Variability in word duration as a function of probability, speech style, and prosody.

This article examines how probability (lexical frequency and previous mention), speech style, and prosody affect word duration, and how these factors interact. Participants read controlled materials in clear and plain speech styles. As expected, more probable words (higher frequencies and clear speech second mentions) were significantly shorter than less probable words, and lexical frequency words in plain speech were significantly shorter than those in clear speech. Interestingly, we found second mention reduction effects in both clear and second mention plain speech, indicating that while clear speech is hyper-articulated, this reduction hyper-articulation does not override probabilistic effects on duration. We also found an interaction between mention and frequency, but only in plain speech. High frequency words allowed more second mention reduction than low frequency words in plain speech, revealing a tendency to hypo-articulate as much as possible when all factors support it. Finally, we found that first mentions were more likely to be accented than second mentions. However, when these differences in accent likelihood were controlled, a significant second mention reduction effect remained. This supports the concept of a direct link between probability and duration, rather than a relationship solely mediated by prosodic prominence.