Functional Communication Training is often used with individuals with developmental disabilities who may exhibit problem behaviors. Ideally, the function of the problem behavior is systematically assessed first. Based on this information, the individual is trained to communicate for their needs / wants [rather than exhibit problem behaviors]. When the treatment is applied systematically based on the function of the behavior, FCT is often successful. A good reference for outcome research with FCT is:
Hagopian, L., Fisher, W., Sullivan, M., Acquisto, J., LeBlanc, L. (1998). Effectiveness of Functional Communication Training with and without Extinction and Punishment: A Summary of 21 Inpatient Cases [in] JOURNAL OF APPLIED BEHAVIOR ANALYSIS, Vol. 31, No.2 pp 211-235