Table 5 Operational Definitions of Social Initiation Behavior and Social Response Behavior

	Operational Definitions	Examples	Non-examples
Social Initiation Behavior	Verbal and non-verbal behaviors displayed by the participant in a situation where no vocal or gestural behavior has occurred from others within the preceding 3 seconds.	• Bringing and showing a toy.• Tapping a peer’s shoulder to initiate conversation or draw attention.• Leading by the hand toward a toy.• Requesting play or asking a new question.• Vocalizing while making eye contact with a peer.	• Problem behaviors (e.g., screaming, crying, throwing toys, hitting others, escaping).• Solitary play.
Social Response Behavior	Verbal and non-verbal response behaviors displayed by the participant within 3 seconds after a vocal or gestural behavior has occurred from others.	• Receiving a requested toy.• Following the gaze to a location requested by others.• Imitating.• Responding with facial expressions.• Gestures such as nodding to a question.• Questions like “Yeah?” or “What did you say?	• Repetitive self-stimulatory behaviors (e.g., echolalia, self-talk).• Problem behaviors (e.g., verbal/ non-verbal protest, crying, vocalizations or behaviors unrelated to the context).