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C A Fowler

Publications and source records attributed to C A Fowler.

At least 19 recordsLinked to original sources
PubMed1992

Fundamental frequency declination is not unique to human speech: evidence from nonhuman primates.

In human speech, declination of the fundamental frequency (F0) of the voice spans coherent units of an utterance and, therefore, signals where units begin and end. A rapid final fall at the end of an utterance provides a further indication of an utterance's ending. The occurrence of declination is sufficiently widespread across languages that several investigators have suggested it as a language universal. Language universals may be universal because they are part of a species-specific specialization for language or, alternatively, they may constitute conventionalizations of natural dispositions of the vocal tract that may serve a communicative function. Evidence is offered favoring the latter account for declination and the final fall by showing that vocal productions of vervet monkeys (Cercopithecus aethiops) and rhesus macaques (Macaca mulatta) show declination, and vervets show clear evidence of a final fall. Interestingly, the fall in F0 may serve some communicative role in the vocal exchanges of vervets and rhesus, analogous to its signalling function in human language.

Acoustics↗
PubMed1992

Declination of supralaryngeal gestures in spoken Italian.

Two experiments investigate a weakening of supralaryngeal gestures in an utterance, analogous in some ways to declination of fundamental frequency and amplitude. In one experiment, acoustic measures revealed progressive centralization of stressed /i/, /a/ and /u/ left to right in trisyllabic utterances read by Tuscan subjects. A second experiment, using speakers of a different (Northern) variety of Standard Italian, found reduction in jaw opening for stressed /a/ left to right, but generally failed to replicate a centralization of /i/. This experiment further suggested that the progressive weakening of supralaryngeal gestures is largely a phrase level rather than a word level phenomenon. Both experiments found a different, V-shaped, pattern of opening to be generally characteristic of unstressed syllables.

Adult↗
PubMed1992

Audiovisual integration in perception of real words.

Three experiments follow up on Easton and Basala's (1982) report that the "McGurk effect" (an influence of a visibly mouthed utterance on a dubbed acoustic one) does not occur when utterances are real words rather than nonsense syllables. In contrast, with real-word stimuli, Easton and Basala report a strong reverse effect whereby a dubbed soundtrack strongly affects identification of lipread words. In Experiment 1, we showed that a strong McGurk effect does obtain when dubbed real words are discrepant with observed words in consonantal place of articulation. A second experiment obtained only a weak reverse effect of dubbed words on judgments of lipread words. A final experiment was designed to provide a sensitive test of effects of lipread words on judgments of heard words and of heard words on judgments of lipread words. The findings reinforced those of the first two experiments that both effects occur, but, with place-of-articulation information discrepant across the modalities, the McGurk effect is strong and the reverse effect weak.

Attention↗
PubMed1991

Listening with eye and hand: cross-modal contributions to speech perception.

Three experiments investigated the "McGurk effect" whereby optically specified syllables experienced synchronously with acoustically specified syllables integrate in perception to determine a listener's auditory perceptual experience. Experiments contrasted the cross-modal effect of orthographic on acoustic syllables presumed to be associated in experience and memory with that of haptically experienced and acoustic syllables presumed not to be associated. The latter pairing gave rise to cross-modal influences when Ss were informed that cross-modal syllables were paired independently. Mouthed syllables affected reports of simultaneously heard syllables (and vice versa). These effects were absent when syllables were simultaneously seen (spelled) and heard. The McGurk effect does not arise from association in memory but from conjoint near specification of the same causal source in the environment--in speech, the moving vocal tract producing phonetic gestures.

Adult↗
PubMed1991

Audiovisual investigation of the loudness-effort effect for speech and nonspeech events.

There is some evidence that loudness judgments of speech are more closely related to the degree of vocal effort induced in speech production than to the speech signal's surface-acoustic properties such as intensity. Other researchers have claimed that speech loudness can be rationalized simply by considering the acoustic complexity of the signal. Because vocal effort can be specified optically as well as acoustically, a study to test the effort-loudness hypothesis was conducted that used conflicting audiovisual presentations of a speaker that produced consonant-vowel syllables with different efforts. It was predicted that if loudness judgments are constrained by effort perception rather than by simple acoustic parameters, then judgments ought to be affected by visual as well as auditory information. It is shown that loudness judgments are affected significantly by visual information even when subjects are instructed to base their judgments only on what they hear. A similar (though less pronounced) patterning of results is shown for a nonspeech "clapping" event, which attests to the generality of the loudness-effort effect previously thought to be special to speech. Results are discussed in terms of auditory, fuzzy logical, motor, and ecological theories of speech perception.

Adult↗
PubMed1991

Auditory perception is not special: we see the world, we feel the world, we hear the world.

The literature on "contrast" provides no evidence that durational contrast should occur in the speech and nonsence signals used in research cited by Diehl et al. [J. Acoust. Soc. Am. 89, 2905-2909 (1991)]. Moreover, there is evidence that, in comparable signals, it does not occur. Accordingly, their own account of the collection of findings on rate normalization is not viable. Their comments on my research do not imperil my interpretation of it or challenge my criticism that classification judgments of acoustically analogous speech and nonsense signals do not permit interpretation, by themselves, in terms of underlying auditory-system mechanisms. Their arguments that in auditory perception, uniquely, we hear proximal stimulation, not its physical causal sources, is implausible. Their theoretical perspective generally, I argue, is unrealistic.

Auditory Perception↗
PubMed1990

Duplex perception: a comparison of monosyllables and slamming doors.

Duplex perception has been interpreted as revealing distinct systems for general auditory perception and speech perception. The systems yield distinct experiences of the same acoustic signal, the one conforming to the acoustic structure itself and the other to its source in vocal-tract activity. However, this interpretation has not been tested by examining whether duplex perception can be obtained for nonspeech sounds that are not plausibly perceived by a specialized system. In five experiments, we replicate some of the phenomena associated with duplex perception of speech using the sound of a slamming door. Similarities between subjects' responses to syllables and door sounds are striking enough to suggest that some conclusions in the speech literature should be tempered that (a) duplex perception is special to sounds for which there are perceptual modules and (b) duplex perception occurs because distinct systems have rendered different percepts of the same acoustic signal.

Adult↗
PubMed1990

Sound-producing sources as objects of perception: rate normalization and nonspeech perception.

In a variety of experiments and paradigms, researchers have attempted to determine whether or not speech perception is specialized by comparing perception of speech syllables to perception of nonspeech analogs. While nonspeech analogs appear optimal as comparisons to speech because they are acoustically similar without being recognized as speechlike, it is argued that the comparison they offer is confounded and uninterpretable. Two experiments are designed to show that, in auditory perception generally where acoustic signals are causal consequences of mechanical events, perceptual experiences are of the mechanical events themselves, not of the acoustic signal. This has two consequences. One is that there is a confounding in comparisons of speech with sine wave analogs that, whereas the one perceived as speech also has a definite causal source, the other, perceived as nonspeech, has an indeterminate or ambiguous source. A second is that response patterns in classification tasks such as those used in the literature comparing speech to nonspeech will reflect properties of the perceived sound-producing event; they will not provide a clear window on auditory system processes used to recover event properties. Experiment 3 is designed to show that perception of many acoustic-signal-producing events can appear to be special by the logic of speech-sine wave comparisons--even events that cannot plausibly be supposed to involve a specialization.

Adult↗
PubMed1990

Young infants' perception of liquid coarticulatory influences on following stop consonants.

Phonetic segments are coarticulated in speech. Accordingly, the articulatory and acoustic properties of the speech signal during the time frame traditionally identified with a given phoneme are highly context-sensitive. For example, due to carryover coarticulation, the front tongue-tip position for /1/ results in more fronted tongue-body contact for a /g/ preceded by /1/ than for a /g/ preceded by /r/. Perception by mature listeners shows a complementary sensitivity--when a synthetic /da/-/ga/ continuum is preceded by either /al/ or /ar/, adults hear more /g/s following /l/ rather than /r/. That is, some of the fronting information in the temporal domain of the stop is perceptually attributed to /l/ (Mann, 1980). We replicated this finding and extended it to a signal-detection test of discrimination with adults, using triads of disyllables. Three equidistant items from a /da/-/ga/ continuum were used preceded by /al/ and /ar/. In the identification test, adults had identified item ga5 as "ga,' and dal as "da,' following both /al/ and /ar/, whereas they identified the crucial item d/ga3 predominantly as "ga' after /al/ but as "da' after /ar/. In the discrimination test, they discriminated d/ga3 from da1 preceded by /al/ but not /ar/; compatibly, they discriminated d/ga3 readily from ga5 preceded by /ar/ but poorly preceded by /al/. We obtained similar results with 4-month-old infants. Following habituation to either ald/ga3 or ard/ga3, infants heard either the corresponding ga5 or da1 disyllable. As predicted, the infants discriminated d/ga3 from da1 following /al/ but not /ar/; conversely, they discriminated d/ga3 from ga5 following /ar/ but not /al/. The results suggest that prelinguistic infants disentangle consonant-consonant coarticulatory influences in speech in an adult-like fashion.

Adult↗
PubMed1989

Duplex perception: some initial findings concerning its neural basis.

Duplex perception is the simultaneous perception of a speech syllable and of a nonspeech "chirp," and occurs when a single formant transition and the remainder (the "base") of a synthetic syllable are presented to different ears. The current study found a slight but nonsignificant advantage for correct labeling of the fused syllable when the chirp was presented to the left ear. This advantage was amplified in the performance of a "split-brain" subject. A subject with a left pontine lesion performed at chance level when the chirp was presented to her left ear. These findings suggest that some, if not complete, ipsilateral suppression does occur in the dichotic fusion procedure, and that identification of the fused syllable is maximal when the left hemisphere fully processes the linguistic characteristics of the base (through contralateral presentation), and at least minimally processes the frequency transition information of the chirp (through ipsilateral presentation).

Adult↗
PubMed1989

P-center judgments are generally insensitive to the instructions given.

The perceptual moment of occurrence of a syllable, its P-center, has frequently been examined by instructing subjects to adjust a series of speech sounds until they sounded isochronous. The present two experiments examined the effect of changing the instructions. In addition to the overall isochrony instructions, we asked subjects to align pairs of syllables so that the syllable onsets, vowel onsets, or syllable offsets sounded isochronous. In the first experiment, 3 of 4 subjects showed no difference among the first three instruction sets, and the changes introduced by the fourth went in the wrong direction. All subjects found it impossible to make alignments with respect to offsets. In the second experiment, vowel durations of two versions of some stimuli differed by 100 ms, to enhance the difference in syllable rhyme durations. Two subjects received the same instruction sets as in Experiment 1, and again found alignment with respect to offsets impossible. These subjects showed differences among the other instruction sets, although the direction and magnitude of the differences indicated that they had not succeeded in changing their timing criteria. The results indicate that P-center alignments are the syllable timing judgments that subjects most naturally make, and they may, indeed, be the only isochrony judgments that subjects can make reliably.

Analysis of Variance↗
PubMed1988

Coarticulatory influences on the perceived height of nasal vowels.

Certain of the complex spectral effects of vowel nasalization bear a resemblance to the effects of modifying the tongue or jaw position with which the vowel is produced. Perceptual evidence suggests that listener misperceptions of nasal vowel height arise as a result of this resemblance. Whereas previous studies examined isolated nasal vowels, this research focused on the role of phonetic context in shaping listeners' judgments of nasal vowel height. Identification data obtained from native American English speakers indicated that nasal coupling does not necessarily lead to listener misperceptions of vowel quality when the vowel's nasality is coarticulatory in nature. The perceived height of contextually nasalized vowels (in a [bVnd] environment) did not differ from that of oral vowels (in a [bVd] environment) produced with the same tongue-jaw configuration. In contrast, corresponding noncontextually nasalized vowels (in a [bVd] environment) were perceived as lower in quality than vowels in the other two conditions. Presumably the listeners' lack of experience with distinctive vowel nasalization prompted them to resolve the spectral effects of noncontextual nasalization in terms of tongue or jaw height, rather than velic height. The implications of these findings with respect to sound changes affecting nasal vowel height are also discussed.

Humans↗
PubMed1987

Formal relationships among words and the organization of the mental lexicon.

A series of experiments investigated the role of orthography in the organization of the mental lexicon. A pilot experiment had found no effect of formal overlap between words on a repetition priming task at a lag of 56 intervening items. The first two experiments reported here used a lag of zero and varied SOA. Formal priming was found at SOAs of 1,650 milliseconds and less. However, reducing the proportion of related primes and targets in the experiment reduced formal priming. Moreover, it did so not by affecting response times to formally related primes and targets but by reducing response times to comparison trials in which primes and targets were unrelated. This led to a hypothesis that the formal priming we had observed was only apparent and due to strategic inhibition of responses to unrelated prime-target pairs. The final experiment reduced the proportion of responses to related targets further and examined formal priming at lags of 0, 1, 3, and 10. No formal priming was found under these conditions. Across all experiments, where formal priming occurred, it was due to changes in levels of inhibitory priming in comparison conditions. The conclusion is drawn that convincing evidence for an orthographic or phonological organization of the lexicon is not obtainable using priming procedures.

Cues↗
PubMed1987

A new burn area assessment chart.

A series of body charts have been designed that are more representative of changing body proportion with increasing age. Being easier to use, these charts have led to a better estimate by the casualty doctor of the body surface area that has been burned.

Adolescent↗
PubMed1987

Domain-final lengthening and foot-level shortening in spoken English.

The literature describes two kinds of durational influence on the syllables of an utterance. They are a lengthening of syllables before many syntactic boundaries ('domain-final lengthening') and a shortening of stressed syllables followed by unstressed syllables ('foot-level shortening'). In the present study we examined the relationship between these two timing phenomena. In particular, we examined the possibility that syntactic boundaries at which lengthening occurs delimit the domains over which foot-level shortening is realized. To test this hypothesis, we varied the syllabic structure of metrical feet spanning word boundaries that either coincided with a noun-phrase (NP)/verb-phrase (VP) boundary or did not. Comparison of stressed syllable durations in these conditions failed to confirm the hypothesis. Instead, unstressed syllables shortened stressed syllables by the same duration across an NP/VP boundary as within a phrase. Our findings suggest that the two effects are independent. The finding that foot-level shortening spans finally-lengthened syntactic boundaries is discussed in relation to theories of the shortening effect.

Humans↗