Can Stuttering on Content Versus Function Words Predict Stuttering Persistence in Young Children?

The widely cited shift from function to content word stuttering is based largely on cross-sectional studies using broad binary word-class distinctions, which may obscure group differences. This study tested whether the distribution of stuttering-like disfluencies (SLDs) by finer grained part-of-speech-defined grammatical categories and utterance position distinguishes children who persist in stuttering (CWSP) from those who recover (CWSR) and whether alternative measurement definitions offer insight beyond the traditional function/content dichotomy.

Spontaneous language samples were drawn from 57 children (12 CWSP, 45 CWSR) in the Illinois International Stuttering Research Project at three time points across 3 years postonset. SLDs were identified and analyzed by binary lexical class (content vs. function), part-of-speech-defined grammatical categories, and utterance position (initial, medial, final) using Computerized Language Analysis tools. Statistical analyses included repeated-measures analysis of variance, mixed-effects modeling, and Firth logistic regression.

Children stuttered more frequently on function words than content words across groups and time points. The combined influence of grammatical class and utterance position yielded the clearest differentiation between groups. Utterance-final disfluencies were more strongly associated with persistent stuttering, whereas variation in metric definition (tendency vs. occurrence) reflected different analytic perspectives without altering the overall pattern of results or differentiating recovery outcomes.

While the content/function distinction captures general stuttering patterns in early childhood, it does not differentiate recovery status. Analyses incorporating utterance position and explicit measurement definitions reveal that fluency breakdowns are best understood as emerging from structural and positional pressures within the utterance rather than from categorical word-type effects. These findings highlight the value of moving beyond coarse word-class divisions to better characterize variability in early stuttering and to support more precise, linguistically informed models of fluency development.