Pervasive developmental disorders (PDD) are categorized by social and communication deficits as well as behavioral traits. Many people refer to this group as the autism spectrum of disorders. However, a person who has autism has a PDD. A person can have a pervasive developmental disorder and not have autism. The commonly recognized symptoms of pervasive developmental disorders include social interaction deficits. Individuals who fall within a diagnosis of PDD often have great difficulty interacting with others. They avoid contact with other people and they seem to lack empathy for others. This spectrum of disorders includes deficits in the acquisition of language skills. The individuals who have PDD often have great difficulty using and understanding words, body language, facial expressions and gestures. Common behavior traits of individuals who have pervasive developmental disorders include repetitive movements like rocking, hand-flapping and spinning. Many of these individuals are rigid when it comes to everyday activities and they seem obsessed with routine and order. Pervasive developmental disorders include five different types that vary in symptoms and severity.