Stuttering on function and content words across age groups of German speakers who stutter.

Recent research into stuttering in English has shown that function word disfluency decreases with age whereas content words disfluency increases. Also function words that precede a content word are significantly more likely to be stuttered than those that follow content words (Au-Yeung, Howell and Pilgrim, 1998; Howell, Au-Yeung and Sackin, 1999). These studies have used the concept of the phonological word as a means of investigating these phenomena. Phonological words help to determine the position of function words relative to content words and to establish the origin of the patterns of disfluency with respect to these two word classes. The current investigation analysed German speech for similar patterns. German contains many long compound nouns; on this basis, German content words are more complex than English ones. Thus, the patterns of disfluency within phonological words may differ between German and English. Results indicated three main findings. Function words that occupy an early position in a PW have higher rates of disfluency than those that occur later in a PW, this being most apparent for the youngest speakers. Second, function words that precede the content word in a PW have higher rates of disfluency than those that follow the content word. Third, young speakers exhibit high rates of disfluency on function words, but this drops off with age and, correspondingly, disfluency rate on content words increases. The patterns within phonological words may be general to German and English and can be accounted for by the EXPLAN model, assuming lexical class operates equivalently across these languages or that lexical categories contain some common characteristic that is associated with fluency across the languages.