Preceding vocalic information can cue final consonant voicing for native English speakers. This study examines subjects' use of two vocalic cues, vocalic duration, and F1 offset frequency, as a function of two native language factors, experience with final stop consonants, and experience with phonemic vowel length. Native speakers of English are compared to native speakers of Japanese and Mandarin Chinese who are learning English as a second language. Experiment 1 measured the F1 offset frequency and vocalic duration in productions of "pod" and "pot." Experiment 2 assessed identification of natural tokens of "pod" and "pot" with and without closure segments and bursts. Experiment 3 assessed categorization of synthetic "pod"-"pot" stimuli that systematically manipulated vocalic duration and F1 offset frequency. Native speakers of English showed the strongest implementation of and sensitivity to vocalic duration, Mandarin speakers showed significantly weaker effects, and Japanese speakers fell in between. Group-related differences in use of F1 offset frequency were smaller, and much clearer in the case of production than perception. It is hypothesized that a lack of experience with final consonants penalizes use of vocalic cues among the Japanese and Mandarin subjects, in general. The advantage of the Japanese subjects for use of vocalic duration further suggests a facilitation effect of experience with phonemic vowel length.

The fuzzy logic model of perception (FLMP) is analyzed from a measurement-theoretic perspective. FLMP has an impressive history of fitting factorial data, suggesting that its probabilistic form is valid. The authors raise questions about the underlying processing assumptions of FLMP. Although FLMP parameters are interpreted as fuzzy logic truth values, the authors demonstrate that for several factorial designs widely used in choice experiments, most desirable fuzzy truth value properties fail to hold under permissible rescalings, suggesting that the fuzzy logic interpretation may be unwarranted. The authors show that FLMP's choice rule is equivalent to a version of G. Rasch's (1960) item response theory model, and the nature of FLMP measurement scales is transparent when stated in this form. Statistical inference theory exists for the Rasch model and its equivalent forms. In fact, FLMP can be reparameterized as a simple 2-category logit model, thereby facilitating interpretation of its measurement scales and allowing access to commercially available software for performing statistical inference.

We examined whether children modify their perceptual weighting strategies for speech on the basis of the order of segments within a syllable, as adults do. To this end, fricative-vowel (FV) and vowel-fricative (VF) syllables were constructed with synthetic noises from an If I-to-/s I continuum combined with natural lal and lui portions with transitions appropriate for a preceding or a following IfI or Is/. Stimuli were played in their original order to adults and children (ages of 7 and 5 years) in Experiment 1 and in reversed order in Experiment 2.The results for adults and, to a lesser extent, those for 7-year-olds replicated earlier results showing that adults assign different perceptual weights to acoustic properties, depending on segmental order. In contrast, results for 5-year-oldssuggested that these listeners applied the same strategies during fricative labeling, regardless of segmental order. Thus, the flexibility to modifyperceptual weighting strategies for speech according to segmental order apparently emerges with experience.

Studies comparing children's and adults' labeling of speech stimuli have repeatedly shown that children's phonological decisions are more strongly related to portions of the signal that involve rapid spectral change (i.e., formant transitions) and less related to other signal components than are adults' decisions. Such findings have led to a model termed the Developmental Weighting Shift, which suggests that children initially assign particularly strong weight to formant transitions to help delimit individual words in the continuous speech stream but gradually modify these strategies to be more like those of adults as they learn about word-internal structure. The goal of the current study was to test a reasonable alternative: that these apparent age-related differences in perceptual weighting strategies for speech are instead due to age-related differences in auditory sensitivity. To this end, difference limens (DLs) were obtained from children (ages 5 and 7 years) and adults for three types of acoustic properties: dynamic-spectral, static-spectral, and temporal. Two testable hypotheses were offered: Labeling results could reflect either absolute differences in sensitivity between children and adults or relative differences in sensitivity within each group. Empirical support for either hypothesis would indicate that apparent developmental changes in perceptual weighting strategies are actually due to developmental changes in auditory sensitivity to acoustic properties. Results of this study contradicted predictions of both hypotheses, sustaining the suggestion that children's perceptual weighting strategies for speech-relevant acoustic properties change as they gain experience with a native language.

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 ...