Effects Of Talker Variability Research Articles

The effect of talker variability on word recognition in preschool children.

The effect of talker variability on word recognition in preschool children.

The effect of talker variability on word recognition in preschool children.

In a series of experiments, the authors investigated the effects of talker variability on children's word recognition. In Experiment 1, when stimuli were presented in the clear, 3- and 5-year-olds were less accurate at identifying words spoken by multiple talkers than those spoken by a single talker when the multiple-talker list was presented first. In Experiment 2, when words were presented in noise, 3-, 4-, and 5-year-olds again performed worse in the multiple-talker condition than in the single-talker condition, this time regardless of order; processing multiple talkers became easier with age. Experiment 3 showed that both children and adults were slower to repeat words from multiple-talker than those from single-talker lists. More important, children (but not adults) matched acoustic properties of the stimuli (specifically, duration). These results provide important new information about the development of talker normalization in speech perception and spoken word recognition.

Talker variability effects on spoken word recall: Encoding or rehearsal?

The effects of talker variability were examined for spoken word recall. In this study, a serial word recall paradigm was used, with talker variability manipulated using single‐ and multiple‐talker lists and with presentation rate varied using fast and slow conditions. In addition, memory rehearsal processes were examined via a continuous distractor task. Under no‐distractor conditions, the results showed that primacy recall performance was better for single‐talker lists compared to multiple‐talker lists. Under distractor conditions, when presentation rate was fast, this difference remained. However, when presentation rate was slow, there was little difference in recall for single‐talker versus multiple‐talker lists. These results will be discussed in terms of the roles of rehearsal and encoding processes in the transfer of voice information to episodic memory for spoken words. [Work supported by NIH Grant No. DCO1667‐03.]

The effects of talker variability across CV and VC environments

A consonantal speeded classification task was used to assess the effects of talker variability across CV and VC environments. In addition, conditions were blocked by syllable type (CV or VC) or consisted of mixed sets of CV and VC syllables. Talker variability was manipulated by presenting stimuli spoken by a single talker or by many talkers. The results showed that the magnitude of the effect of talker variability was approximately the same when comparing performance across talker contexts for CV’s and VC’s. In addition, the talker variability effect was stronger under conditions where syllables were blocked. The results provide further information about the underlying mechanisms involved in processing perceptual variation in the speech signal.

Effects of rate and talker variability on the recall of spoken words.

Changes in speaking rate and talker characteristics have profound effects on the acoustic structure of the speech signal. Current models of speech perception hypothesize that listeners must compensate for changes in rate and talker with a normalization process in which phonetic segments are evaluated relative to the prevailing rate of articulation and relative to specific talker characteristics. The present study was conducted to investigate how listeners adjust or normalize for changes in rate of speech and talker characteristics. A serial recall task was used to evaluate the consequences of rate and talker variability on the early encoding and rehearsal of the spoken words. Listeners were asked to recall words from single versus multiple rate lists; from single versus multiple talker lists; and finally, from lists with words produced by multiple talkers at multiple speaking rates. The results showed that words from lists produced at a single articulation rate were recalled more accurately in early serial positions than words from lists produced at multiple articulation rates; words from lists produced by a single talker were recalled more accurately in early serial positions than words from lists produced by multiple talkers; and finally, the combination of variability in talker and rate did not impair recall relative to lists with variation in rate or talker alone. These findings replicate and extend the results of previous research on talker variability [C. S. Martin etal., J. Exp. Psych:Learn. Mem. Cog. 15, 676–684 (1989); S. D. Goldinger etal., J. Exp. Psych:Learn. Mem. Cog. 17, 152–162 (1991)] suggesting that variations in speaking rate and in talker characteristics incur a processing cost that affects the initial encoding and subsequent rehearsal of spoken words. [Research supported by NIH.]

The effects of speaking rate and amplitude variability on perceptual identification.

Considerable evidence now exists [J. L. Miller, Phonetica 38, 159–180 (1981)] that the temporal properties of speech signals convey phonetic information in a rate-dependent manner. Although most recent models of speech perception have incorporated a stage at which listeners perceptually compensate for variations in articulation rate, as well as other linguistically important sources of variability, they have universally failed to specify whether there are perceptual costs associated with this ‘‘normalization’’ process. The present study was designed to determine whether open-set word identification is influenced by two sources of naturally occurring variability in the speech signal−differences in rate of articulation and overall stimulus amplitude. These two types of variability were chosen because the former is known to be important for phonetic judgments while the latter is generally considered phonetically irrelevant. The results demonstrated that identification of monosyllabic words was significantly poorer when the items were presented in lists containing three, as opposed to one, speaking rates. In contrast, identification accuracy was not significantly affected by the introduction of variability in overall amplitude. These findings extend the results of previous investigations [J. W. Mullenix and D. B. Pisoni, J. Acoust. Soc. Am. 85, 365–378 (1989)] that demonstrated detrimental effects of talker variability for word recognition and further suggest that only variations along phonetically relevant dimensions are likely to result in poorer identification performance. [Work supported by NIH.]

On the nature of talker variability effects on recall of spoken word lists.

In a recent study, Martin, Mullennix, Pisoni, and Summers (1989) reported that subjects' accuracy in recalling lists of spoken words was better for words in early list positions when the words were spoken by a single talker than when they were spoken by multiple talkers. The present study was conducted to examine the nature of these effects in further detail. Accuracy of serial-ordered recall was examined for lists of words spoken by either a single talker or by multiple talkers. Half the lists contained easily recognizable words, and half contained more difficult words, according to a combined metric of word frequency, lexical neighborhood density, and neighborhood frequency. Rate of presentation was manipulated to assess the effects of both variables on rehearsal and perceptual encoding. A strong interaction was obtained between talker variability and rate of presentation. Recall of multiple-talker lists was affected much more than single-talker lists by changes in presentation rate. At slow presentation rates, words in early serial positions produced by multiple talkers were actually recalled more accurately than words produced by a single talker. No interaction was observed for word confusability and rate of presentation. The data provide support for the proposal that talker variability affects the accuracy of recall of spoken words not only by increasing the processing demands for early perceptual encoding of the words, but also by affecting the efficiency of the rehearsal process itself.

On the nature of talker variability effects on recall of spoken word lists.

In a recent study, Martin, Mullennix, Pisoni, and Summers (1989) reported that subjects' accuracy in recalling lists of spoken words was better for words in early list positions when the words were spoken by a single talker than when they were spoken by multiple talkers. The present study was conducted to examine the nature of these effects in further detail. Accuracy of serial-ordered recall was examined for lists of words spoken by either a single talker or by multiple talkers. Half the lists contained easily recognizable words, and half contained more difficult words, according to a combined metric of word frequency, lexical neighborhood density, and neighborhood frequency. Rate of presentation was manipulated to assess the effects of both variables on rehearsal and perceptual encoding. A strong interaction was obtained between talker variability and rate of presentation. Recall of multiple-talker lists was affected much more than single-talker lists by changes in presentation rate. At slow presentation rates, words in early serial positions produced by multiple talkers were actually recalled more accurately than words produced by a single talker. No interaction was observed for word confusability and rate of presentation. The data provide support for the proposal that talker variability affects the accuracy of recall of spoken words not only by increasing the processing demands for early perceptual encoding of the words, but also by affecting the efficiency of the rehearsal process itself.

Hot topics in speech communication

Six hot topics will be described, two topics in each of the following three areas: speech perception, speech production, and signal processing by machines. (1) In speech perception, new studies on the representation of speech suggest that listeners' stored descriptions of phonetic units take the form of a prototype of the speech category. Adult data address the language specificity of prototypes and the effects of contextual factors on prototypes. Infant data address the developmental issue of whether phonetic prototypes are innate or whether they derive from linguistic experience. (2) Also in the area of speech perception, there are new data on the effects of talker variability. Adults, and even young infants, are capable of normalizing the speech produced by different talkers, but listeners at both ages are nonetheless adversely affected by talker variability, suggesting that attentional factors play a role in speech perception. (3) In the area of speech production, there is new emphasis on the study of articulatory timing in speech motor control. The pattern of phase relations between different articulators and its relation to linguistic structure, as well as the general coordination of speech movements, are being investigated. (4) Also in speech production, there are new advances in our understanding of laryngeal mechanisms. These advances stem from models of the glottal volume-velocity source, findings on aerodynamic phenomena at the glottis, and analyses of the mechanical properties of vocal-fold tissue. (5) In the area of signal processing, neural networks are being applied to difficult problems in speech recognition, such as the recognition of phonetic units. Computational models composed of large numbers of interconnected processing elements (nodes) have been successfully applied to the analysis of dynamic information distributed over several phonetic units. (6) Also in signal processing, the application of speech coding to hearing aids and auditory prostheses has resulted in improved speech reception. Cross-fertilization across areas in speech communication has furthered our research endeavors.

Talker variability and word recognition: A developmental perspective

The effects of talker variability on spoken word recognition were studied developmentally in 3‐, 4‐, and 5‐yr‐old children. Subjects listened to lists of words and were required to identify each word by pointing to a picture in a six alternative visual display. The words and pictures were taken from the word intelligibility by picture identification test (WIPI). Three talker conditions were examined: single talker, single talker with varying amplitude, and multiple talker. Each child heard three lists, one from each talker condition, in varying order. Results showed a main effect of age and an interaction between talker condition and list order. As expected, we found an increase in overall accuracy with age. However, the 3‐yr‐olds did better in the single‐talker condition than the other conditions (which did not differ). This was found only when the lists were presented first during a test session. Second and third lists showed no difference due to talker condition. In most of the conditions the 4‐ and 5‐yr‐olds displayed ceiling levels of performance that may have obscured other differences. Further studies are underway with younger children to examine the nature of the differences in perception between single‐talker and multi‐talker lists. [Work supported by NIH Grant DC‐0111‐14 to Indiana Univ.]

Detailing the nature of talker variability effects in speech perception

Previous studies have shown that changes in a talker's voice from stimulus to stimulus affect the perception and recall of spoken words [see Mullennix et al., J. Acoust. Soc. Am. 85, 365–378 (1989); Martin et al., J. Exp. Psychol. Learn. Mem. Cog. (in press)]. In the present study, the perceptual consequences of talker variability were investigated in further detail. In order to assess the relative magnitude of intratrial versus intertrial changes in a talker's voice, a same‐different reaction time judgment task was used. Performance was compared across three talker conditions: single talker, multiple talker across trials, and multiple talker within trials. In addition, the effects of talker variability over time were examined by observing performance across varying ISI delays. The results obtained provide further information about the nature of talker variability effects in the perception of spoken words and will be discussed in terms of their relationship to perceptual normalization processes in speech perception. [Work supported by NIH.]

Effects of talker variability on recall of spoken word lists.

Three experiments were conducted to investigate recall of lists of words containing items spoken by either a single talker or by different talkers. In each experiment, recall of early list items was better for lists spoken by a single talker than for lists of the same words spoken by different talkers. The use of a memory preload procedure demonstrated that recall of visually presented preload digits was superior when the words in a subsequent list were spoken by a single talker than by different talkers. In addition, a retroactive interference task demonstrated that the effects of talker variability on the recall of early list items were not due to use of talker-specific acoustic cues in working memory at the time of recall. Taken together, the results suggest that word lists produced by different talkers require more processing resources in working memory than do lists produced by a single talker. The findings are discussed in terms of the role that active rehearsal plays in the transfer of spoken items into long-term memory and the factors that may affect the efficiency of rehearsal.

Some effects of talker variability on spoken word recognition.

The perceptual consequences of trial-to-trial changes in the voice of the talker on spoken word recognition were examined. The results from a series of experiments using perceptual identification and naming tasks demonstrated that perceptual performance decreases when the voice of the talker changes from trial to trial compared to performance when the voice on each trial remains the same. In addition, the effects of talker variability on word recognition appeared to be more robust and less dependent on task than the effects of word frequency and lexical structure. Possible hypotheses regarding the nature of the processes giving rise to these effects are discussed, with particular attention to the idea that the processing of information about the talker's voice is intimately related to early perceptual processes that extract acoustic-phonetic information from the speech signal.

Effects of talker variability on recall of spoken word lists.

Effects of talker variability on recall of spoken word lists.

Effect of Gas Constants on Voicing Frequency

It is well known that the composition of the exhaled gas has no large effect on voicing periodicity but, so far, the question of small effects has been left open. Mathematical models of vocal-cord action, though admittedly imperfect, nevertheless indicate, by virtue of the fact that the expressions contain gas constants, that some effects might be expected to occur. However, the results of experiments to detect such effects are too greatly influenced by talker variability when conversational speech is used as the test material. The present paper describes an experiment designed to reduce the effect of talker variability. The subject is presented with a complex tone through earphones. It is his task to match the frequency of the tone vocally, but after it has been removed and noise sufficient to mask his own performance substituted on the earphones. Under such conditions, the usual auditory feedback is lacking, and only proprioceptive feedback is available to position and tension the vocal cords. Preliminary results from measuring voicing frequency with various gases will be reported.