A consistent result in the evaluation of group-delivered intervention to promote social reciprocity in children with PDDs is that outcome data are inconclusive. Lack of robust evidence of efficacy confounds understanding of these interventions and their value to the field. It is conceivable that the construct of impaired social reciprocity in PDD presents unique circumstances that require special consideration when evaluating the evidence base. Social reciprocity and impairment in social functioning are complex constructs, which require a multi-dimensional, multi-method approach to intervention and measurement of gains. The existing paradigm for evaluating the evidence base of intervention may need modification to permit a more intricate analysis of the extant research, and increase the sophistication of future research.