Considering Generality in the Systematic Review and Meta-Analysis of Single-Case Research: A Response to Hitchcock et al.

This paper responds to the commentary provided by Hitchcock et al. (J Behav Educ, 2015) which provides updated information on the procedures for considering the generality of an intervention using the What Works Clearinghouse (WWC) single-case guidelines. The new information provided by Hitchcock et al. is useful and provides insight into the processes and procedures used by the WWC to make practice and policy recommendations. Moreover, the additional information requires the results of the original Maggin et al. (J Behav Educ 23: 287-311, 2014) paper to be updated and the additional attention to these issues is applauded. The Hitchcock et al. commentary also provides an occasion to consider the concept of generality within single-case research and to consider the role systematic reviews can have in documenting the conditions under which a functional relation is and is not likely to be replicated. It is asserted that systematic reviews of single-case research should be used to catalog the universe of replication attempts for a specified functional relation in order to better understand the individuals and contexts under which results can be expected to generalize. This process requires careful examination of both successful and unsuccessful replication attempts and the consideration of descriptive-and functional-level variables. This response will, therefore, provide an overview of the concept of generality from a single-case standpoint, consider the criteria outlined in the Hitchcock et al. commentary from this perspective, and conclude with recommendations and encouragement to the field to address these issues in future systematic reviews of single-case research. The intent is to engender discussion and development in this area with the broader goal of expanding the influence of single-case research within the domains of practice, policy, and research.