Japanese mora-timing: a review

Functional timing or rhythmical timing, or both? A corpus study of English and Mandarin duration

It has been long held that languages of the world are divided into rhythm classes so that they are either stress-timed, syllable-timed or mora-timed. It is also known for a long time that duration serves various informational functions in speech. But it is unclear whether these two kinds of uses of duration are complementary to each other, or they are actually one and the same. There has been much empirical research that raises questions about the rhythm class hypothesis due to lack of evidence of the suggested isochrony in any language. Yet the alleged cross-language rhythm classification is still widely taken for granted and continues to be researched. Here we conducted a corpus study of English, an archetype of a stress-timed language, and Mandarin, an alleged syllable-timed language, to look for evidence of at least a tendency toward isochrony when much of the informational use of duration is controlled for. We examined the relationship between segment and syllable duration and the relationship of syllable and phrase duration in the two languages. The results show that in English syllables are largely incompressible to allow stress-timing because segment duration is inflexible to allow variable syllable duration beyond its functional use. Surprisingly, Mandarin does show a small tendency toward both equal syllable duration and equal phrase duration. Additionally, the duration of pre-boundary syllables in English increases linearly with break index, whereas in Mandarin, the duration increase stops after break index 2, which is accompanied by the insertion of silent pauses. We conclude, therefore, timing and duration in speech are predominantly used for encoding information rather being controlled by a rhythmic principle, and the residual equal-duration tendency in the two languages examined here show exactly the opposite patterns from the predictions of the rhythm class hypothesis.

Language specificity in cortical tracking of speech rhythm at the mora, syllable, and foot levels

Recent research shows that adults’ neural oscillations track the rhythm of the speech signal. However, the extent to which this tracking is driven by the acoustics of the signal, or by language-specific processing remains unknown. Here adult native listeners of three rhythmically different languages (English, French, Japanese) were compared on their cortical tracking of speech envelopes synthesized in their three native languages, which allowed for coding at each of the three language’s dominant rhythmic unit, respectively the foot (2.5 Hz), syllable (5 Hz), or mora (10 Hz) level. The three language groups were also tested with a sequence in a non-native language, Polish, and a non-speech vocoded equivalent, to investigate possible differential speech/nonspeech processing. The results first showed that cortical tracking was most prominent at 5 Hz (syllable rate) for all three groups, but the French listeners showed enhanced tracking at 5 Hz compared to the English and the Japanese groups. Second, across groups, there were no differences in responses for speech versus non-speech at 5 Hz (syllable rate), but there was better tracking for speech than for non-speech at 10 Hz (not the syllable rate). Together these results provide evidence for both language-general and language-specific influences on cortical tracking.

Characteristics of Japanese Electrolaryngeal Speech Produced by Untrained Speakers: An Observational Study Involving Healthy Volunteers

Purpose The aim of this study was to investigate the characteristics of electrolaryngeal (EL) speech among untrained speakers to aid in its effective introduction and to identify syllables and words that are easy or difficult to pronounce. Method A total of 21 healthy individuals who had never used an EL were included. The participants were briefed, and tests comprising 100 Japanese syllables and 50 single words were conducted to evaluate EL speech intelligibility. A trained speaker was defined as a certified speech-language pathologist who underwent EL training for 3 months. A 5-point electrolarynx effectivity score (EES) was used for the subjective assessment of EL. Results The median (interquartile range) intelligibility scores of the untrained and trained groups were 24.0% (20.0%-34.0%) and 40.0% (36.0%-45.0%) for syllables and 48.0% (38.0%-60.0%) and 88.0% (82.0%-90.0%) for words, respectively. The intelligibility scores for syllables and words were higher in the trained group than those in the untrained group. Only two syllable subgroups (/m/ and /w/) had > 80% correct answers among untrained speakers. A total of 14 syllable subgroups (/k, kʲ, s, ɕ, t, t͡ɕ, ts, ɲ, h, ç, ɸ, p, pʲ, and a/), a number of which contained voiceless consonants, had < 40% correct answers among both speaker groups. A greater number of morae were associated with higher intelligibility scores. An EES of 4, indicating that the EL was effective, was the most frequent score. Conclusions It was difficult for untrained speakers to produce intelligible speech using an EL. Syllables, including voiceless consonants, were difficult to pronounce using an EL. Longer words with a greater number of morae were more intelligible, even for untrained EL speakers. Supplemental Material https://doi.org/10.23641/asha.16632622.

Post-treatment clinical course following botulinum toxin injection therapy for adductor spasmodic dysphonia: Analysis of data from a placebo-controlled, randomized, double-blinded clinical trial in Japan

OBJECTIVE

Botulinum toxin (BT) therapy is a first-line treatment for spasmodic dysphonia (SD). However, a detailed chronological course and clinical factors that affect the therapeutic effect have been vague. In this study, we analyzed the data from our placebo-controlled, randomized, double-blinded parallel-group comparison/open-label clinical trial of BT (Botox) to clarify these.

METHODS

A total of 22 patients with abductor SD (ADSD) were enrolled. The female-to-male ratio was 20:2 with a mean age of 40.0 ± 10.3 years and a median duration of symptoms of 7.5 years. The therapeutic effect was evaluated based on the change in the number of aberrant morae (phonemes), GRBAS scale, Voice Handicap Index (VHI), and Visual Analogue Scale (VAS).

RESULTS

The change in the number of aberrant morae peaked at 2 weeks and lasted for 12 weeks in the BT group with significance (P < .01) compared to the placebo group. Objective improvement (number of aberrant morae and [S] element in GRBAS) preceded subjective improvement (VHI and VAS). The change in number of aberrant morae and VHI showed a significant correlation (P < .01). The changes in the number of aberrant morae, VHI, and VAS in younger subjects were greater than in older subjects. Patients who presented with post-treatment breathy hoarseness or dysphagia showed better therapeutic effects.

CONCLUSIONS

BT therapy was effective for ADSD based on both objective and subjective assessments. Improvements in subjective parameters were delayed compared to objective measures due to post-treatment breathy hoarseness. However, this adverse event was believed to reflect the treatment effect.

LEVEL OF EVIDENCE

1b.

Botulinum toxin injection into the intrinsic laryngeal muscles to treat spasmodic dysphonia: A multicenter, placebo-controlled, randomized, double-blinded, parallel-group comparison/open-label clinical trial

Background and purpose

Botulinum toxin (BT) injection into the laryngeal muscles has been a standard treatment for spasmodic dysphonia (SD). However, few high‐quality clinical studies have appeared, and BT is used off‐label in most countries.

Methods

We performed a multicenter, placebo‐controlled, randomized, double‐blinded, parallel‐group comparison/open‐label clinical trial to obtain approval for BT (Botox) therapy in Japan. Twenty‐four patients (22 with adductor SD and two with abductor SD) were enrolled. The primary end point was the change in the number of aberrant morae (phonemes) at 4 weeks after drug injection. The secondary end points included the change in the number of aberrant morae, GRBAS scale, Voice Handicap Index (VHI), and visual analog scale (VAS) over the entire study period.

Results

In the adductor SD group, the number of aberrant morae at 4 weeks after injection was reduced by 7.0 ± 2.30 (mean ± SE) in the BT group and 0.2 ± 0.46 in the placebo group (p = 0.0148). The improvement persisted for 12 weeks following BT injections. The strain element in GRBAS scale significantly reduced at 2 weeks after BT treatment. The VHI and VAS scores as subjective parameters also improved. In the abductor SD group, one patient responded to treatment. Adverse events included breathy hoarseness (77.3%) and aspiration when drinking (40.9%) but were mild and resolved in 4 weeks.

Conclusions

Botulinum toxin injection was safe and efficacious for the treatment of SD. Based on these results, BT injection therapy was approved as an SD treatment in Japan.

Effects of Surprisal and Entropy on Vowel Duration in Japanese

Research on English and other languages has shown that syllables and words that contain more information tend to be produced with longer duration. This research is evolving into a general thesis that speakers articulate linguistic units with more information more robustly. While this hypothesis seems plausible from the perspective of communicative efficiency, previous support for it has come mainly from English and some other Indo-European languages. Moreover, most previous studies focus on global effects, such as the interaction of word duration and sentential/semantic predictability. The current study is focused at the level of phonotactics, exploring the effects of local predictability on vowel duration in Japanese, using the Corpus of Spontaneous Japanese. To examine gradient consonant-vowel phonotactics within a consonant-vowel-mora, consonant-conditioned Surprisal and Shannon Entropy were calculated, and their effects on vowel duration were examined, together with other linguistic factors that are known from previous research to affect vowel duration. Results show significant effects of both Surprisal and Entropy, as well as notable interactions with vowel length and vowel quality. The effect of Entropy is stronger on peripheral vowels than on central vowels. Surprisal has a stronger positive effect on short vowels than on long vowels. We interpret the main patterns and the interactions by conceptualizing Surprisal as an index of motor fluency and Entropy as an index of competition in vowel selection.

Fetal rhythm-based language discrimination: a biomagnetometry study

Using fetal biomagnetometry, this study measured changes in fetal heart rate to assess discrimination of two rhythmically different languages (English and Japanese). Two-minute passages in English and Japanese were read by the same female bilingual speaker. Twenty-four mother-fetus pairs (mean gestational age=35.5 weeks) participated. Fetal magnetocardiography was recorded while the participants were presented first with passage 1, a passage in English, and then, following an 18 min interval, with passage 2, either a different passage in English (English-English condition: N=12) or in Japanese (English-Japanese condition: N=12). The fetal magnetocardiogram was reconstructed following independent components analysis decomposition. The mean interbeat intervals were calculated for a 30 s baseline interval directly preceding each passage and for the first 30 s of each passage. We then subtracted the mean interbeat interval of the 30 s baseline interval from that of the first 30 s interval, yielding an interbeat interval change value for each passage. A significant interaction between condition and passage indicated that the English-Japanese condition elicited a more robust interbeat interval change for passage 2 (novelty phase) than for passage 1 (familiarity phase), reflecting a faster heart rate during passage 2, whereas the English-English condition did not. This effect indicates that fetuses are sensitive to the change in language from English to Japanese. These findings provide the first evidence for fetal language discrimination as assessed by fetal biomagnetometry and support the hypothesis that rhythm constitutes a prenatally available building block in language acquisition.

Recoverability-driven coarticulation: Acoustic evidence from Japanese high vowel devoicing

High vowel devoicing in Japanese, where /i, u/ in a C₁VC₂ sequence devoice when both C₁ and C₂ are voiceless, has been studied extensively, but factors that contribute to the devoiced vowels' likelihood of complete deletion is still debated. This study examines the effects of phonotactic predictability on the deletion of devoiced vowels. Native Tokyo Japanese speakers (N = 22) were recorded in a sound-attenuated booth reading sentences containing lexical stimuli. C₁ of the stimuli were /k, ʃ/, after which either high vowel can occur, and /ʧ, ϕ, s, ç/, after which only one of the two occurs. C₂ was always a stop. C₁ duration and center of gravity (COG), the amplitude weighted mean of frequencies present in a signal, were measured. Duration results show that devoicing lengthens only non-fricatives, while it has either no effect or a shortening effect on fricatives. COG results show that coarticulatory effects of devoiced vowels are evident in /k, ʃ/ but not in /ʧ, ϕ, s, ç/. Devoiced high vowels, therefore, seem to be more likely to delete when the vowel is phonotactically predictable than when it is unpredictable.

Durational compensation within a CV mora in spontaneous Japanese: Evidence from the Corpus of Spontaneous Japanese

Previous experimental studies showed that in Japanese, vowels are longer after shorter onset consonants; there is durational compensation within a CV-mora. In order to address whether this compensation occurs in natural speech, this study re-examines this observation using the Corpus of Spontaneous Japanese. The results, which are based on more than 200 000 CV-mora tokens, show that there is a negative correlation between the onset consonant and the following vowel in terms of their duration. The statistical significance of this negative correlation is assessed by a traditional correlation analysis as well as a bootstrap resampling analysis, which both show that it is unlikely that the observed compensation effect occurred by chance. The compensation is not perfect, however, suggesting that it is a stochastic tendency rather than an absolute principle. This paper closes with a discussion of potential factors that may interact with the durational compensation effect.

Domain-general mechanisms for speech segmentation: The role of duration information in language learning

Speech segmentation is supported by multiple sources of information that may either inform language processing specifically, or serve learning more broadly. The Iambic/Trochaic Law (ITL), where increased duration indicates the end of a group and increased emphasis indicates the beginning of a group, has been proposed as a domain-general mechanism that also applies to language. However, language background has been suggested to modulate use of the ITL, meaning that these perceptual grouping preferences may instead be a consequence of language exposure. To distinguish between these accounts, we exposed native-English and native-Japanese listeners to sequences of speech (Experiment 1) and nonspeech stimuli (Experiment 2), and examined segmentation using a 2AFC task. Duration was manipulated over 3 conditions: sequences contained either an initial-item duration increase, or a final-item duration increase, or items of uniform duration. In Experiment 1, language background did not affect the use of duration as a cue for segmenting speech in a structured artificial language. In Experiment 2, the same results were found for grouping structured sequences of visual shapes. The results are consistent with proposals that duration information draws upon a domain-general mechanism that can apply to the special case of language acquisition.

This study shows that adults prefer to group both sequences of shapes and sequences of speech with the final item as the one that has the longest duration. This suggests that final-item duration increase is a helpful cue for perceptual grouping in multiple domains—not just language processing. By testing native speakers of languages that use duration differently, we also show that this grouping preference does not arise from language experience.

Effect of Phonotactic Constraints on Second Language Speech Processing

In this study, we examined whether phonotactic constraints of the first language affect speech processing by Japanese learners of English and whether their proficiency of the second language influences it. Native English speakers and second language speakers with a high level of language proficiency and those with a low level took part in a monitoring task. They were given two kinds of sound stimuli as target syllables (i.e., consonant–vowel and consonant–vowel–consonant) and were asked to detect them in lists of words that have stress on the first or second syllable (e.g., biscuit and beside). The results showed that both stress and phonotactics facilitated segmentation strategies by the three groups. The Japanese groups did not rely on either phonotactics or morae to segment the target syllables. They rather used stress to detect the target syllables in the English words, which is a different segmentation strategy from their first language. This study showed that phonotactic constraints did not interfere with second language processing by native Japanese speakers and provided evidence that second language speakers use the segmentation strategy that is used by native speakers of the target language.

The Emergence of a Phoneme-Sized Unit in L2 Speech Production: Evidence from Japanese-English Bilinguals

Recent research has revealed that the way phonology is constructed during word production differs across languages. Dutch and English native speakers are suggested to incrementally insert phonemes into a metrical frame, whereas Mandarin Chinese speakers use syllables and Japanese speakers use a unit called the mora (often a CV cluster such as "ka" or "ki"). The present study is concerned with the question how bilinguals construct phonology in their L2 when the phonological unit size differs from the unit in their L1. Japanese-English bilinguals of varying proficiency read aloud English words preceded by masked primes that overlapped in just the onset (e.g., bark-BENCH) or the onset plus vowel corresponding to the mora-sized unit (e.g., bell-BENCH). Low-proficient Japanese-English bilinguals showed CV priming but did not show onset priming, indicating that they use their L1 phonological unit when reading L2 English words. In contrast, high-proficient Japanese-English bilinguals showed significant onset priming. The size of the onset priming effect was correlated with the length of time spent in English-speaking countries, which suggests that extensive exposure to L2 phonology may play a key role in the emergence of a language-specific phonological unit in L2 word production.

Taiwanese Learners’ Durational Patterns for Japanese Obstruent Geminates/Singletons and Adjacent Vowels1

This study measured the durations of Japanese obstruent geminates/singletons and their adjacent vowels (V1 and V2) embedded in words repeatedly spoken by four intermediate-level Taiwanese learners of Japanese. The results indicated that the four learners were more or less at a native-like level in terms of geminate lengthening, but not in terms of the V1/V2 duration ratio. These findings suggest that for Chinese learners of Japanese, the learning of Japanese geminates consists of two stages: geminate/singleton phonemic contrast learning, followed by V1/V2 phonetic contrast learning. It is suggested that explicit instruction may be effective at the second stage.

Enhanced musical rhythmic perception in Turkish early and late learners of German

As language rhythm relies partly on general acoustic properties, such as intensity and duration, mastering two languages with distinct rhythmic properties (i.e., stress position) may enhance musical rhythm perception. We investigated whether competence in a second language (L2) with different rhythmic properties than a L1 affects musical rhythm aptitude. Turkish early (TELG) and late learners (TLLG) of German were compared to German late L2 learners of English (GLE) regarding their musical rhythmic aptitude. While Turkish and German present distinct linguistic rhythm and metric properties, German and English are rather similar in this regard. To account for inter-individual differences, we measured participants' short-term and working memory (WM) capacity, melodic aptitude, and time they spent listening to music. Both groups of Turkish L2 learners of German perceived rhythmic variations significantly better than German L2 learners of English. No differences were found between early and late learners' performance. Our findings suggest that mastering two languages with different rhythmic properties enhances musical rhythm perception, providing further evidence of shared cognitive resources between language and music.

Production of single and geminate stops in Japanese three- and four-mora words

This study examined the durational structure of single and geminate stop distinction produced in three- and four-mora words of Japanese, (C(1))V(1)(C(2))C(2)V(2)X [(C(2))C(2) = the contrasting consonants; X = a CV mora, the moraic nasal, or a long vowel as part of V(2)]. The questions addressed were how factors such as speaking rate, segmental variability, and moraic composition of words affected the stop quantity distinction in words longer than well-studied disyllabic words, and whether there exists an invariant parameter that classified these two stop categories. Results showed that all of those factors systematically affected the duration of the contrasting stop closure, the unit of [(C(1))V(1)(C(2))C(2)V(2)], and the entire three- and four-mora words. However, the durational units of moras and words were well-structured, and the ratio of the contrasting stop closure to the [(C(1))V(1)(C(2))C(2)V(2)] unit, as well as the ratio of the closure to the entire word, were found to be invariant in indicating the stop quantity distinction. These results support the theory of relational acoustic invariance [Pickett et al., Phonetica 56, 135-157 (1999)] on the part of production. Furthermore, the results provide insight into different versions of Japanese mora hypothesis [Han, The Study of Sounds 10, 65-80 (1962); Port et al., J. Acoust. Soc. Am. 81(5), 1574-1585 (1987)], which have been under debate for five decades.

Perception and production boundaries between single and geminate stops in Japanese

The theory of relational acoustic invariance [Pickett, E. R., et al. (1999). Phonetica 56, 135-157] was tested with the Japanese stop quantity distinction in disyllables spoken at various rates. The questions were whether the perceptual boundary between the two phonemic categories of single and geminate stops is invariant across rates, and whether there is a close correspondence between the perception and production boundaries. The durational ratio of stop closure to word (where the "word" was defined as disyllables) was previously found to be an invariant parameter that classified the two categories in production, but the present study found that this ratio varied with different speaking rates in perception. However, regression and discriminant analyses of perception and production data showed that treating stop closure as a function of word duration with an intercept term represented the perception and production boundaries very well. This result indicated that the durational ratio of adjusted stop closure (i.e., closure with an added constant) to the word was invariant and distinguished the two phonemic categories clearly. Taken together, the results support the relational acoustic invariance theory, and help refine the theory with regard to exactly what form 'invariance' can take.

Comprehension of degraded speech sounds with m-sequence modulation: an fMRI study

In a recent electroencephalography (EEG) study (Takeichi et al., 2007a), we developed a new technique for assessing speech comprehension using speech degraded by m-sequence modulation and found a correlation peak with a 400-ms delay. This peak depended on the comprehensibility of the modulated speech sounds. Here we report the results of a functional magnetic resonance imaging (fMRI) experiment comparable to our previous EEG experiment. We examined brain areas related to verbal comprehension of the modulated speech sound to examine which neural system processes this modulated speech. A non-integer, alternating-block factorial design was used with 23 Japanese-speaking participants, with time reversal and m-sequence modulation as factors. A main effect of time reversal was found in the left temporal cortex along the superior temporal sulcus (BA21 and BA39), left precentral gyrus (BA6) and right inferior temporal gyrus (BA21). A main effect of modulation was found in the left postcentral gyrus (BA43) and the right medial frontal gyri (BA6) as an increase by modulation and in the left temporal cortex (BA21, 39), parahippocampal gyrus (BA34), posterior cingulate (BA23), caudate and thalamus and right superior temporal gyrus (BA38) as a decrease by modulation. An interaction effect associated specifically with non-modulated speech was found in the left frontal gyrus (BA47), left occipital cortex in the cuneus (BA18), left precuneus (BA7, 31), right precuneus (BA31) and right thalamus (forward>reverse). The other interaction effect associated specifically with modulation of speech sound was found in the inferior frontal gyrus in the opercular area (BA44) (forward>reverse). Estimated scalp projection of the component correlation function (Cao et al., 2002) for the corresponding EEG data (Takeichi et al., 2007a, showed leftward dominance. Hence, activities in the superior temporal sulcus (BA21 and BA39), which are commonly observed for speech processing, as well as left precentral gyrus (BA6) and left inferior frontal gyrus in the opercular area (BA44) is suggested to contribute to the comprehension-related EEG signal.

Tongue movement kinematics in long and short Japanese consonants

This paper examines tongue movements in stop and fricative consonants where the duration of the oral closure/constriction for the consonant is varied for linguistic purposes. Native speakers of Japanese served as subjects. The linguistic material consisted of Japanese word pairs that only differed in the duration of the lingual consonant, which was either long or short. Recordings were made of tongue movements using a magnetometer system. Results show a robust difference in closure duration between the long and short consonants. Overall, the path of the tongue movement during the consonant was longer for the long than for the short consonant. All speakers decreased the speed of the tongue movement during the long consonant. These adjustments in tongue movements were most likely made to maintain the contact between the tongue and the palate for the closure and constriction.

The functional unit in phonological encoding: evidence for moraic representation in native Japanese speakers

Speech production studies have shown that the phonological form of a word is made up of phonemic segments in stress-timed languages (e.g., Dutch) and of syllables in syllable-timed languages (e.g., Chinese). To clarify the functional unit of mora-timed languages, the authors asked native Japanese speakers to perform an implicit priming task (A. S. Meyer, 1990, 1991). In Experiment 1, participants could speed up their production latencies when initial consonant and vowel (CV) of a target word were known in advance but failed to do so when the vowel was unknown. In Experiment 2, prior knowledge of the consonant and glide (Cj) produced no significant priming effect. However, in Experiment 3, significant effects were found for the consonant-vowel coupled with a nasal coda (CVN) and the consonant with a diphthong (CVV), compared with the consonant-vowel alone (CV). These results suggest that the implicit priming effects for Japanese are closely related to the CV-C and CV-V structure, called the mora. The authors discuss cross-linguistic differences in the phonological representation involved in phonological encoding, within current theories of word production.

Effects of speaking rate on the single/geminate stop distinction in Japanese

This study addressed an issue in the theory of acoustic invariance. The question was whether an invariant acoustic property exists for distinguishing Japanese single and geminate voiceless stops across rates and speakers. Four native Japanese speakers produced disyllabic words with single and geminate stops (e.g., /kako/ and /kak:o/) spoken in a carrier sentence at three speaking rates. Durations of sentences, words, stop closures, vowels preceding the contrasting stops, and voice onset times were measured. Ratios of geminate to single stop closures, geminate words to singleton words, closures to preceding vowels, and closures to words were calculated. The effect of rate on closure duration was to yield overlap between the singleton and geminate categories, and to lengthen geminate closures more than single closures as rate decreased. However, the ratio of geminate to single closure duration was unaffected by rate. Furthermore, the ratio of closure to word duration (0.35 as an optimal boundary) best classified all singleton and geminate tokens with 95.7%-98% accuracy. Thus, in spite of overlap in absolute closure duration between single and geminate voiceless stops, there is a relationally invariant measure that divides the two phonemic categories across rates and speakers, supporting the theory of relational acoustic invariance. co ustical Society of America.

Frequency of occurrence for units of phonemes, morae, and syllables appearing in a lexical corpus of a Japanese newspaper

On the basis of the lexical corpus created by Amano and Kondo (2000), using the Asahi newspaper, the present study provides frequencies of occurrence for units of Japanese phonemes, morae, and syllables. Among the five vowels, /a/ (23.42%), /i/ (21.54%), /u/ (23.47%), and /o/ (20.63%) showed similar frequency rates, whereas /e/ (10.94%) was less frequent. Among the 12 consonants, /k/ (17.24%), /t/ (15.53%), and /r/ (13.11%) were used often, whereas /p/ (0.60%) and /b/ (2.43%) appeared far less frequently. Among the contracted sounds, /sj/ (36.44%) showed the highest frequency, whereas /mj/ (0.27%) rarely appeared. Among the five long vowels, /aR/ (34.4%) was used most frequently, whereas /uR/ (12.11%) was not used so often. The special sound /N/ appeared very frequently in Japanese. The syllable combination /k/+V+/N/ (19.91%) appeared most frequently among syllabic combinations with the nasal /N/. The geminate (or voiceless obstruent) /Q/, when placed before the four consonants /p/, /t/, /k/, and /s/, appeared 98.87% of the time, but the remaining 1.13% did not follow the definition. The special sounds /R/, /N/, and /Q/ seem to appear very frequently in Japanese, suggesting that they are not special in terms of frequency counts. The present study further calculated frequencies for the 33 newly and officially listed morae/syllables, which are used particularly for describing alphabetic loanwords. In addition, the top 20 bi-mora frequency combinations are reported. Files of frequency indexes may be downloaded from the Psychonomic Society Web archive at http://www.psychonomic.org/archive/.

Plasticity of the human auditory cortex induced by discrimination learning of non-native, mora-timed contrasts of the Japanese language

In this magnetoencephalographic (MEG) study, we examined with high temporal resolution the traces of learning in the speech-dominant left-hemispheric auditory cortex as a function of newly trained mora-timing. In Japanese, the "mora" is a temporal unit that divides words into almost isochronous segments (e.g., na-ka-mu-ra and to-o-kyo-o each comprises four mora). Changes in the brain responses of a group of German and Japanese subjects to differences in the mora structure of Japanese words were compared. German subjects performed a discrimination training in 10 sessions of 1.5 h each day. They learned to discriminate Japanese pairs of words (in a consonant, anni-ani; and a vowel, kiyo-kyo, condition), where the second word was shortened by one mora in eight steps of 15 msec each. A significant increase in learning performance, as reflected by behavioral measures, was observed, accompanied by a significant increase of the amplitude of the Mismatch Negativity Field (MMF). The German subjects' hit rate for detecting durational deviants increased by up to 35%. Reaction times and MMF latencies decreased significantly across training sessions. Japanese subjects showed a more sensitive MMF to smaller differences. Thus, even in young adults, perceptual learning of non-native mora-timing occurs rapidly and deeply. The enhanced behavioral and neurophysiological sensitivity found after training indicates a strong relationship between learning and (plastic) changes in the cortical substrate.