Individual talkers differ in the acoustic properties of their speech, and at least some of these differences are in acoustic properties relevant for phonetic perception. Recent findings from studies of speech perception have shown that listeners can exploit such differences to facilitate both the recognition of talkers' voices and the recognition of words spoken by familiar talkers. These findings motivate the current study, whose aim is to examine individual talker variation in a particular phonetically-relevant acoustic property, voice-onset-time (VOT). VOT is a temporal property that robustly specifies voicing in stop consonants. From the broad literature involving VOT, it appears that individual talkers differ from one another in their VOT productions. The current study confirmed this finding for eight talkers producing monosyllabic words beginning with voiceless stop consonants. Moreover, when differences in VOT due to variability in speaking rate across the talkers were factored out using hierarchical linear modeling, individual talkers still differed from one another in VOT, though these differences were attenuated. These findings provide evidence that VOT varies systematically from talker to talker and may therefore be one phonetically-relevant acoustic property underlying listeners' capacity to benefit from talker-specific experience.

There is converging evidence that aging causes a progressive decline in the central processing of speech and that this decline is greater for left-ear than for right-ear input. In the present paper we investigated, by means of a dichotic sentence identification paradigm, some parameters of the 'leftear effect." We analyzed the clinical records of 366 individuals, 203 males and 163 females, to whom the Dichotic Sentence Identification (DSI) Test had been administered as part of routine audiometric assessment. Subjects ranged in age from B to 91 yr.The DSI test was always carried out in two modes: free report (FR) and directed report (DR). In the FR mode the subject reported what was heard in both ears. In the DR mode the subject reported only what was heard in one precued ear. In half of the trials the right ear was precued, in the other half the left ear was precued. Findings confirm a progressively larger righkar advantage, or left-ear deficit, with increasing age. We'document this effect in both the FR and DR modes, then demonstrate that the effects cannot be attributed to interaural asymmetries in threshold sensitivity. Comparison of male and female data suggest a gender difference in the effect of age on the left-ear deficit. Males show a larger effect then females in both modes of test administration. Finally, we propose a model of dichotic listening performance that attempts to explain ear asymmetry as the linear combination of an auditory/structural component and a task-relatedhognitive component. We then show how these hypothetical components change with age in the present sample. (Ear BE Hearing 1994;15;274-286)It has long been recognized that the right ear enjoys an advantage over the left ear in the processing of dichotic speech and speech-like signals [For recent comprehensive reviews see Hugdahl (1988) and Hellige (199311. This right-ear advantage (REX) in dichotic listening is customarily explained by the hypothesis that the right ear enjoys privileged access to the left hemisphere, the hemisphere dominant for the processing of speech (e.g., Zaidel, 1983).There is conflicting evidence on whether the REA changes with age. Borod and Goodglass (19801, Gelfand, Hoffman, Waltzman, and Viper (19801, and Martini et al. (1988) found no age effect on the REA. On the other hand, Horning (19721, Clark and Knowles (1973), and Johnson et al. (1979) all reported an increase in the REA in elderly subjects.More recently Jerger, Stach, Johnson, Loiselle, and Jerger (1990) studied the effect of increasing age on performance in a dichotic sentence-identification paradigm. They found that age-related decrease in performance was greater for the left ear than for the right ear. Finally, Jerger and Jordan (1992) compared young and elderly listeners on a dichotic, sound-field, cued-listening task. The REA was substantially larger in the elderly group than in the young adults. Interestingly, there have also been reports of an REA in monaural tasks involving difficult listening. Investigators have demonstrated greater declin...

Recent findings in the domains of word and talker recognition reveal that listeners use previous experience with an individual talker's voice to facilitate subsequent perceptual processing of that talker's speech. These findings raise the possibility that listeners are sensitive to talker-specific acoustic-phonetic properties. The present study tested this possibility directly by examining listeners' sensitivity to talker differences in the voice-onset-time (VOT) associated with a word-initial voiceless stop consonant. Listeners were trained on the speech of two talkers. Speech synthesis was used to manipulate the VOTs of these talkers so that one had short VOTs and the other had long VOTs (counterbalanced across listeners). The results of two experiments using a paired-comparison task revealed that, when presented with a short- versus long-VOT variant of a given talker's speech, listeners could select the variant consistent with their experience of that talker's speech during training. This was true when listeners were tested on the same word heard during training and when they were tested on a different word spoken by the same talker, indicating that listeners generalized talker-specific VOT information to a novel word. Such sensitivity to talker-specific acoustic-phonetic properties may subserve at least in part listeners' capacity to benefit from talker-specific experience.

Two speech production experiments tested the validity of the traditional method of creating voice-onset-time (VOT) continua for perceptual studies in which the systematic increase in VOT across the continuum is accompanied by a concomitant decrease in the duration of the following vowel. In experiment 1, segmental durations were measured for matched monosyllabic words beginning with either a voiced stop (e.g., big, duck, gap) or a voiceless stop (e.g., pig, tuck, cap). Results from four talkers showed that the change from voiced to voiceless stop produced not only an increase in VOT, but also a decrease in vowel duration. However, the decrease in vowel duration was consistently less than the increase in VOT. In experiment 2, results from four new talkers replicated these findings at two rates of speech, as well as highlighted the contrasting temporal effects on vowel duration of an increase in VOT due to a change in syllable-initial voicing versus a change in speaking rate. It was concluded that the traditional method of creating VOT continua for perceptual experiments, although not perfect, approximates natural speech by capturing the basic trade-off between VOT and vowel duration in syllable-initial voiced versus voiceless stop consonants.

Previous research has shown that phonetic categories have a graded internal structure that is highly dependent on acoustic-phonetic contextual factors, such as speaking rate; these factors alter not only the location of phonetic category boundaries, but also the location of a category' s best exemplars. The purpose of the present investigation, which focused on the voiceless category as specified by voice onset time (VOT), was to determine whether a higher order linguistic contextual factor, lexical status, which is known to alter the location of the voiced-voiceless phonetic category boundary, also alters the location of the best exemplars of the voiceless category. The results indicated that lexical status has a more limited and qualitatively different effect on the category' s best exemplars than does the acousticphonetic factor of speaking rate. This dissociation is discussed in terms of a production-based account in which perceived best exemplars of a category track contextual variation in speech production.