Picture Exchange Communication System (PECS): PECS is an alternative communication system that uses picture symbols. It is taught in six phases starting with a simple exchange of a picture symbol for a desired item. Individuals learn to use picture symbols to construct complete sentences, initiate communication, and answer direct questions.

Perseveration: Repetitive movement or speech, or sticking to one idea or task, which has a compulsive quality to it.

Pervasive Developmental Disorder - Not Otherwise Specified (PDD-NOS): The diagnosis given for children who present with some of the characteristics of either Autism or Asperger's Syndrome, but not severe enough for a diagnosis of either of these conditions.

Pivotal Response Training: An intervention based on the principles of applied behavior analysis (ABA). Two pivotal behaviors, motivation and responsivity to multiple cues are taught. These behaviors are central to a wide area of functioning and positive changes in these behaviors should have widespread effects.

Positive Behavior Supports: The broad enterprise of helping people develop and engage in adaptive, socially desirable behaviors and overcome patterns of destructive and stigmatizing responding.

Relationship Development Intervention (RDI): a parent-based intervention program where parents are provided the tools to effectively teach Dynamic Intelligence skills and motivation to their child.