Table 3 Brief description of the PDD behavior inventory (PDDBI) domains used

Approach-Withdrawal Problems Dimension – higher domain T-scores indicate greater severity.

Sensory/Perceptual Approach Behaviors – staring at objects, pica, repetitive toy play, hand flapping, etc.

Ritualisms/Resistance to Change – carrying out rituals or indicating dissatisfaction with a change in the environment or routine.

Arousal Regulation Problems – emotional constriction, hyperactivity, sleeping problems, etc.

Specific Fears – fears and anxieties associated with withdrawal from social or asocial stimuli.

Aggressiveness – aggressiveness toward self or others and associated negative mood states.

A measure of inappropriate social interaction (problems reacting to the approaches of others, understanding social conventions, or initiating social interactions) that corrects for non-vocal social communication skills level (the SOCAPP domain described below).

A measure of problems with the child’s semantic/pragmatic understanding (aberrant vocal quality, echolalia, and perseveration) that corrects for expressive language abilities (the EXPRESS domain).

Receptive/Expressive Social Communication Abilities Dimension – higher domain scores indicate increasing levels of competence.

Social Approach Behaviors – non-vocal social communication skills such as paying attention, joint attention, effective use of gesture, imaginative skills, social play skills, imitation skills, etc.

Expressive Language – ability to speak sounds associated with the English language as well as competence with grammar, tone of voice, and conversational pragmatics.

Learning, Memory, and Receptive Language – memory for locations and movement sequences, understanding possessives, prepositions, adverbs, etc.

Autism Composite – a measure of lack of appropriate social communication skills along with repetitive/ritualistic behaviors.