Table 1. Descriptive contexts in which playback stimuli were recorded.

Category	Description
Giving	Infant gives object to peer or caregiver
Action request	Infant requests an action or object from a caregiver
Protest	Infant vocalises in reaction to an unpleasant event or action
Declarative Pointing	Infant points at an interesting object or event and vocalises
Food requests	Infant is in the presence of food and requests some