Approaches to Speech-Language Intervention and the True Believer (Letter to the Editor‪)‬

Treatment approaches in speech-language therapy are sometimes selected and justified on the basis of a clinician's experience that "it works." Moreover, it has been argued (e.g., Kamhi, 1999) that such clinical judgment is, in principle, sound and should be endorsed. Contrary to this view; five extraneous effects are presented as confounding influences that invalidate clinical judgment as the sole basis for adopting a therapy approach. Clinicians should always question whether observed changes in their patients are due to their interventions or to extraneous effects. Possible controls for these effects are double-blind and single subject repeated measures. Research design suggestions are presented, with descriptions of the five extraneous effects. **********