Table 2.

Operational Definitions of Observational Codes

Code	Definition	Examples
Higher-order Supported Joint Engagement (HSJE)	The caregiver and child are engaged with the same materials, and the caregiver’s actions influence the child’s play. The child does not visually reference the adult. The child reciprocates the adult’s play actions or collaborates with the adult in a play scheme.	Turn taking sequences (e.g., taking turns placing puzzle pieces on a board), child imitating caregiver (e.g., caregiver makes a toy pig drink water, child makes a toy cow drink water), or the child following through on a verbal directive made by the caregiver.
Supported Joint Engagement (SJE)	The caregiver and child are engaged with the same materials, and the caregiver’s actions influence the child’s play. The child does not visually reference the adult. Includes instances when the child does and does not reciprocate the adult’s play actions/collaborate with the adult in a play scheme.	The HSJE examples above, plus the following: the child and caregiver both play with stacking blocks. The child must adapt their play to accommodate the caregiver’s selection and positioning of blocks, but there is no established turn taking.
Coordinated Joint Engagement (CJE)	The caregiver and child are engaged with the same materials, and the caregiver’s actions influence the child’s play. The child visually references the adult during the interaction.	The child and caregiver take turns stacking blocks, and the child looks to the caregiver after stacking each block and smiles.
Follow-in Talk (FI)	The caregiver provides linguistic input that is related to the child’s current focus of attention, either by describing what the child is looking at or playing with, or making a suggestion about how the child could play with the toy.	The child plays with a toy boat, and the caregiver says, “Look at the boat rocking in the water!” Or, the child plays with a baby doll, and the caregiver says, “Can the baby drink the bottle?”