For the purposes of this brief, we use the term core components to refer to the essential functions or principles, and associated elements and intervention activities (e.g., active ingredients, behavioral kernels; Embry, 2004) that are judged necessary to produce desired outcomes. Core components are directly related to a program's theory of change, which proposes the mechanisms by which an intervention or program works. The core components are intended to, or have been demonstrated through research to, positively impact the proximal outcomes that address the identified needs and that increase the likelihood that longer-term outcomes will be achieved. In short, the core components are the features that define an effective program.
Core components can be cast as theory-driven, empirically derived principles and then further operationalized as the contextual factors, structural elements, and intervention practices that are aligned with these principles. For example Multi-Systemic Therapy details nine such principles, such as, "Interventions should be present-focused and action-oriented, targeting specific and well-defined problems" (Henggeler, Schoenwald, Liao, Letourneau & Edwards, 2002, p. 157). Multidimensional Treatment Foster Care articulates four such principles, such as, "providing the youth with a consistent reinforcing environment where he or she is mentored and encouraged" (Chamberlain, P., 2003, p. 304). Incredible Years posits social learning principles as core elements of the various school and parent training programs (e.g., Webster-Stratton & Herman, 2010). Sexton and Alexander (2002), surveyed the qualitative and meta-analytic reviews of research related to family-based interventions in the context of Principles of Empirically Supported Interventions (PESI), describing how such empirically derived principles can aid in identifying and developing effective treatment approaches as well as research agendas. Core components, cast as principles, inform the specification of contextual aspects of the interventions (e.g., interventions occur in schools or communities, parent and community involvement, interventions occur in families' homes), structural elements (e.g., a low adult/child ratio, the required number and sequence of sessions), and specific intervention practices (e.g., teaching problem-solving and communication skills, practicing social skills, reinforcing appropriate behavior).
Figure 1. Core Components - From Principles to Practices