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Biomedical subjects

C A Fowler

Publications and source records attributed to C A Fowler.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1987

Resuscitation fluid composition and myocardial performance during burn shock.

The present study examines the effects of resuscitation fluid composition on myocardial function, myocardial high-energy phosphate content, and survival following third-degree anesthetic burn to 35-40% body surface area in the guinea pig. Treatment regimens used were 1) no resuscitation, 2) isotonic saline, 3) Ringer's lactate and 4) Ringer's acetate. Fluids were administered at the rate of 0.334 ml/kg/hr/% burn for 4 hr following injury, at which time myocardial function was assessed. Nonburned animals served as controls. In isolated working hearts, significant depression of myocardial function was observed in nonresuscitated and saline-resuscitated animals as evidenced by decreased cardiac output, dP/dt, -dP/dt, and stroke work. Lactate resuscitation produced some improvement in these parameters but did not restore them to those of nonburned control animals. In contrast, Ringer's acetate resuscitation resulted in normal cardiac output and contractility. Myocardial ATP content of hearts obtained from the various resuscitation groups did not differ from that of nonburned control hearts, except for hearts from Ringer's lactate group, which were significantly lower in myocardial ATP than those of the other groups. No differences were found in creatine phosphate content. Resuscitation with the different fluid regimens for 48 hr produced significant differences in survival. Fluids were given at the rate of 4 ml/kg/% burn for 24 hr. Half of the fluid was given in the first 8 hr and the rest during the remaining 16 hr. Nonresuscitated and saline-resuscitated animals showed significant mortality by 24 hr, whereas lactate- and acetate-treated animals had survival rates of 100% and 87.5%, respectively. However, by 48 hr, only acetate-treated animals survived. These data indicate that important differences exist in the effectiveness of different resuscitation fluids and that Ringer's lactate, the fluid most often utilized clinically, may not provide optimum benefit. In light of these results, serious consideration should be given to the substitution of acetate for lactate during the resuscitation of burn shock patients.

Animals↗
PubMed1986

Perception of syllable timing by prebabbling infants.

Adults hear alternating syllables with isochronous syllable onset-onset times as having a long-short, alternating rhythm when the syllables differ in initial consonant. This occurs because adults attend to syllable-internal events, called the "P centers" or "stress beats", rather than to syllable onsets. Thus they report that stress-beat aligned speech is isochronous and stress-beat aligned clicks are synchronized with the speech. The question asked here is whether, like adults, infants attend to the timing of syllable stress beats. In experiment 1, infants showed differences in time to habituate to sequences of alternating monosyllables, [bad] and [strad], having two different onset-onset times (onset- and stress-beat-timed) and two different placements of clicks on the syllables (on syllable onsets and on stress beats). Infants habituated more slowly to sequences with clicks on the stress beats than to sequences with clicks on syllable onsets and most slowly of all to stress-beat-timed speech with clicks on the stress beats. To interpret these findings, a second experiment was run using sequences only of the syllable [strad] so that speech timing measured according to onsets and stress beats was the same. Syllables had isochronous timing or a long-short alternating rhythm, corresponding to two possible ways of hearing the stress-beat-timed speech of experiment 1. In addition, two patterns of click placement were compared, uniform and syncopated, corresponding to two ways of hearing the stress-beat aligned clicks of experiment 1. The patterns of sucking times in the two experiments match exactly if stress-beat aligned speech in experiment 1 is identified with the isochronous speech of experiment 2 and the stress-beat aligned clicks of experiment 1 match with the uniformly timed clicks of experiment 2. It is inferred from this correspondence that infants perceive stress beats and stress-beat timing of syllables as adults do.

Attention↗
PubMed1984

Functionally specific articulatory cooperation following jaw perturbations during speech: evidence for coordinative structures.

In three experiments we show that articulatory patterns in response to jaw perturbations are specific to the utterance produced. In Experiments 1 and 2, an unexpected constant force load (5.88 N) applied during upward jaw motion for final /b/ closure in the utterance /baeb/ revealed nearly immediate compensation in upper and lower lips, but not the tongue, on the first perturbation trial. The same perturbation applied during the utterance /baez/ evoked rapid and increased tongue-muscle activity for /z/ frication, but no active lip compensation. Although jaw perturbation represented a threat to both utterances, no perceptible distortion of speech occurred. In Experiment 3, the phase of the jaw perturbation was varied during the production of bilabial consonants. Remote reactions in the upper lip were observed only when the jaw was perturbed during the closing phase of motion. These findings provide evidence for flexibly assembled coordinative structures in speech production.

Adult↗