The effects of prosodic prominence and serial position on duration perception.

This study addresses how prosodic expectations affect perceptual discrimination. Prosodic expectations were created using natural recordings of six-syllable sentences in dactylic, iambic, and trochaic metrical patterns at two speech rates, slow and quick. PSOLA resynthesis was used to lengthen target syllables located in three different serial positions in each of the three patterns. Subjects made forced-choice comparisons of durational structure in an AX task. Lengthening was detected significantly better for strong syllables than for weak ones in all metrical patterns, serial positions, and at speech rates. The result obtains even when absolute duration is eliminated as a potential confound. Results are interpreted in the light of prior research showing that prosodically strong syllables offer perceptual advantages in recognition and identification tasks, even when prosodic strength is cued only by the prior context (and not by any acoustic phonetic properties of the target syllables). In conclusion, metrical expectations cause listeners to focus their attention on metrically prominent syllables, with attentional focus leading to better performance in tasks tapping multiple levels of processing.