Reiko Akahane-Yamada

A perceptual interference account of acquisition difficulties for non-native phonemes

This article presents an account of how early language experience can impede the acquisition of non-native phonemes during adulthood. The hypothesis is that early language experience alters relatively low-level perceptual processing, and that these changes interfere with the formation and adaptability of higher-level linguistic representations. Supporting data are presented from an experiment that tested the perception of English /r/ and /l/ by Japanese, German, and American adults. The underlying perceptual spaces for these phonemes were mapped using multidimensional scaling and compared to native-language categorization judgments. The results demonstrate that Japanese adults are most sensitive to an acoustic cue, F2, that is irrelevant to the English /r/-/l/ categorization. German adults, in contrast, have relatively high sensitivity to more critical acoustic cues. The results show how language-specific perceptual processing can alter the relative salience of within- and between-category acoustic variation, and thereby interfere with second language acquisition.

Training Japanese listeners to identify English /r/and /l /: Long-term retention of learning in perception and production

Previous work from our laboratories has shown that monolingual Japanese adults who were given intensive high-variability perceptual training improved in both perception and production of English /r/-/l/ minimal pairs. In this study, we extended those findings by investigating the long-term retention of learning in both perception and production of this difficult non-native contrast. Results showed that 3 months after completion of the perceptual training procedure, the Japanese trainees maintained their improved levels of performance on the perceptual identification task. Furthermore, perceptual evaluations by native American English listeners of the Japanese trainees’ pretest, posttest, and 3-month follow-up speech productions showed that the trainees retained their long-term improvements in the general quality, identifiability, and overall intelligibility of their English /r/-/l/ word productions. Taken together, the results provide further support for the efficacy of high-variability laboratory speech sound training procedures, and suggest an optimistic outlook for the application of such procedures for a wide range of “special populations.” nt]mis|This work was supported by NIDCD Training Grant DC-00012 and by NIDCD Research Grant DC-00111 to Indiana University.

An investigation of current models of second language speech perception: the case of Japanese adults' perception of English consonants.

This study reports the results of two experiments with native speakers of Japanese. In experiment 1, near-monolingual Japanese listeners participated in a cross-language mapping experiment in which they identified English and Japanese consonants in terms of a Japanese category, then rated the identifications for goodness-of-fit to that Japanese category. Experiment 2 used the same set of stimuli in a categorial discrimination test. Three groups of Japanese speakers varying in English-language experience, and one group of native English speakers participated. Contrast pairs composed of two English consonants, two Japanese consonants, and one English and one Japanese consonant were tested. The results indicated that the perceived phonetic distance of second language (L2) consonants from the closest first language (L1) consonant predicted the discrimination of L2 sounds. In addition, this study investigated the role of experience in learning sounds in a second language. Some of the consonant contrasts tested showed evidence of learning (i.e., significantly higher scores for the experienced than the relatively inexperienced Japanese groups). The perceived phonetic distance of L1 and L2 sounds was found to predict learning effects in discrimination of L1 and L2 sounds in some cases. The results are discussed in terms of models of cross-language speech perception and L2 phonetic learning.

Perceived phonetic dissimilarity and L2 speech learning: the case of Japanese /r/ and English /l/ and /r/

Abstract Previous research has demonstrated that English /r/ is perceptually more dissimilar from Japanese /r/ than English /l/ is for native Japanese (NJ) speakers. It has been proposed by the Speech Learning Model that the more distant an L2 sound (phonetic segment) is from the closest L1 speech sound, the more learnable the L2 sound will be (in: W. Strange (Ed.), Speech Perception and Linguistic Experience: Issues in Cross-language Research, York Press, Timonium, MD, 1995, p. 233). This hypothesis was evaluated in this study by investigating whether NJ speakers will have more success acquiring English /r/ than /l/. A longitudinal study examined the perception (Experiment 1) and production (Experiment 2) of English /l/, /r/, and/w/ by NJ adults and children who were living in the US at the time of testing. The results suggested that there was greater improvement for English /r/ than English /l/ among the NJ children. The NJ childrens discrimination of /l/-/r/ and /r/-/w/ was significantly better at the second testing (T2) than 1 year earlier (T1). The NJ children also showed greater improvement from T1 to T2 in producing /r/ than /l/. The results are taken as support for a hypothesis of the Speech Learning Model (in: W. Strange (Ed.), Speech Perception and Linguistic Experience: Issues in Cross-language Research, York Press, Timonium, MD, 1995, p. 233) that degree of perceived phonetic dissimilarity influences L2 learners’ success in acquiring L2 phonetic segments.

Phonetic perceptual identification by native- and second-language speakers differentially activates brain regions involved with acoustic phonetic processing and those involved with articulatory-auditory/orosensory internal models.

This experiment investigates neural processes underlying perceptual identification of the same phonemes for native- and second-language speakers. A model is proposed implicating the use of articulatory-auditory and articulatory-orosensory mappings to facilitate perceptual identification under conditions in which the phonetic contrast is ambiguous, as in the case of second-language speakers. In contrast, native-language speakers are predicted to use auditory-based phonetic representations to a greater extent for perceptual identification than second-language speakers. The English /r-l/ phonetic contrast, although easy for native English speakers, is extremely difficult for native Japanese speakers who learned English as a second language after childhood. Twenty-two native English and twenty-two native Japanese speakers participated in this study. While undergoing event-related fMRI, subjects were aurally presented with syllables starting with a /r/, /l/, or a vowel and were required to rapidly identify the phoneme perceived by pushing one of three buttons with the left thumb. Consistent with the proposed model, the results show greater activity for second- over native-language speakers during perceptual identification of /r/ and /l/ relative to vowels in brain regions implicated with instantiating forward and inverse articulatory-auditory articulatory-orosensory models [Brocas area, anterior insula, anterior superior temporal sulcus/gyrus (STS/G), planum temporale (PT), superior temporal parietal area (Stp), SMG, and cerebellum]. The results further show that activity in brain regions implicated with instantiating these internal models is correlated with better /r/ and /l/ identification performance for second-language speakers. Greater activity found for native-language speakers especially in the anterior STG/S for /r/ and /l/ perceptual identification is consistent with the hypothesis that native-language speakers use auditory phonetic representations more extensively than second-language speakers.

Learning-induced neural plasticity associated with improved identification performance after training of a difficult second-language phonetic contrast.

Adult native Japanese speakers have difficulty perceiving the English /r-l/ phonetic contrast even after years of exposure. However, after extensive perceptual identification training, long-lasting improvement in identification performance can be attained. This fMRI study investigates localized changes in brain activity associated with 1 month of extensive feedback-based perceptual identification training by native Japanese speakers learning the English /r-l/ phonetic contrast. Before and after training, separate functional brain imaging sessions were conducted for identification of the English /r-l/ contrast (difficult for Japanese speakers), /b-g/ contrast (easy), and /b-v/ contrast (difficult), in which signal-correlated noise served as the reference control condition. Neural plasticity, denoted by exclusive enhancement in brain activity for the /r-l/ contrast, does not involve only reorganization in brain regions concerned with acoustic-phonetic processing (superior and medial temporal areas) but also the recruitment of additional bilateral cortical (supramarginal gyrus, planum temporale, Brocas area, premotor cortex, supplementary motor area) and subcortical regions (cerebellum, basal ganglia, substantia nigra) involved with auditory-articulatory (perceptual-motor) mappings related to verbal speech processing and learning. Contrary to what one may expect, brain activity for perception of a difficult contrast does not come to resemble that of an easy contrast as learning proceeds. Rather, the results support the hypothesis that improved identification performance may be due to the acquisition of auditory-articulatory mappings allowing for perception to be made in reference to potential action.

Cross-language perceptual similarity predicts categorial discrimination of American vowels by naïve Japanese listeners

Current speech perception models propose that relative perceptual difficulties with non-native segmental contrasts can be predicted from cross-language phonetic similarities. Japanese (J) listeners performed a categorical discrimination task in which nine contrasts (six adjacent height pairs, three front/back pairs) involving eight American (AE) vowels [iː, ɪ, ε, æː, ɑː, ʌ, ʊ, uː] in /hVbə/ disyllables were tested. The listeners also completed a perceptual assimilation task (categorization as J vowels with category goodness ratings). Perceptual assimilation patterns (quantified as categorization overlap scores) were highly predictive of discrimination accuracy (r(s)=0.93). Results suggested that J listeners used both spectral and temporal information in discriminating vowel contrasts.

An MRI-based analysis of the English /r/ and /l/ articulations

Midsagittal tongue shapes for sustained English /r/ and /l/ sounds between native speakers of American English (AE) and Japanese were compared using the magnetic resonance imaging (MRI) technique. The /r/ sound as produced by AE speakers was characterized by a constriction at the anterior part of the hard palate and the existence of a sublingual cavity, and for the /l/ sound, apical contact to the front teeth and/or alveolar ridge, and the absence of the sublingual cavity. For Japanese speakers, strategies to form the tongue shape contrast between /r/ and /l/ productions were categorized into four types depending on the type of contact/constriction and presence/absence of the sublingual cavity. The first type showed a pattern of tongue shape similar to AE speakers. The second and third types were characterized by /r/- and /l/-oriented production, respectively, for both sounds. In the last type, the distinction between /r/ and /l/ was formed only by the absence or presence of apical contact, while a sublingual cavity was produced for both sounds. These types are discussed in the context of a perceptual evaluation and an acoustical analysis.

Native and non‐native perception of phonemic length contrasts in Japanese

Segment length is distinctive in Japanese, e.g., /kado/ ‘‘corner’’ versus /ka:do/ ‘‘card,’’ unlike languages such as English. To study this property extensively and precisely, a series of perception experiments were conducted. Stimuli were pairs of unaccented 3‐ or 4‐mora nonsense Japanese words of the basic form /ere——e/ where —— is one of /p t k m n s/. Each pair contrasted in either vowel length, e.g., /erete/ versus /ere:te/, or in consonant length, e.g., /erete/ versus /erette/. Each pair was also embedded within a carrier sentence. A synthetic continuum gradually varying in the duration of the target vowel or consonant was built for each pair using straight, a high‐fidelity speech analysis, synthesis, and manipulation system [Kawahara et al., Speech Commun. 27, 187–207 (1999)]. Native Japanese and native English speakers participated in both identification and discrimination tests of each continuum. Preliminary results from stimuli containing stops indicate that the non‐native discrimination scores ...

Categorial discrimination of English and Japanese vowels and consonants by native Japanese and English subjects

Categorial discrimination tests (CDTs) with equal opportunities for ‘‘hits’’ and ‘‘false alarms’’ assessed native Japanese and English subjects’ perception of English and Japanese segmental contrasts. The stimuli consisted of vowels and consonants spoken at two rates by five native speakers each of English and Japanese. The listeners chose the odd item out in triads, if there was one, or responded ‘‘none’’ if they heard three physically different tokens of a single vowel or consonant. A’ scores were computed for each contrast. The subjects were ten native English (NE) controls, ten ‘‘experienced’’ bilinguals (Japanese speakers who had spent several years in the United States), and ten ‘‘inexperienced’’ bilinguals (Japanese speakers who had never lived outside Japan, but had studied English in school). Analysis of the CDT results will help determine (1) if the subjects differ in their ability to discriminate consonants and vowels, (2) if perceptual sensitivity to vowel and/or consonant contrasts is affecte...