Court S. Crowther

Use of vocalic cues to consonant voicing and native language background: The influence of experimental design

For native speakers of English and several other languages, preceding vocalic duration andFi offset frequency are two of the cues that convey the stop consonant voicing distinction in wordfinal position. For speakers learning English as a second language, there are indications that use of vocalic duration, but notFl offset frequency, may be hindered by a lack of experience with phonemic (i.e., lexical) vowel length (the “phonemic vowel length account”: Crowther & Mann, 1992). In this study, native speakers of Arabic, a language that includes a phonemic vowel length distinction, were tested for their use of vocalic duration andF1 offset in production and perception of the English consonant-vowel-consonant forms pod and pot. The phonemic vowel length hypothesis predicts that Arabic speakers should use vocalic duration extensively in production and perception. On the contrary, experiment l repealed that, consistent with Flege and Port’s (1981) findings, they produced only slightly (but significantly) longer vocalic segments in their pod tokens. It further indicated that their productions showed a significant variation inFl offset as a function of final stop voicing. Perceptual sensitivity to vocalic duration andFl offset as voicing cues was tested in two experiments. In experiment 2, we employed a factorial combination of these two cues and a finely spaced vocalic duration continuum. Arabic speakers did not appear to be very sensitive to vocalic duration, but they were abort as sensitive as native English speakers toF1 offset frequency. In Experiment 3, we employed a one-dimensional continuum of more widely spaced stimuli that varied only vocalic duration. Arabic speakers showed native-English-like sensitivity to vocalic duration- Anexplanation based on tie perceptual anchor theory of context coding (Braida et al., 1984; Macmillan, 1987; Macmillan, Braida, & Goldberg, 1987) and phoneme perception theory (Schouten & Van Hessen, 2992) is offered to reconcile the apparently contradictory perceptual findings. The explanation does not attribute native-English-like voicing perception to the Ambit subjects. The findings in this study call fox a modification of the phonemic vowel length hypothesis.

Children’s perceptual weighting strategies for speech are not as flexible as adults

Mann and Soli (1991) showed that adults modify their perceptual weighting strategies for the same phonetic decision based on the order of segments within syllables. The authors exmained whether children similarly modify their perceptual weighting strategies. Fricative‐vowel (FV) and vowel‐fricative (VF) syllables were constructed with synthetic fricative nosies varying from /∫/ to /s/, and natural /ɑ/ and /u/ portions with transitions appropriate for a preceding or a following /∫/ or /s/. Spectrograms revealed that the acoustic information about fricative identity provided by the vocalic portion was impoverished for VF compared to FV syllables. These stimuli were played in their original order to adults and children (ages 7 and 5) in experiment 1, and in reverse order in experiment 2. Results for adults and, to a lesser extent, for 7‐year‐olds replicated earlier results showing that the perceptual weights assigned to acoustic properties within the vocalic portion differ depending on segmental order. In co...

Integration of acoustic information in the perception of [s] ± stop clusters by children and adults

To compare the integration of acoustic information in phonetic perception by young children and adults, second formant frequency at voicing onset (F2 onset) and gap duration were varied as cues distinguishing ‘‘spa’’ and ‘‘sa.’’ Listeners performed same–different (AX) discrimination in four conditions. The gap of the standard (A) stimulus was always consistent with ‘‘spa;’’ gaps of the comparison (X) stimuli decreased in duration along a continuum, thus becoming more consistent with ‘‘sa.’’ In the two ‘‘one‐cue’’ conditions, F2 onset was the same for the A and X stimuli. In the ‘‘two‐cue cooperating’’ condition, F2 onset for stimulus A supported ‘‘spa,’’ and F2 onset for X stimuli supported ‘‘sa.’’ In the ‘‘two‐cue conflicting’’ condition, F2 onset for stimulus A supported ‘‘sa,’’ and F2 onset for X stimuli supported ‘‘spa.’’ Results led to three conclusions: (1) Child and adult discrimination performance was similar overall, suggesting that the child‐adult differences across conditions were not due to di...

Modeling processing dependences in speech perception.

The goal of this work was to determine whether acoustic cues to the phonetic features of a segment are processed independently. For stop–vowel (CV) syllables, one point of controversy concerns whether place information (as conveyed by formant transitions) and voicing information (as conveyed by VOT) are processed mutually independently. In this experiment, a replication of Massaro and Oden [J. Acoust. Soc. Am. 67, 996–1013 (1980)], F2 and F3 transitions and VOT were manipulated as place and voicing cues in CVs. Members of a family of multinomial models, including FLMP, were fitted to each subject’s data. FLMP, which assumes that processing is independent at both the perceptual and decisional levels, failed to account for the data. Two other models retained the perceptual independence assumption, but one assumed the voicing decision was contingent on the outcome of the place decision, and the other assumed the opposite contingency. Both fitted better than FLMP, but nevertheless were rejected on statistical...

Re‐examining age‐related differences in the perception of ‘‘say/stay.’’

Previous ‘‘say/stay’’ perception studies using synthetic stimuli posited F1‐onset frequency and gap duration as the relevant cues. Children needed shorter gaps than adults to respond ‘‘stay’’ when F1 onset weakly indicated ‘‘stay,’’ suggesting that children weight that formant transition more. Replicating these experiments with natural speech produced unexpected findings. Acoustic analysis of natural ‘‘say’’ and ‘‘stay’’ tokens showed that: (1) F1 onset did not vary for ‘‘say’’ and ‘‘stay;’’ (2) F2/F3 onsets did vary; and (3) a burst was present in ‘‘stay.’’ Perceptual stimuli, therefore, consisted of natural, burstless vocalic portions from ‘‘say’’ and ‘‘stay,’’ and these same portions with a burst added. Each portion was combined with a natural ‘‘s’’ noise at seven gap durations. The burst effect was stronger for adults than children, and F2/F3 onset had an effect only for burstless stimuli. A second experiment was designed to examine the effects of F2/F3 in burstless stimuli, but adults failed to hear ...

Multinomial models of speech perception

It is often the case that two different acoustic cues can influence perception of both of two adjacent phonemes within a syllable. In such cases, it is of interest to determine whether the cues are evaluated independently; that is, does a listener’s evaluation of one cue influence evaluation of the other cue? Another, related question is whether, as some researchers claim, phoneme decisions are dependent in the sense that, when cued by the same information, the decisions compete for the information. This study modeled data from a two factor, four category experiment in which F1 offset frequency and vowel duration cue both voicing and vowel identity in CVC syllables. A family of multinomial processing tree models [e.g., D. M. Riefer and W. H. Batchelder, Psychol. Rev. 95, 318–339 (1988)], of which the fuzzy logic model of perception for the two factor, four category design is a special case, was developed and tested to explore the independence issues. This modeling approach is highly flexible and allows on...

Inferring degree of coarticulation and relational invariance of stop place in CV’s using locus equations

Locus equations relating target and onset frequency of F2 (F2t and F2o, respectively) have been successful in distinguishing stop consonant place of articulation independent of vowel context [e.g., Sussman et al., J. Acoust. Soc. Am. 90, 1309–1325 (1991)]. These linear equations are of the form F2o=a(F2t)+c. The slope parameter a is generally interpreted as indicating not only place of articulation, but extent of coarticulation [e.g., D. Krull, PERILUS V, 43–61 (1987)] as well. The intercept parameter c often is not interpreted explicitly, except in cases where the slope is found to be near zero. The locus equation technique is considered from several different viewpoints. Locus equations are analyzed empirically by examining changes that occur in estimated slope and intercept when a trained phonetician simulates different degrees of C‐V coarticulation. Differences in extent of coarticulation are also measured using electropalatography, and these measurements are compared with slope and intercept paramete...

Use of vocalic cues to final consonant voicing in perception and production of English CVC’s by native speakers of Arabic.

Native Arabic speakers who were either late learners (first resided in an English speaking country after high school) or early learners (first resided during high school) were compared in two experiments that tested their use of vocalic duration and F1 offset frequency as final consonant voicing cues in the English CVC’s ‘‘pod’’ and ‘‘pot.’’ Experiment 1 measured both vocalic duration and F1 offset frequency of subjects’ productions of these syllables; and experiment 2 considered their perception of tokens from synthetic ‘‘pod’’–‘‘pot’’ continua that varied vocalic duration and F1 offset. The results indicate some effects of native language experience and age of learning. Use of vocalic duration in production was greater for early than late learners, although considerably smaller than that of native English speakers. The early learners showed native‐like sensitivity to vocalic duration as a voicing cue, but the late learners did not. The range of F1 offset frequency differences tended to be smaller than i...