To study the effects of clinicians' slow rate on the speech of children who stutter with and without a concomitant phonological disorder, an A-B-A-B single case design was used with six clinician-child dyads, where B = Clinician's slow speech rate model. Two boys and one girl, aged 49-54 months, stuttering with disordered phonology (S + DP), were compared to three boys aged 42-50 months, stuttering with normal phonology (S + NP). Articulation rates were measured in phones per second (pps) in clinician-child adjacent utterance pairs. The S + NP dyads showed improved fluency in the B condition through a larger effect size, higher mean baseline stutter reductions and lower percentages of non-overlapping data than did the S + DP dyads. The S + DP girl showed relatively improved fluency in the B condition. S + DP children showed no articulation rate alignment (Range: 16% decrease to a 1.2% increase), whereas S + NP children averaged a 20% pps rate reduction (Range: 19.6-25.4% decrease), aligning with their clinicians who averaged a 38% pps rate reduction from baseline. The S + DP group spoke significantly (z = -4.63; p < 0.00) slower at baseline (Mdn = 6.9 pps; SE = 0.07 pps) than S + NP children in previously published samples (Mdn = 9.8 pps; SE = 0.22 pps). Results suggest that a slow rate model alone is not effective for facilitating fluency in S + DP boys with time since onset of about 2 years.
Keywords: Articulation rate; children who stutter; dyadic gap; single-subject design; treatment efficacy.