Rhythmic units and syntactic units in production and perception.

It has been claimed that spoken utterances consist of isochronous rhythmic units (metric feet), lasting from one major stress to the next. A study of 17 specially constructed sentences showed that productions of the same metric foot types have remarkably similar durations. However, there are clear differences in the average duration of different foot types in the same position, and there is neutralization of durational differences in final position. The partial isochrony found in the study leads to two further questions: the influence of syntax on the production of rhythmic units, and the perceptual nature of isochrony. If rhythmic units are independent of syntactic structure, sentences consisting of the same lexical items should have the same temporal structure regardless of syntax. A study of syntactically ambiguous sentences showed that they can be successfully disambiguated by adjusting the rhythmic units to reflect syntactic structure. The hypothesis that isochrony is primarily perceptual was tested ...