Constant and progressive time delay procedures for teaching children with autism: a literature review.

A review of 22 empirical studies examining the use of constant (CTD) and progressive (PTD) time delay procedures employed with children with autism frames an indirect analysis of the demographic, procedural, methodological, and outcome parameters of existing research. None of the previous manuscripts compared the two response prompting procedures. This review suggests that the effectiveness of the two procedures is similar on some variables. However, the CTD procedure resulted in more errors to criterion, a greater magnitude of procedural modifications, and in a delayed moment of transfer of stimulus control than in the PTD studies. Conclusions may influence clinical and educational practices and indicate a need for research.