Stuttering: overt and covert measurement of the speech of treated subjects.

Fifty-six stutterers, four to 34 months after treatment, received an unexpected telephone call from the clinic announcing that their speech was being assessed. At random times before or after that call, they received an unexpected telephone call from a stranger and, unknown to them, stating their speech was recorded and assessed. Two months after these calls, a subgroup (N = 20) was included in an apparent telephone public opinion survey during which their speech was recorded and assessed. There were no significant differences between the mean frequency of stuttering across the three measurement occasions. Covert assessment of speech appears to offer no methodological advantages when assessing the progress of groups.