Developmental disfluency in 2-, 4-, and 6-year-old boys in neutral and stress situations.

Disfluency characteristics of 36 nonstuttering boys aged 2, 4, and 6 were analyzed from tape-recorded speech samples made during free play within neutral and stress situations. Comparisons of frequency of disfluency were made among the different ages within each situation. In the neutral situation, 2-year-olds had significantly higher disfluency frequencies than either 4- or 6-year-olds for word repetitions and phrase repetitions; 2-year-olds also had a higher frequency of disrhythmic phonations than 6-year-olds but not than 4-year-olds. In the stress situation, 2-year-olds had a higher frequency of average oscillation (number of repetitions per instance of disfluency) than either 4- or 6-year-olds and a higher frequency of disrhythmic phonations than 6-year-olds. Comparisons of frequency of disfluency were also made between the neutral and stress situations. The only statistically significant differences were for word repetitions and phrase repetitions for 2-year-olds, with higher means for the neutral situation.