Interpreting results of the fluent speech paradigm in stuttering research: difficulties in separating cause from effect.

This paper examines difficulties inherent in interpreting results of studies that compare the fluent speech characteristics of stutterers and nonstutterers. The majority of these studies have reported stutterer/nonstutterer differences in temporal parameters of fluent speech production. Such differences have been interpreted as indicating that stutterers possess temporal-motor deficits that are ever-present in speech and, therefore, causal to stuttering. However, a problem for researchers studying the fluent speech of stutterers is that samples may be contaminated by the influence of stuttering. In this paper, evidence is reviewed which suggests that characteristics of the perceptually fluent speech of stutterers change as a function of a number of variables: (a) context of experimental samples, (b) treatment history of subjects, (c) stuttering severity of subjects, and (d) developmental history of stuttering. In addition, evidence is presented which can be interpreted to show that each of these variables reflect stuttering, either directly or indirectly. It is argued that because these variables are difficult to fully control, or account for, comparison of the characteristics of the perceptually fluent speech of stutters and nonstutterers as a method of studying stuttering causation is problematic. Alternative directions for research activity are discussed.