Table 2.

Gestural Action Categories Used in the Present Study

Global Category	Gestural Action	Definition
Non-Social	Hand Shake	Shaking or flapping of hands with no explicit social intent
	Hand Position	Posturing of hand intentionally, such as creating a “d” or an “f” hand (as in American Sign Language)
	Body Rock	Rocking body back-and-forth or bouncing in an upward and downward motion
	Foot Shake	Shaking or flapping of feet with no explicit social intent
Universal Social	Reach	Extension of arm away from body, stretching toward an object, person, or surface
	Point	Extension of index finger while remaining fingers flex into the palm (“d” hand)
	Arm up	Extension of arms and hands in an upward motion toward another person
	Throw	Throwing object to someone
	Push	Pushing object to someone
	Block	Extension of hand or arm to prevent any contact with one’s person by another individual or object
	Touch	Extension of hand and/or arm to gently make contact with another person
Conventional	Clap	Striking palms together repeatedly
	Cover Face	Hand(s) or object (e.g., a blanket or cloth) placed over face to obstruct another’s view of face
	Hand Wave	Movement of hand(s) or entire arm back-and-forth with palms facing away from body
	Head Shake	Shaking head from side to side in a continuous motion

Note. The list is intended to include actions that could conceivably be interpreted as communicative gestures. The list is not complete, but includes all the gestural types actually observed. The terms are drawn partly from literature on ape and human infant gesture.