A Method for Defining the CORE of a Psychosocial Intervention to Guide Adaptation in Practice: Reciprocal Imitation Teaching as a Case Example

Defining the central components of an intervention is critical for balancing fidelity with flexible implementation in both research settings and community practice. Implementation scientists distinguish an intervention's essential components (thought to cause clinical change) and adaptable periphery (recommended, but not necessary). While implementing core components with fidelity may be essential for effectiveness, requiring fidelity to the adaptable periphery may stifle innovation critical for personalizing care and achieving successful community implementation. No systematic method exists for defining essential components a priori. We present the CORE (COmponents & Rationales for Effectiveness) Fidelity Method--a novel method for defining key components of evidence-based interventions--and apply it to a case example of reciprocal imitation teaching, a parent-implemented social communication intervention. The CORE Fidelity Method involves three steps: (1) gathering information from published and unpublished materials; (2) synthesizing information, including empirical and hypothesized causal explanations of component effectiveness; and (3) drafting a CORE model and ensuring its ongoing use in implementation efforts. Benefits of this method include: (1) ensuring alignment between intervention and fidelity materials; (2) clarifying the scope of the adaptable periphery to optimize implementation; and (3) hypothesizing--and later, empirically validating--the intervention's active ingredients and their associated mechanisms of change.