Effects of five experimental treatments of stuttering.

Twenty adult stutterers were exposed to each of five experimental treatments: time-out, noise, delayed auditory feedback (DAF), "wrong" and metronome. In each session a subject spoke for 20 minutes without treatment (baserate) followed by 30 minutes in one of the five experimental conditions. Before the five treatment sessions, subjects accomplished three pre-experimental tasks: expectancy, changeability, and adaptation tasks. Percent stuttering decreased significantly in all conditions, and stuttering duration reduced significantly in all but the noise condition. The amount of reduction in percent stuttering from baserate to treatment (change score) in time-out was positively related to the change scores in DAF and metronome. Change scores in metronome were positively related to change scores in time-out and "wrong." Percent stuttering change scores in noise, DAF, and "wrong" were essentially unrelated. Stuttering duration change scores were related only for the time-out and DAF, and metronome and DAF conditions. In general, the pre-experimental expectancy, changeability, and adaptation scores were unrelated to change scores in any of the experimental conditions. Words spoken per minute did not change significantly from baserate to treatment for any experimental condition except time-out.