Table 2.

Strategies included on the NDBI-Fi.

Strategy	Description
Behavioral strategoes
Communication temptations	The SLP elicits child communication by arranging the environment, such as violating their expectations in a familiar routine, putting desired objects out of reach, or giving them toys that require assistance to operate. They should wait for the child to respond to the elicitation episode and may initiate a direct teaching episode if the child does not respond with the targeted skill.
Frequency of direct teaching	The SLP encourages the child to use a targeted skill using some sort of verbal prompt (e.g., say prompts, open questions, choice questions). Prompts must include instruction from the SLP, a child response, and reinforcement from the SLP to be considered a direct teaching episode.
Quality of direct teaching	Direct teaching episodes (a) are clear, (b) elicit a communication skill at or just above the child's developmental level, (c) are used when the child is motivated and interested in the object/action for which the SLP is prompting, (d) include scaffolding to support a correct response if the child does not initially respond with the prompted skill, and (e) end with the provision of reinforcement that is natural and appropriate to the activity.
Developmental strategies
Face-to-face and on the child's level	The SLP is facing the child at a similar level within the child's line of sight. Toys and objects should be between the SLP and the child when possible.
Follow the child's lead	The child chooses activities, how long to stay in each activity, and how to play during each activity, with the SLP having an active role and honoring the child's interests and disinterests. The SLP may provide options for new activities/play actions but does not force the child to follow along.
Positive affect and animation	The SLP uses an upbeat and encouraging tone, facial expressions, and overall affect matched to the child's sensory and engagement needs.
Modeling appropriate language	The SLP uses utterances at or just above the child's developmental level and limits their use of questions and directions. Language should be topically contingent to the child's focus of attention.
Responding to child communication	The SLP responds to the child's communication attempts in a timely manner. They should respond to all forms of communication (e.g., vocalizations, words, gestures, eye gaze) and treat this communication as meaningful. If the child is not communicating, the SLP should imitate the child's actions and label them with topically contingent comments.
Pace of verbal models a	The SLP pauses between conversational turns to allow the child an opportunity to communicate, waiting at least 3 s before taking another verbal turn.

Note. NDBI-Fi = Naturalistic Developmental Behavioral Intervention–Fidelity Rating Scale (Frost et al., 2020); SLP = speech-language pathologist.

^aItem added in Sone et al. (2021).