Scott E. Lively

Training Japanese listeners to identify English /r/ and /l/: A first report

Native speakers of Japanese learning English generally have difficulty differentiating the phonemes /r/ and /l/, even after years of experience with English. Previous research that attempted to train Japanese listeners to distinguish this contrast using synthetic stimuli reported little success, especially when transfer to natural tokens containing /r/ and /l/ was tested. In the present study, a different training procedure that emphasized variability among stimulus tokens was used. Japanese subjects were trained in a minimal pair identification paradigm using multiple natural exemplars contrasting /r/ and /l/ from a variety of phonetic environments as stimuli. A pretest-posttest design containing natural tokens was used to assess the effects of training. Results from six subjects showed that the new procedure was more robust than earlier training techniques. Small but reliable differences in performance were obtained between pretest and posttest scores. The results demonstrate the importance of stimulus variability and task-related factors in training nonnative speakers to perceive novel phonetic contrasts that are not distinctive in their native language.

Training Japanese listeners to identify English /r/ and /l/. II: The role of phonetic environment and talker variability in learning new perceptual categories

Two experiments were carried out to extend Logan et al.s recent study [J. S. Logan, S. E. Lively, and D. B. Pisoni, J. Acoust. Soc. Am. 89, 874-886 (1991)] on training Japanese listeners to identify English /r/ and /l/. Subjects in experiment 1 were trained in an identification task with multiple talkers who produced English words containing the /r/-/l/ contrast in initial singleton, initial consonant clusters, and intervocalic positions. Moderate, but significant, increases in accuracy and decreases in response latency were observed between pretest and posttest and during training sessions. Subjects also generalized to new words produced by a familiar talker and novel words produced by an unfamiliar talker. In experiment 2, a new group of subjects was trained with tokens from a single talker who produced words containing the /r/-/l/ contrast in five phonetic environments. Although subjects improved during training and showed increases in pretest-posttest performance, they failed to generalize to tokens produced by a new talker. The results of the present experiments suggest that variability plays an important role in perceptual learning and robust category formation. During training, listeners develop talker-specific, context-dependent representations for new phonetic categories by selectively shifting attention toward the contrastive dimensions of the non-native phonetic categories. Phonotactic constraints in the native language, similarity of the new contrast to distinctions in the native language, and the distinctiveness of contrastive cues all appear to mediate category acquisition.

Comprehension of synthetic speech produced by rule: word monitoring and sentence-by-sentence listening times

Previous comprehension studies using postperceptual memory tests have often reported negligible differences in performance between natural speech and several kinds of synthetic speech produced by rule, despite large differences in segmental intelligibility. The present experiments investigated the comprehension of natural and synthetic speech using two different on-line tasks: word monitoring and sentence-by-sentence listening. On-line task performance was slower and less accurate for passages of synthetic speech than for passages of natural speech. Recognition memory performance in both experiments was less accurate following passages of synthetic speech than of natural speech. Monitoring performance, sentence listening times, and recognition memory accuracy all showed moderate correlations with intelligibility scores obtained using the Modified Rhyme Test. The results suggest that poorer comprehension of passages of synthetic speech is attributable in part to the greater encoding demands of synthetic speech. In contrast to earlier studies, the present results demonstrate that on-line tasks can be used to measure differences in comprehension performance between natural and synthetic speech.

On Prototypes and Phonetic Categories: A Critical Assessment of the Perceptual Magnet Effect in Speech Perception

According to P. K. Kuhl (1991), a perceptual magnet effect occurs when discrimination accuracy is lower among better instances of a phonetic category than among poorer instances. Three experiments examined the perceptual magnet effect for the vowel /i/. In Experiment 1, participants rated some examples of /i/ as better instances of the category than others. In Experiment 2, no perceptual magnet effect was observed with materials based on Kuhls tokens of /i/ or with items normed for each participant. In Experiment 3, participants labeled the vowels developed from Kuhls test set. Many of the vowels in the nonprototype /i/ condition were not categorized as /i/s. This finding suggests that the comparisons obtained in Kuhls original study spanned different phonetic categories.

An examination of the perceptual magnet effect

Recently, Kuhl [Pecept. Psychophys. 50, 93–107 (1991)] has argued that speech perception is guided by phonetic prototypes that are assumed to be stored in long‐term memory. This claim is based on the finding of a ‘‘perceptual magnet effect.’’ According to Kuhl, speech prototypes act like ‘‘magnets’’ because they attract similar stimuli to themselves. Furthermore, prototypes attract other stimuli more strongly than nonprototypes. Thus vowels that surround a prototypical stimulus are more difficult to discriminate than vowels that surround a nonprototype. Data are presented from vowel ‘‘goodness’’ rating experiments that suggest that listeners’ prototypes for the vowel /i/ may be more extreme and variable than Kuhl’s data indicate. Data are also presented from a categorization experiment that indicates that all of Kuhl’s vowels may not be from the same phonetic category. These findings call into question the basis of the perceptual magnet effect. An alternative interpretation of both sets of findings is giv...

Training listeners to perceive novel phonetic categories: how do we know what is learned?

Logan et al. [J. Acoust. Soc. Am. 89, 874–886 (1991)] carried out a perceptual learning experiment in which Japanese listeners were trained to identify English words containing /r/ and /l/. Pruitt [J. Acoust. Soc. Am. 94 (1993)] has criticized several aspects of the procedures and conclusions. First, he argues that the lack of appropriate control groups make interpretation of the results problematic. Second, he asserts that the generalization test was methodologically flawed. Although Pruitt raises some important issues that are worth pursuing in future research, it is argued that the methodology that was employed and the conclusions that were drawn were valid.

Training Japanese listeners to identify English /r/ and /l/: A replication and extension

Monolingual native speakers of Japanese were trained to identify English /r/ and /l/ using a modified version of Logan, Lively, and Pisoni’s [J. S. Logan et al., J. Acoust. Soc. Am. 89, 874–886 (1991)] high variability training procedure. Both the talker’s voice and the phonetic environment were varied during training. Subjects improved in their ability to identify /r/ and /l/ from the pre‐test to the post‐test and during training. Generalization accuracy depended on the voice of the talker producing the /r/–/l/ contrasts: Subjects were significantly more accurate when words were produced by a familiar talker than when they were produced by an unfamiliar talker. Three months after the conclusion of training, subjects were given the post‐test and the tests of generalization again. Surprisingly, accuracy decreased only slightly on each test, even though no training or exposure to /r/ and /l/ occurred during the 3‐month interval. These results demonstrate that the high variability training paradigm is effect...

Trainlng Japanese listeners to identify /r/ and /l/

Native speakers of Japanese learning English generally have difficulty differentiating the phonemes /r/ and /l/, even after years of experience with English. Previous research that attempted to train Japanese listeners to distinguish this contrast using synthetic stimuli showed little success, especially when transfer to natural tokens containing /r/ and /l/ was tested. In the present study, a procedure that differed from these earlier attempts was used. Japanese subjects were trained in an identification paradigm using as stimuli multiple natural exemplars contrasting /r/ and /l/ from a variety of phonetic environments. A pretest‐posttest design combined with a test of generalization containing novel natural tokens was used to assess the effectiveness of training. Analysis of pilot data from a small group of subjects showed that the new procedure was more robust than earlier procedures. The results demonstrate the importance of stimulus variability and task‐related factors in training second language learners to perceive novel phonemic contrasts that are not distinctive in their native language. [Work supported by NIH.]

On‐line measures of comprehension of natural and synthetic speech

Accumulated perceptual research comparing natural and synthetic speech indicates relatively large differences in tasks assessing acoustic‐phonetic processing, and small differences in tasks assessing higher levels of processing related to comprehension. Studies comparing comprehension of passages of fluent natural and synthetic speech have generally examined performance on questions presented after subjects have listened to a passage. Such postperceptual measures are known to be relatively insensitive to differences in “real‐time” processing operations. The present investigation employed an “on‐line” measure of processing, i.e., word monitoring, to study comprehension. Subjects in these studies were presented with three types of passages—(1) natural speech, (2) high‐quality synthetic speech, and (3) low‐quality synthetic speech—and were required to monitor for target words as well as verify postperceptual comprehension questions. Monitoring latencies and verification performance will be discussed in terms...