Table 2.

Coding Definitions for Video‐Coded Language Variables

Language opportunities	Number of language opportunities provided by the parent, including direct prompt (i.e., a verbal model), indirect prompt (i.e., “ready, set…”), or time delay (parent holds up the object of interest and waits expectantly for a vocal response). Reported as rate/minute.
Responsivity	Proportion of appropriate child vocal responses, following a parental prompt (reported as %; see Inappropriate Responses for exclusionary examples).
Inappropriate responses	Proportion of child nonfunctional, noncommunicative, echolalic, out of context, inappropriate, undirected, or disruptive responses to parent prompts.
Initiations	Number of child‐initiated functional, appropriate vocalizations (rate/min).
Functional vocal utterances (FVU)	Composite measure of the overall number of functional/meaningful, task‐directed, and purposeful vocalizations with appropriate volume and directedness to person or activity (including both initiations and appropriate vocal responses). Reported as rate/minute.