The relative weighting of acoustic properties in the perception of [s]+stop clusters by children and adults

Abstract

Weexamined the perceptual weighting by children and adults of the acoustic properties specifying complete closure of the vocal tract following a syllable-initial [s], Experiment 1 was a novel manipulation of previously examined acoustic properties (duration of a silent gap and first formant transition) and showed that children weight the first formant transition more than adults. Experiment 2, an acoustic analysis of naturally produced say and stay, revealed that, contrary to expectations, a burst can be present in stay and that first formant transitions do not necessarily distinguish say and stay in natural tokens. Experiment 3 manipulated natural speech portions to create stimuli that varied primarily in the duration of the silent gap and in the presence or absence of a stop burst, and showed that children weight these stop bursts less than adults. Taken together, the perception experiments support claims that children integrate multiple acoustic properties as adults do, but that they weight dynamic properties of the signal more than adults and weight static properties less.Phonetic perception requires the integration of multiple acoustic properties from across the spectral and temporal domains. Consequently, a change in the setting of one property alters the settings of other properties needed to elicit a specific phonetic decision. These reciprocal relations among acoustic properties, known as "trading relations," have been demonstrated by numerous labeling experiments (e.g., Bailey & Summerfield, 1980;Best, Morrongiello, & Robson, 1981; Dorman, StuddertKennedy, & Raphael, 1977;Fitch, Halwes, Erickson, & Liberman, 1980;Mann & Repp, 1980;Repp, 1982;Repp, Liberman, Eccardt, & Pesetsky, 1978;Summerfield & Haggard, 1977). Strictly speaking, demonstrating that a trading relation holds between acoustic properties for a phonetic category does not imply "perceptual equivalence" among (or between) those acoustic properties.' That is, stimuli that have different combinations of parameter settings across properties could elicit the same category response from listeners while remaining perceptually discriminable, especially given that typical labeling experiments employ only two category labels.However, several experiments have demonstrated perceptual equivalence among acoustic properties known to trade. Both Fitch et al. (1980) and Best et al. (1981) showed that longer durations of silence between an [s] noise and a vocalic portion were needed for adults to assign [s] +stop This work was supported by Research Grant 5 R01 DC 00633 to S.N. We thank Nancy Luke and John Schneider for help running subjects and Catherine Best, Joanne Miller, Donna Neff, Michael StuddertKennedy, and two anonymous reviewers for helpful comments on an earlier draft of this paper. Correspondence should be addressed to S. Nittrouer, Boys Town National Research Hospital, 555 North 30th St., Omaha, NE 68131 (e-mail: nittrouer@boystown.org). 51labels to stimuli when formant frequencies at voicing onset were high rather than low. That is, these two ...

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