDD category are Asperger syndrome, Rett syndrome, autistic disorder, childhood disintegrative disorder, and pervasive developmental disorder-unspecified (PDD-NOS). Because these disorders have a certain portion of the autism spectrum, PDD is now sometimes referred to as autism spectrum disorder (ASD). This is the term that will be used in the rest of this article. The autism spectrum ranges from least severe to most severe: Less severe autistic disorder Pervasive developmental disorder Asperger syndrome More severe Rett syndrome Childhood disintegrative disorder While communication dysfunction is one of the central features of ASD, its symptom profile varies widely from person to person. At one extreme, there are the children... in the middle of the paper... Journal of Speech, Language, and Hearing Research, 48(5), 1080-1097. Retrieved from EBSCOhost module.Fisher, N., Happe F., & Dunn, J. (2005). The relationship between vocabulary, grammar, and performance on false belief tasks in children with autism spectrum disorders and in children with moderate learning difficulties. Journal of Child Psychology & Psychiatry, 46(4), 409-419. doi:10.1111/j.1469-7610.2004.00371.xSilliman, Er, Diehl, S. F., Bahr, R., Hnath-Chisolm, T., Zenko, C., & Friedman, S. A. (2003). A new look at performance on theory of mind tasks by adolescents with autism spectrum disorder. Speech, language and hearing services in schools, 34(3), 236-252. Retrieved from EBSCOhost.Ral, S. M., & Gagie, B. (2006). Learning through seeing and doing: Visual supports for children with autism. TEACHING Exceptional Children, 38(6), 26-33. EBSCOhost recovered module.