Table 1.

Coding System Used for Studies Included in the Meta-Analysis

Variable	Coding	Description
Design
Type of condition	1 = Observation only
	2 = Execution only
	3 = Observation and execution
Baseline present	0 = No
	1 = Yes
Type of baseline (static vs. dynamic)	1 = Static	If a baseline is present, whether the stimulus is moving or still (e.g., picture of hand versus video of hand movement)
	2 = Dynamic
	5 = No stimulus
Type of baseline (biological vs. nonbiological)	1 = Biological
	2 = Nonbiological
	5 = No stimulus
Type of stimulus observed (biological vs. nonbiological)	1 = Biological (Subcode 1 = of the biological, coded as social; Subcode 2 = coded as nonsocial)	Type of stimulus with which the subjects are presented during observation.
	2 = Nonbiological
	3 = Biological and nonbiological
	5 = Auditory
Type of stimulus observed (dynamic vs. static)	1 = Dynamic	Whether the type of stimulus observed is moving or still
	2 = Static
Type of stimulus observed (live vs. video)	1 = Live
	2 = Video
Object-directed	0 = No
	1 = Yes
Sample characteristics
Sample size (N)	Numerical value	Sample size for which results are reported
Age	1 = 0–4 years
	2 = 5–18 years
	3 = >18 years
Gender	1 = >70% male
	2 = >70% female
	3 = mixed