Joanne L. Miller

Some effects of later-occurring information on the perception of stop consonant and semivowel

In three experiments, we determined how perception of the syllable-initial distinction between the stop consonant [b] and the semivowel [w], when cued by duration of formant transitions, is affected by parts of the sound pattern that occur later in time. For the first experiment, we constructed four series of syllables, similar in that each had initial formant transitions ranging from one short enough for [ba] to one long enough for [wa], hut different in overall syllable duration. The consequence in perception was that, as syllable duration increased, the [b-w] boundary moved toward transitions of longer duration. Then, in the second experiment, we increased the duration of the sound by adding a second syllable, [da], (thus creating [bada-wada]), and observed that lengthening the second syllable also shifted the perceived [b-w] boundary in the first syllable toward transitions of longer duration; however, this effect was small by comparison with that produced when the first syllable was lengthened equivalently. In the third experiment, we found that altering the structure of the syllable had an effect that is not to be accounted for by the concomitant change in syllable duration: lengthening the syllable by adding syllable-final transitions appropriate for the stop consonant [d] (thus creating [bad-wad]) caused the perceived [b-w] boundary to shift toward transitions of shorter duration, an effect precisely opposite to that produced when the syllable was lengthened to the same extent by adding steady-state vowel. We suggest that, in all these cases, the later-occurring information specifies rate of articulation and that the effect on the earlier-occurring cue reflects an appropriate perceptual normalization.

Phonetic prototypes: Influence of place of articulation and speaking rate on the internal structure of voicing categories

In this investigation, the effects of context on the perception of voicing contrasts specified by voice-onset-time (VOT) in syllable-initial stop consonants were examined. In an earlier paper [J.L. Miller and L.E. Volaitis, Percept. Psychophys. 46, 505-512 (1989)], it was reported that the listeners adjustment for one contextual variable, speaking rate, was not confined to the region of the phonetic category boundary, but extended throughout the phonetic category. The current investigation examines whether this type of perceptual remapping also occurs for another contextual variable, the place of articulation of the syllable-initial consonant. In a preliminary experiment that involved acoustic measurement of natural speech, it was confirmed that as place of articulation moves from labial to velar, VOT increases, and it was established that this occurs across a range of speaking rates (syllable durations). In the main experiments, which focused on the voiceless category, it was found that this acoustic change was reflected in perception not only as a shift in the location of the voiced-voiceless category boundary, but also a change in both the specific range of stimuli identified as members of the voiceless category and the set of stimuli judged to be the best exemplars, or prototypes, of the category. These findings extend earlier research by showing that a change in place of articulation, like a change in speaking rate, systematically alters the internal perceptual structure of voicing categories.

Articulation Rate and Its Variability in Spontaneous Speech: A Reanalysis and Some Implications

It is by now well established that during normal conversation talkers often produce large variation in the rate at which they speak. However, existing research suggests that this modification is largely due to changes in the amount of pausing during conversation, and much less to actual changes in articulation rate, that is, the rate at which the speech itself is produced. In an attempt to examine this issue further, we used a modified measurement procedure to reanalyze the speech data from 30 talkers in an interview situation. In contrast to the earlier analyses, we found that there was indeed substantial variation in articulation rate for these speakers, even within a single utterance of a single talker. The implications of these findings for theories of segmental perception and for models of speech planning are discussed.

Effect of speaking rate on the perceptual structure of a phonetic category

When listeners process temporal properties of speech that convey information about the phonetic segments of the language, they do so in a rate-dependent manner. This is seen as a shift in the location of the phonetic category boundary along a temporal continuum toward longer values of the acoustic property in question, as speech is slowed. In a series of experiments, we found that the adjustment for rate is not confined to the region of the category boundary, but extends throughout the phonetic category. Specifically, a change in rate modified the range of stimuli identified as members of a phonetic category, as well as which stimuli were overtly judged to be good exemplars of the category. These findings suggest that the listener’s adjustment for speaking rate entails a comprehensive perceptual remapping between acoustic signal and phonetic structure.

Speech, language, and communication

L. Frazier, Issues of Representation in Psycholinguistics. C.A. Fowler, Speech Production. L.C. Nygaard and D.B. Pisoni, Speech Perception: New Directions in Research and Theory. A. Cutler, Spoken Word Recognition and Production. M.S. Seidenberg, Visual Word Recognition: An Overview. K. Bock, Sentence Production: From Mind to Mouth. M.K. Tanenhaus and J.C. Trueswell, Sentence Comprehension. P.W. Jusczyk, Language Acquisition: Speech Sounds and the Beginnings of Phonology. E.V. Clark, Language Acquisition: The Lexicon and Syntax. S.E. Blumstein, The Neurobiology of Language. H.H. Clark and B. Bly, Pragmatics and Discourse. Subject Index.

Speaking Rate and Segments: A Look at the Relation between Speech Production and Speech Perception for the Voicing Contrast

When listeners process segmentally relevant properties of the speech signal they do so in a rate-dependent manner. This is seen as a shift in the perceptual category boundary; as rate declines and overall syllable duration increases, the category boundary moves toward a longer value of the acoustic property in question. Focusing on the /b/-/p/ distinction specified by voice onset time (VOT), we investigated whether the acoustic modifications that occur with an alteration in speaking rate accord with this pattern of perceptual boundary shift. Two main findings emerged. First, as speaking rate became slower and overall syllable duration became longer, the VOT value of the consonant, especially that of the voiceless /p/, also became longer. Second, and most important, the VOT value that optimally separated the /b/ and /p/ VOT distributions also changed with rate, increasing with increasing syllable duration. However, the magnitude of the boundary shift obtained for these production data was greater than that typically found in perceptual experiments. This suggests the existence of constraints on the extent to which the perceptual system can accommodate for alterations due to rate of speech.

Effects of speaking rate and lexical status on phonetic perception.

Among the contextual factors known to play a role in segmental perception are the rate at which the speech was produced and the lexical status of the item, that is, whether it is a meaningful word of the language. In a series of experiments on the word-initial /b/-/p/ voicing distinction, we investigated the conditions under which these factors operate during speech processing. The results indicated that under instructions of speeded responding, listeners could, on some trials, ignore some later occurring contextual information within the word that specified rate and lexical status. Importantly, however, they could not ignore speaking rate entirely. Although they could base their decision on only the early portion of the word, when doing so they treated the word as if it were physically short--that is to say, as if there were no later occurring information specifying a slower rate. This suggests that listeners always take account of rate when identifying the voicing value of a consonant, but precisely which information within the word is used to specify rate can vary with task demands.

Studies on the categorization of speech by infants

Abstract It is well-known that complexities exist in the mapping between the acoustic information in the speech signal and the phonetic categories of adult language users. We investigated whether the same complexities exist in the mapping between the speech signal and the forerunners of these categories in infants. For two classes of complexity, we found that the manner in which the categorization of information for speech occurs was virtually identical in infant and adult listeners. These findings indicate that the infant possesses finely tuned linguistically-relevant perceptual abilities, which undoubtedly facilitate and shape the task of language acquisition.

On the internal structure of phonetic categories: a progress report

There is growing evidence that phonetic categories have a rich internal structure, with category members varying systematically in category goodness. Our recent findings on this issue, which are summarized in this paper, underscore the existence and robustness of this structure and indicate further that the mapping between acoustic signal and internal category structure is complex: just as in the case of category boundaries, the best exemplars of a given category are highly dependent on acoustic-phonetic context and are specified by multiple properties of the speech signal. These findings suggest that the listeners representation of phonetic form preserves not only categorical information, but also fine-grained information about the detailed acoustic-phonetic characteristics of the language.

On the role of visual rate information in phonetic perception.

It is well established that listeners process segmentally relevant properties of the speech signal in relation to the rate at which the speech was produced. We investigated whether the critical rate information for this effect is limited to the auditory modality or, alternatively, whether visual rate information provided by the talker’s face also plays a role. Audio-visual syllables were created by pairing tokens from a moderate-rate, auditory /bi/-/pi/ series with visual tokens of /bi/ or /pi/ produced at a faster or slower rate of speech; these visual tokens provided information about speaking rate, but could not themselves be identified correctly as /bi/ or /pi/. Each audiovisual pairing produced the phenomenal experience of a single, unified syllable, /bi/ or /pi/, spoken at a single rate of speech. The change in visual rate information across the syllables influenced the judged rate of the audio-visual syllables and, more importantly, affected their identification as /bi/ or /pi/. These results indicate that visual information about speaking rate is relevant to the perception of voicing and, more generally, suggest that the mechanisms underlying rate-dependent speech processing have a bimodal (or amodal) component.