Individual differences in accentuation boundaries in Dutch

It has been shown that in Dutch a rising or fal1ing pitch movement can unambiguously accent a syllable Sn when the onset of the movement is positioned in an interval starting some tens of milliseconds before the onset of the vowel and ending somewhat before the offset of the vowel of SO' As the start of the movement is gradually shifted to positions later in the syllable, the percept of accentuation gradual1y shifts from syllable Sn to the fol1owing syllable Sn+1' This was shown in experiments with reiterant, resynthesized speech utterances like /.a.a.a.a.a/ and /mamamamama/ in which the position of the onset of rising and falling pitch movements was systematical1y varied, and subjects were asked to indicate which syllable they perceived as accented. In most cases the number of responses "syllable Sn accented" gradually decreases sigmoidally as the onset of the pitch movement starts later, but, in some cases, especially for falls in /.a.a.a.a.a/ stimuli with relatively long silent periods between the vowels, a plateau can be distinguished in the response distribution during which the proportion of responses "syllable Sn accented" does not continue to decrease, but remains constant. In these experiments, every stimulus was presented only twice to each subject, so that no clear response distributions of individual subjects were available, which did not allow for an interpretation of the nature of this plateau. To find out more about the nature of this plateau, response distributions of individual subjects were determined and compared. It is shown that the response distributions of single subjects do not show a plateau. The plateau arises from the fact that some subjects have an early accentuation boundary, while others have a late accentuation boundary. The implications of these findings are discussed.