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Neural plasticity revealed in perceptual training of a Japanese adult listener to learn american /l-r/ contrast: a whole-head magnetoencephalography study

Authors:
Neural plasticity revealed in perceptual training of a Japanese adult listener to
learn American /l-r/ contrast: a whole-head magnetoencephalography study
Yang Zhang1, Patricia K. Kuhl1, Toshiaki Imada2&3, Paul Iverson4, John Pruitt5, Makoto Kotani6,
Erica Stevens1
1Department of Speech and Hearing Sciences, University of Washington, Seattle, Washington 98195, USA;
2NTT Communication Science Laboratories Laboratory, 3Real World Computing Partnership, Nippon
Telegraph and Telephone Corporation, Atsugi-shi, Kanagawa 243-0198, Japan; 4Department of Phonetics &
Linguistics, University College London, London NW1 2HE, England; 5Microsoft Corporation, Redmond,
WA 98052, USA; 6Tokyo Denki University, Tokyo, 101-8457, Japan.
ABSTRACT
In this study, behavioral and brain measures were taken to
assess the effects of training a Japanese adult subject to
perceptually distinguish English /l/ and //. Behavioral data
showed significant improvement in identifying both trained and
untrained speech stimuli. Correspondingly, neuromagnetic
results showed enhanced mismatch field responses in the left
hemisphere and reduced activities in the right hemisphere. This
pattern of neural plasticity was not observed for truncated non-
speech stimuli.
1. Introduction
Language experience has a dramatic impact on speech
perception and production. One classic example is that of
Japanese listeners’ poor performance on the English /l-r/
distinction. Early work on developmental speech perception has
demonstrated that at a young age infants are capable of
detecting phonetic differences regardless of the tested language
[1,2]. Evidence of linguistic experience in mapping the sounds
of what will become the native language begins to show up as
early as at six months of age [3], and by the end of the first year
of life, infants have become adult-like in their perception of
speech sounds [4]. Japanese infants were found to be no
exception in the /l/-// case [5,6].
The study of development is one way of exploring how
language experience alters our ability to perceive and produce
speech. A different method is to study the effects of training
adult listeners to perceive non-native speech sounds. The
successes and failures of various training methods may provide
us with a better understanding of the underlying perceptual
mechanisms and the nature of neural plasticity for learning in
the formation of new phonetic categories. Many training studies
using synthetic speech found that despite substantial stimulus-
specific improvement, subjects’ ability to generalize this
training to natural listening situations may remain relatively
poor [7,8]. Some recent training studies using a high-variability
natural-token procedure, however, did show long-term retention
of generalizable training effects in perception as well as
production [9,10]. How to integrate the training methods and
optimize the interactions of stimulus variables, task variables,
and subject characteristics for successful perceptual learning
remains a challenge to researchers [11].
Modern brain imaging and neurophysiological tools provide
good temporal and spatial resolutions suitable for a direct
noninvasive assessment of the neural structures and brain
mechanisms that are responsible for cognitive processes. Recent
works using event related potentials (ERP) and
magnetoencephalography (MEG) indicate that certain
components of neural activity such as mismatch negativity
(MMN) and mismatch field (MMF) reflect not only pre-
attentive sensory detection of small acoustic changes in auditory
stimuli but also a higher level of processing for speech sounds
that involves language-specific representations [12,13,14].
These studies consistently showed that given equalized amount
of acoustic difference for the native and nonnative phonetic
contrasts, the neural mismatch responses for nonnative pair were
significantly diminished. However, it is unclear how a nonnative
phonetic category can be learned and how the internal structure
of the learned phonetic category may influence speech
perception. Recent studies on brain plasticity showed a
promising line of research to address these questions [15].
In this report we describe preliminary results from an ongoing
cross-language project using Functional Magnetic Resonance
Imaging (fMRI) and MEG to investigate brain plasticity in
perceptual training. Given the accuracy of MEG data that is
meaningful on a single-subject level [16], this report looked at
one Japanese listener’s training data and his MMF responses.
2. Methods
2.1 Features of the Training Software Program
A training software program was developed on the basis of
Pruitt’s original work [17]. The program utilizes the following
training methods that are considered to be conducive to speech
and language learning:
1. Use of an identification task. Discrimination task only
focuses on differences between stimuli, which may not
facilitate phonetic categorization.
2. Incremental levels of difficulty. Difficulty is
implemented in the variability of talker, vowel context,
syllabic context, and the amount of acoustic
exaggeration. The use of exaggerated speech is to
mimic the listening experience of infants who are
exposed in great numbers to the exaggerated acoustic
events contained in infant-directed speech (known as
"motherese"). This speaking style consists of greater
acoustic exaggeration and variety than adult-directed
speech and may facilitate the formation of prototypical
representation of a phonetic category [18].
3. Bimodal speech cues. A static photographic image of
each talker articulating /r/ or /l/ was provided
simultaneously for each acoustic presentation.
4. Self-directed, adaptive, motivational training with
immediate feedback. Each correct answer is registered
onscreen and above-chance performance is recognized
with small monetary reward. Incorrect answers are
indicated and prompted with playback.
2.2 Behavioral Experiments
For a baseline measure, ten native speakers of Japanese (3
females, 7 males, age range: 21-24, mean 22.3) and ten native
speakers of American English (5 females, 5 males, age range:
20-30, mean 23.6) were recruited. Japanese subjects were all
college students in Japan who received English instruction in the
mid- and high- school level as well as in college. The American
subjects were monolingual undergraduate students at University
of Washington. All subjects are right-handed with no speech
and hearing disorders in medical history.
A /ra-la/ continuum was created using SenSyn program. Figure
1 shows spectrograms for the endpoints in the continuum. There
were eleven syllables of 400 ms in duration. All acoustic
parameters were kept the same except the F3 transition slope
whose starting frequencies varied in the range of 1325 to 3649
Hz at eleven levels equally spaced on the mel scale. The initial
155 ms of stimuli were composed of steady formant structure.
The F3 transition had 100 ms duration that ended in a steady
third formant at 2973 Hz for /a/. Specific parameters were
adopted from a previous study [19]. The syllables were
resampled to 48 kHz 16-bit using SoundEdit1.6 to accommodate
the stimulator for MEG experiments.
/a/ /la/
Figure1. Schematic spectrograms for the synthetic stimuli.
Subjects completed an identification test in an acoustically
treated booth. The test began with a familiarization session of 11
trials followed by a testing session of 40 trials for each stimulus.
The stimuli were randomly presented to the right-ear headphone
at 80dB SPL. After the test, one Japanese subject was chosen to
complete the training.
2.3 Training Protocol
A pretest-intervention-posttest design was implemented to
assess the listener’s initial capability and the training effects. A
Mac G3 computer was used as the platform for the program.
The subject listened to stimuli via a headset at a comfortable
level. Stimuli were prepared first by recording natural tokens of
/r/ and /l/ from eight native speakers of American English for
five vowels in CV and VCV contexts. These tokens were
submitted to an LPC analysis-resynthesis procedure to
exaggerate the formant frequency differences between pairs of
/r-l/ tokens, and to reduce the bandwidth of F3. Temporal
exaggeration of the /r-l/ stimuli was made to the stimuli using a
time warping technique (pitch synchronous overlap and add).
These acoustically modified stimuli and the digitized versions of
the naturally-produced tokens were used for the training phase
of the experiment, while only the natural tokens were presented
in the pretest and posttest. The pretest consisted of 4 blocks
with 320 tokens by 8 speakers in 80 contexts. The posttest was
identical. Training consisted of twelve sessions of
approximately 50~60 minutes a session. Each session had a total
of 400 listening trials arranged in 10 blocks with short
intermittent tests of 10 trials that assessed progress. The series
of training sessions commenced with presentation of tokens that
were highly exaggerated but progressed over the course of the
training to less exaggerated versions of the tokens. To address
generalizability of training effects to novel /l/ and /r/ sounds,
five talkers were used for training, but tokens from all talkers
were presented in the pre- and posttests. For both pre- and post-
tests, MEG experiments preceded behavioral experiments.
2.4 MEG Experiments
MEG experiments were conducted using the oddball paradigm.
The subject was instructed to read a self-chosen book and ignore
the auditory stimuli. Four conditions were designed to examine
neural correlates of discrimination and categorization.
1. Single condition. The endpoint stimuli in the continuum
were used for standard and deviant. This pair maximizes
the acoustic difference between /l/ and /r/.
2. Multiple condition. Three stimuli from each category in
the continuum were used for standard and deviant.
3. Truncated 155ms condition. The initial 155ms segments
of the stimuli in Single condition were used. The purpose
was to examine MMF characteristics elicited by different
portions of acoustic difference in /l-r/.
4. Truncated 100ms condition. The middle 100ms of F3
transition of the Single condition stimuli were used.
Stimuli were monaurally delivered to the right ear via a plastic
tube at 80 dB SPL. Deviant occurrence was at 0.15 probability
with at least two intervening standards. Interstimulus intervals
were randomized between 800 and 1200 ms. There were two
blocks of stimuli with the standard and the deviant reversed in
the second block. A ten-minute break was inserted between the
two blocks in one experiment to reduce effects of habituation
and fatigue. After the break, head positioning data were fitted
again on four coils pasted on the scalp with 98% accuracy or
above. Head origin deviations were adjusted in the range of
0~3.0 mm before proceeding to the second block.
The MEG data were collected using the Neuromag 122-channel
whole-head SQUID gradiometer housed in a four-layered
magnetically shielded room at NTT Communications Science
Laboratories in Japan. The analog filter was 0.01~100 Hz, and
the sampling frequency was 497 Hz. Epochs with MEG 3000
fT/cm or EOG 150 µV indicative of artefacts were rejected
online. At least 100 epochs were averaged for the deviant and
the standard immediately before the deviant. The data were
digitally filtered at 0.8 ~ 40 Hz offline. The analysis time was -
100 ~ 800 ms. For each experiment, N1m was determined at
post-stimulus 80~160 ms using a subset of 44 channels from
both hemispheres. The MMF peak was determined from
subtracted waves using a time window of 200 ms after N1m.
3. Results
3.1 Behavioral Identification Functions
Figure 2 shows the group average identification functions for
Japanese and American subjects. Overall, Japanese listeners
were more biased in labeling more stimuli as /ra/.
Nonparametric two-tailed Kolmogorov-Smirnov tests on the
percent-correct identification indicated significant difference
between the two groups of subjects on every stimulus on the
continuum except No.5 (p < .01).
0%
20%
40%
60%
80%
100%
1234567891011
/ra-la/ Stimulus Continuum
Percent identified as
/ra/
Japanese
American
Figure 2. Average identification functions for 10 Japanese and
10 American subjects.
3.2 Behavioral Pretest and Posttest
Table 1 summarizes the pretest and posttest data for 320
identification trials. On average, training resulted in
improvement of correct identification from 57% to 79%.
Binomial tests indicated that before training above chance level
performance was observed only in the subcategory of Talker 2,
and after training performance in correct identification became
significant for all sub-categories. Training effects were found to
be transferable to the novel untrained stimuli at a sizable
improvement of 26.7%.
(a)
Syllabic context CV VCV
Pre .53 .60
Post .79 .78
(b)
Vowel context /i/ /e/ /a/ /o/ /u/
Pre .55 .59 .55 .56 .58
Post .83 .89 .73 .73 .75
(c)
Talker 1 2 3 4 5 6 7 8
Pre .55 .75 .50 .55 .48 .55 .63 .53
Post .83 .70 .88 .73 .68 .88 .75 .88
Table 1. Pre- and post- test correct identifications according to
(a) syllabic contexts, (b) vowel contexts, and (c) talkers.
Numbers in bold face were for stimuli not used in training.
Comparable training effects were observed for all stimuli in the
/ra-la/ continuum except No. 1 and No. 4 (Figure 3). However,
the post-training Japanese subject’s phonetic boundary for /ra-
la/ (between stimuli No. 8 and No. 9) shifted towards /la/ from
the American subjects’ boundary location (between No. 5 and
No. 6) by three steps of the equalized acoustic change in the
continuum.
0%
20%
40%
60%
80%
100%
1234567891011
/ra-la/ Stimulus Continuum
Percent identified as
/ra/
Pre
Post
Figure 3. Pretest and Posttest identification functions.
3.2 Neuromagnetic data
Tables 2 & 3 show pretest and posttest mismatch field results
for all four MEG conditions. Compared to the noise level in
baseline, the MMF values were significant. For the speech
stimuli, training results in enhanced MMF peak responses in the
left hemisphere (163.0~269.6 ms) coupled with reduced
activities in the right hemisphere (169.1~295.8 ms). Figures 4 &
5 illustrate this pretest and posttest change in waveforms and
MMF dipole localization. This pattern of neural plasticity was
not observed for truncated stimuli, which the subject perceived
as non-speech sounds. Prior to training, the right hemisphere
appeared to be heavily involved in detecting the acoustic
differences in stimuli for all four conditions. After training,
MMF data exhibited left-hemisphere dominance in the Single
condition, bilaterally equalized cortical involvement in the
Multiple condition, and bilaterally increased mismatch activity
for truncated stimuli with one exception in the 155ms condition.
Single Multiple
Left Right Left Right
MMF
(fT/cm) la-ra ra-la la-ra ra-la la-ra ra-la la-ra ra-la
Pre 22.35 23.60 28.91 27.78 21.22 23.23 31.00 27.73
Post 30.29 30.57 23.61 Null 23.51 24.28 23.22 24.29
Table 2. Pre- and post- test MMF peak magnitude in Single and
Multiple conditions. “la-ra” indicates subtraction of deviant /la/
from standard /ra/. Vice versa for “ra-la”.
155ms 100ms
Left Right Left Right
MMF
(fT/cm) s1-s2 s2-s1 s1-s2 s2-s1 s3-s4 s4-s3 s3-s4 s4-s3
Pre 19.50 Null 32.52 27.98 16.93 22.30 28.06 23.72
Post 25.10 24.24 28.94 37.20 21.88 26.28 36.83 25.35
Table 3. Pre- and post- test MMF peak magnitude in 155ms and
100ms conditions. “s1” and “s2” indicate the 155ms portions
from /la/ and /ra/. “s3” and “s4” are for the 100ms portions.
Figure 4. Waveforms of two individual channels respectively
from the left and right hemispheres in the Single condition. The
upper panel is for pretest and lower panel for posttest. The solid
wave is for standard and dotted wave for deviant. MEG scales:
vertical = 100 fT/cm, horizontal = 200 ms.
Figure 5. Dipole source localization for MMFs corresponding
to the waveforms in Figure 4.
4. Discussion
The success of the behavioral training program is evidenced by
substantial improvement in // and /l/ identification of the
Japanese listener, and this ability was transferable to untrained
stimuli. However, the Japanese subject’s enhanced sensitivity
to the crucial F3 transition appeared to be driven by the
transitional direction and the initial steady F3 frequency locale
in relation to F2. Among the 11 synthetic syllables in the
continuum, No. 1-8 have a rising F3 transition and No. 9-11 a
falling F3 transition. We speculate that the Japanese subjects
including the trained subject primarily used rising F3 transition
as an acoustic cue for /ra/. The fact that Americans treated No. 7
and 8 with shallow rising F3 as /la/ could be due to the
perceptual magnet effect that the prototype /la/ assimilates its
neighboring stimuli into the category [19]. In this perspective,
the /ra/ prototype in Japanese could interfere with the training
process as a limit on plasticity. Work in our laboratory showed
that unlike the Americans Japanese listeners tend to separate /l/
and /r/ stimuli acoustically on the F2 dimension. This factor
could also interfere with the subject’s performance, especially
when the initial portion of F3 in the consonant is very close to
F2 as in Stimuli No. 1 and No. 2.
Neural plasticity in the Japanese subject was found to show a
right-to-left hemispheric shift of cortical MMF activities in the
establishment of linguistic /l/ and /r/ categories. Earlier we
reported that an American control’s MMFs showed a left
hemisphere dominance for /l/ and /r/ whereas the Japanese
subjects showed bilateral involvement [20]. Training appeared
to lead to more linguistic analysis of the speech stimuli in the
left hemisphere. The patterns in pre-attentive MMF activation
underlying stimulus discriminability and categorization
confirmed that the MMF is a sensitive measure of neural
activities in acoustic and phonetic processing.
Little is known about how linguistic experience causes people to
attend to different dimensions of the stimuli and how language
training could be designed to accurately map linguistic
representations for nonnative speech contrasts. It is reported that
even early and extensive exposure to a second language is not
sufficient to attain the ultimate phonological competence of
native speakers [21]. The formation of a new phonetic category
in mental representation as well as its influence on speech
perception in terms of behavioral and neurophysiologic
measures merits further empirical work.
Acknowledgements
This work has been supported by NIH (HD 37954) and Human
Frontiers Science Program (HFSP 159) to Dr. Patricia K. Kuhl
and by NTT traineeship to Yang Zhang. MRI facilities were
provided by Tokyo Denki University. The authors would like to
thank Dr. Yoh'ichi Tohkura for his support for this project.
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Neural plasticity in speech acquisition and learning is concerned with the timeline trajectory and the mechanisms of experience-driven changes in the neural circuits that support or disrupt linguistic function. In this selective review, we discuss the role of phonetic learning in language acquisition, the "critical period" of learning, the agents of neural plasticity, and the distinctiveness of linguistic systems in the brain. In particular, we argue for the necessity to look at brain - behavior connections using modern brain imaging techniques, seek explanations based on measures of neural sensitivity, neural efficiency, neural specificity and neural connectivity at the cortical level, and point out some key factors that may facilitate or limit seco nd language learning. We conclude by highlighting the theoretical and practical issues for future studies and suggest ways to optimize language learning and treatment.
... In the phonetic domain, there is clear evidence that early language learning does not involve a permanent loss of perceptual sensitivity to all the nonnative distinctions (Best et al., 2001;Werker and Tees, 2005). Furthermore, adults' perception of nonnative speech can be improved by using a variety of short-term intensive training methods (Akahane-Yamada et al., 1997;Bradlow et al., 1999;Hazan et al., 2006;Iverson et al., 2005;Jamieson and Morosan, 1986;Logan et al., 1991;McCandliss et al., 2002;Pruitt et al., 2006;Strange and Dittmann, 1984;Tremblay et al., 1997;Wang et al., 2003;Zhang et al., 2000). These training studies, among others, have not only provided important empirical data for reevaluating the "critical period" hypothesis but also revealed key factors that facilitate second language learning independent of age. ...
... To address the underlying mechanisms of brain plasticity for phonetic learning in adulthood, we designed a training software program in a preliminary single-subject MEG study to test its success (Zhang et al., 2000). The program incorporated features that were motivated by studies of infant-directed speech (IDS) or "motherese" (Burnham et al., 2002;Fernald and Kuhl, 1987;Kuhl et al., 1997;Liu et al., 2003), including adaptive signal enhancement, visible articulation cues, a large stimulus set with high variability, and self-initiated selection. ...
... There are two main objectives in the present training study: (a) to test the efficacy of our IDSmotivated training program in adults' learning of second language phonetic categories, and (b) to examine two hypothetical neural markers of learning in terms of brain-behavior correlates: neural sensitivity, as measured by the mismatch field response for phonetic discrimination (Näätänen et al., 1997), and neural efficiency, as measured by the focal degree and duration of brain activation during phonetic perception in terms of equivalent current dipole (ECD) clusters (Zhang et al., 2005). Previous neurophysiological studies have shown strong evidence of learning-induced enhancement in neural sensitivity to support phonetic categorization in adults as well as in children (Cheour et al., 1998;Imaizumi et al., 1999;Kraus et al., 1995;Menning et al., 2002;Näätänen et al., 1997;Nenonen et al., 2005;Rivera-Gaxiola et al., 2000;Tremblay et al., 1997;Winkler, 1999;Zhang et al., 2000). There is also evidence for learning-induced shift toward left hemisphere dominance in terms of enhanced neural sensitivity for linguistic processing (See Näätänen et al., 2007 for a review.). ...
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The present study used magnetoencephalography (MEG) to examine perceptual learning of American English /r/ and /l/ categories by Japanese adults who had limited English exposure. A training software program was developed based on the principles of infant phonetic learning, featuring systematic acoustic exaggeration, multi-talker variability, visible articulation, and adaptive listening. The program was designed to help Japanese listeners utilize an acoustic dimension relevant for phonemic categorization of /r-l/ in English. Although training did not produce native-like phonetic boundary along the /r-l/ synthetic continuum in the second language learners, success was seen in highly significant identification improvement over twelve training sessions and transfer of learning to novel stimuli. Consistent with behavioral results, pre-post MEG measures showed not only enhanced neural sensitivity to the /r-l/ distinction in the left-hemisphere mismatch field (MMF) response but also bilateral decreases in equivalent current dipole (ECD) cluster and duration measures for stimulus coding in the inferior parietal region. The learning-induced increases in neural sensitivity and efficiency were also found in distributed source analysis using Minimum Current Estimates (MCE). Furthermore, the pre-post changes exhibited significant brain-behavior correlations between speech discrimination scores and MMF amplitudes as well as between the behavioral scores and ECD measures of neural efficiency. Together, the data provide corroborating evidence that substantial neural plasticity for second-language learning in adulthood can be induced with adaptive and enriched linguistic exposure. Like the MMF, the ECD cluster and duration measures are sensitive neural markers of phonetic learning.
... Although earlier studies showed the efficacy of HVPT only with the identification training protocol, a recent study demonstrated the feasibility of both identification and discrimination training with similar improvements (Shinohara and Iverson, 2018). Some studies further indicated the benefits of combining systematic temporal/spectral exaggeration with adaptive training in the HVPT paradigm (Zhang et al., 2000(Zhang et al., , 2009Grenon et al., 2019) while achieving limited success in overcoming the native language interference. But the effects of this modified and integrated HVPT approach have not been directly compared with those without introducing the temporal acoustic exaggeration. ...
... For instance, exaggerations in pitch range and contour do not necessarily facilitate phonetic categorization (Trainor and Desjardins, 2002;Kitamura and Burnham, 2003). Nevertheless, some studies have found that when the training input stimuli were systematically manipulated with temporal and spectral exaggeration, adult L2 perceptual learning could be greatly enhanced (Zhang et al., 2000(Zhang et al., , 2009Iverson et al., 2005). The critical notion here is that by exaggerating acoustic differences between stimuli, researchers can make the contrast more discriminable, which can be incorporated in a scaffolding structure for step-by-step adaptive training based on the individual learners' perceptual ability to facilitate phonetic training (Zhang and Cheng, 2011). ...
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High variability phonetic training (HVPT) has been found to be effective in helping adult learners acquire nonnative phonetic contrasts. The present study investigated the role of temporal acoustic exaggeration by comparing the canonical HVPT paradigm without involving acoustic exaggeration with a modified adaptive HVPT paradigm that integrated key temporal exaggerations in infant-directed speech (IDS). Sixty native Chinese adults participated in the training of the English /i/ and /ɪ/ vowel contrast and were randomly assigned to three subject groups. Twenty were trained with the typical HVPT (the HVPT group), twenty were trained under the modified adaptive approach with acoustic exaggeration (the HVPT-E group), and twenty were in the control group. Behavioral tasks for the pre- and post- tests used natural word identification, synthetic stimuli identification, and synthetic stimuli discrimination. Mismatch negativity (MMN) responses from the HVPT-E group were also obtained to assess the training effects in within- and across-category discrimination without requiring focused attention. Like previous studies, significant generalization effects to new talkers were found in both the HVPT group and the HVPT-E group. The HVPT-E group, by contrast, showed greater improvement as reflected in larger progress in natural word identification performance. Furthermore, the HVPT-E group exhibited more native-like categorical perception based on spectral cues after training, together with corresponding training-induced changes in the MMN responses to within- and across- category differences. These data provide the initial evidence supporting the important role of temporal acoustic exaggeration with adaptive training in facilitating phonetic learning and promoting brain plasticity at the perceptual and pre-attentive neural levels.
... (b) The effects of NLNC are self-reinforcing and bidirectional -it enhances efficient processing of compatible higher-order linguistic patterns, while at the same time hindering the detection of non-conforming patterns contained in foreign languages, as shown behaviorally (e.g., Iverson et al., 2003) and neurally at the pre-attentive level (e.g., Zhang et al., 2005). (c) Neural commitment is subject to continual shaping and reshaping by experience -Enriched exposure (including high stimulus variability and talker variability, exaggerated speech, and audiovisual training) not only provides enhanced stimulation to the infant brain (e.g., but also can induce substantial plasticity in the adult brain for second language learning, producing hemispheric reallocation of resources for enhanced phonetic sensitivity and more efficient linguistic processing (Zhang et al., 2000. (d) Neural commitment involves the binding of perception and action systems to facilitate speech communication, and this process depends on social/affective learning early in life (Imada et al., 2006;Kuhl, 2007;Stevens and Zhang, 2014). ...
... The perception data were collected from both subject groups with a revised Speech Assessment and Training software program (SAT) based on versions used in previous publications (Zhang et al., 2000;Cheng andZhang, 2009, 2013;Zhang and Cheng, 2011). In the current implementation, isolated word stimuli were used, containing all consonants with Standard American English pronunciation (see Table 1 for examples and the target phonemes). ...
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The present study investigated how syllable structure differences between the first Language (L1) and the second language (L2) affect L2 consonant perception and production at syllable-initial and syllable-final positions. The participants were Mandarin-speaking college students who studied English as a second language. Monosyllabic English words were used in the perception test. Production was recorded from each Chinese subject and rated for accentedness by two native speakers of English. Consistent with previous studies, significant positional asymmetry effects were found across speech sound categories in terms of voicing, places of articulation, and manner of articulation. Furthermore, significant correlations between perception and accentedness ratings were found at the syllable onset position but not for the coda. Many exceptions were also found, which could not be solely accounted for by differences in L1-L2 syllabic structures. The results show a strong effect of language experience at the syllable level, which joins force with acoustic, phonetic, and phonemic properties of individual consonants in influencing positional asymmetry in both domains of L2 segmental perception and production. The complexities and exceptions call for further systematic studies on the interactions between syllable structure universals and native-language interference and refined theoretical models to specify the links between perception and production in second language acquisition. (Open Access Web Link at: http://journal.frontiersin.org/article/10.3389/fpsyg.2015.01801/full)
... Studi di tipo neurofisiologico hanno testato gli effetti di training mirati (10-12 giorni per 1,5 ore al giorno) nella riorganizzazione della corteccia uditiva in apprendenti adulti giapponesi dell'inglese L2 (Zhang et al., 2000), tedeschi dell'inglese L2 (Menning et al., 2002) e finlandesi dell'inglese L2 (Ylinen et al., 2009). Questi lavori dimostrano che il sistema percettivo di un adulto non perde di plasticità e che la sua riattivazione gli consente di acquisire nuove categorie fonetico-fonologiche. ...
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Fonetica e fonologia della L2 in classe: problematiche e prospettive didattiche dal versante delle neuroscienze cognitive (e oltre) Questo contributo vuole stimolare la riflessione in merito alla didattica della fonetica e della fonologia nell'insegnamento della L2. È paradossale che un bambino acceda alla grammatica della lingua nativa partendo dal livello fonetico-fonologico, mentre lo studio in classe di una L2 pretenda di partire dai livelli lessicale e morfo-sintattico. Questa pratica deriva dall'idea estrema di un periodo critico oltre il quale l'apprendimento in modo naturale di un sistema linguistico è impedito. In realtà, l'impedimento a raggiungere abilità in percezione e produzione dei suoni L2 dipende dalla quantità e qualità degli stimoli ricevuti in classe. Lo dimostrano una serie di studi comportamentali e neurofisiologici. Altri studi neurofisiologici e di fonetica articolatoria dimostrano anche come un addestramento mirato può riattivare capacità uditive e articolatorie sopite. Sulla base dei software multimediali a disposizione, la parte finale del contributo propone spunti di riflessione per una didattica da implementare in classe. Breve abstract di circa 130 parole, che non deve essere preceduto dall'intestazione di paragrafo. Parole chiave: parola1, parola 2, parola 3, parola4, parola5. 1. Introduzione La pubblicità online straripa di corsi e metodi che promettono di rivelarci i segreti ultimi per apprendere le lingue. Esagerando, ma non troppo, se c'è un segreto per diventare poliglotti è quello di ritornare bambini. A poche settimane dalla nascita un bambino è in grado di discriminare tutti i suoni delle lingue naturali. A partire però dai 12
... An adaptive version of HVPT was developed for the current study, with the aim of helping Japanese listeners decrease their sensitivity to vowel duration while increasing their sensitivity to changes in formant frequencies by building on previous studies that showed that adaptive versions of HVPT are successful in improving L2 learners' perception of the targeted L2 contrast (e.g., Ingvalson et al., 2012;McCandliss, Fiez, Protopapas, Conway, & McClelland, 2002;Protopapas & Calhoun, 2000;Zhang et al., 2000Zhang et al., , 2009. The training paradigm generally progressed from easy to hard by gradually integrating changes in speaking rate (slow, normal, fast) and stimulus complexity (CVC and complex minimal pairs, nearminimal pairs, sentences), and by varying how the stimuli from different talkers were presented (one talker at a time or mixed). ...
Article
Native Japanese speakers often perceive English vowels based on their duration, whereas native speakers use spectral cues (formant frequencies). The current study examined whether 23 Japanese adult learners of English could create a new vowel category along the spectral dimension after phonetic training with the English vowels /i/-/ɪ/ as in beat and bit. As in previous training studies, the Japanese trainees improved their ability to categorize the vowels in tokens included in the training, and were able to generalize to novel tokens and talkers. A cue-weighting task confirmed that the Japanese trainees categorized the vowels based on temporal cues before training , presumably because vowel duration is used phonologically in Japanese. While 12 of the Japanese trainees still relied on vowel duration to distinguish the English vowels after training, 11 of them successfully created a new vowel category along the spectral dimension. However, their category boundary between /i/-/ɪ/ was set at a different location from that of native speakers. We interpret these results as providing evidence that it is possible for late inexperienced learners to create new phonetic categories with phonetic training, but that the new categories may be subject to phonetic category dissimilation, an effect previously documented with early bilinguals.
... However, other studies indicate that phonetic expertise does not promote perceptual flexibility; therefore, perception of novel speech is not enhanced by previous phonetic experience (Pallier, Bosch, & Sebastian-Galles, 1997;Werker, 1986). It appears that bilinguals can only improve the perception of second language sounds when training with the same second language phonemes subjects are already learning outside the laboratory; as in the case of Japanese-English second language learners receiving phonetic training to differentiate English /l/ and /r/ (Zhang et al., 2000). Therefore, it has to be noted that some of the studies cited above may only test novel aspects of existing speech contrasts (such as duration as in the case of geminates or voice onset time) rather than truly novel speech sounds. ...
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Aims: The goal of this study was to investigate if phonetic experience with two languages facilitated the learning of novel speech sounds or if general perceptual abilities independent of bilingualism played a role in this learning. Method: The underlying neural mechanisms involved in novel speech sound learning were observed in groups of English monolinguals (n = 20), early Spanish–English bilinguals (n = 24), and experimentally derived subgroups of individuals with advanced ability to learn novel speech sound contrasts (ALs, n = 28) and individuals with non-advanced ability to learn novel speech sound contrasts (non-ALs, n = 16). Subjects participated in four consecutive sessions of phonetic training in which they listened to novel speech sounds embedded in Hungarian pseudowords. Participants completed two fMRI sessions, one before training and another one after training. While in the scanner, participants passively listened to the speech stimuli presented during training. A repeated measures behavioral analysis and ANOVA for fMRI data were conducted to investigate learning after training. Results and conclusions: The results showed that bilinguals did not significantly differ from monolinguals in the learning of novel sounds behaviorally. Instead, the behavioral results revealed that regardless of language group (monolingual or bilingual), ALs were better at discriminating pseudowords throughout the training than non-ALs. Neurally, region of interest (ROI) analysis showed increased activity in the superior temporal gyrus (STG) bilaterally in ALs relative to non-ALs after training. Bilinguals also showed greater STG activity than monolinguals. Extracted values from ROIs entered into a 2×2 MANOVA showed a main effect of performance, demonstrating that individual ability exerts a significant effect on learning novel speech sounds. In fact, advanced ability to learn novel speech sound contrasts appears to play a more significant role in speech sound learning than experience with two phonological systems.
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At the forefront of research on language are new data demonstrat- ing infants' strategies in the early acquisition of language. The data show that infants perceptually "map" critical aspects of ambient language in the first year of life before they can speak. Statistical and abstract properties of speech are picked up through exposure to ambient language. Moreover, linguistic ex- perience alters infants' perception of speech, warping perception in a way that enhances native-language speech processing. Infants' strategies are unexpect- ed and unpredicted by historical views. At the same time, research in three ad- ditional disciplines is contributing to our understanding of language and its acquisition by children. Cultural anthropologists are demonstrating the uni- versality of adult speech behavior when addressing infants and children across cultures, and this is creating a new view of the role adult speakers play in bring- ing about language in the child. Neuroscientists, using the techniques of mod- ern brain imaging, are revealing the temporal and structural aspects of language processing by the brain and suggesting new views of the critical peri- od for language. Computer scientists, modeling the computational aspects of childrens' language acquisition, are meeting success using biologically inspired neural networks. Although a consilient view cannot yet be offered, the cross- disciplinary interaction now seen among scientists pursuing one of humans' greatest achievements, language, is quite promising.
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At the forefront of research on language are new data demonstrating infants' strategies in the early acquisition of language. The data show that infants perceptually “map” critical aspects of ambient language in the first year of life before they can speak. Statistical and abstract properties of speech are picked up through exposure to ambient language. Moreover, linguistic experience alters infants' perception of speech, warping perception in a way that enhances native-language speech processing. Infants' strategies are unexpected and unpredicted by historical views. At the same time, research in three additional disciplines is contributing to our understanding of language and its acquisition by children. Cultural anthropologists are demonstrating the universality of adult speech behavior when addressing infants and children across cultures, and this is creating a new view of the role adult speakers play in bringing about language in the child. Neuroscientists, using the techniques of modern brain imaging, are revealing the temporal and structural aspects of language processing by the brain and suggesting new views of the critical period for language. Computer scientists, modeling the computational aspects of childrens' language acquisition, are meeting success using biologically inspired neural networks. Although a consilient view cannot yet be offered, the cross-disciplinary interaction now seen among scientists pursuing one of humans' greatest achievements, language, is quite promising.
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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.
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Linguistic experience affects phonetic perception. However, the critical period during which experience affects perception and the mechanism responsible for these effects are unknown. This study of 6-month-old infants from two countries, the United States and Sweden, shows that exposure to a specific language in the first half year of life alters infants' phonetic perception.
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Previous work in which we compared English infants, English adults, and Hindi adults on their ability to discriminate two pairs of Hindi (non-English) speech contrasts has indicated that infants discriminate speech sounds according to phonetic category without prior specific language experience (Werker, Gilbert, Humphrey, & Tees, 1981), whereas adults and children as young as age 4 (Werker & Tees, in press), may lose this ability as a function of age and or linguistic experience. The present work was designed to (a) determine the generalizability of such a decline by comparing adult English, adult Salish, and English infant subjects on their perception of a new non-English (Salish) speech contrast, and (b) delineate the time course of the developmental decline in this ability. The results of these experiments replicate our original findings by showing that infants can discriminate non-native speech contrasts without relevant experience, and that there is a decline in this ability during ontogeny. Furthermore, data from both cross-sectional and longitudinal studies shows that this decline occurs within the first year of life, and that it is a function of specific language experience. © 2002 Published by Elsevier Science Inc.
Article
Listening to language during the first year of life has a dramatic effect on infants’ perception of speech. With increasing exposure to a particular language, infants begin to ignore phonetic variations that are irrelevant in their native language. To examine these effects, 72 American and Japanese infants were tested at two ages, 6–8 months and 10–12 months, with synthetic versions of the American English /r/ and /l/ consonants. The /r–l/ contrast is not phonemic in Japanese. In both countries, the same experimenters, technique (head‐turn conditioning), and stimuli were used. The results revealed two significant effects. The first shows the impact of language experience on speech perception. At 6–8 months of age, American and Japanese infants did not differ. Both groups performed significantly above chance (American M=63.7%; Japanese M=64.7%). By 10–12 months of age, American infants demonstrated significant improvement relative to performance at 6–8 months (M=73.8%), while Japanese infants declined (M=59.9%). Second, performance varied significantly as a function of the direction of stimulus change (/l/ to /r/ easier than the reverse), regardless of age or language experience. Discussion will focus on separating effects attributable to linguistic and psychoacoustic factors. [Work supported by NIH.]
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Previous research has shown that English speakers have great difficulty distinguishing the dental and retroflex stop‐consonants of the Hindi language. However, native Japanese speakers have somewhat less difficulty perceiving this contrast even though it is not employed in the Japanese language. Best and colleagues have attributed similar differences in the perception of non‐native speech sounds to differences in the assimilation of such sounds to native‐language speech categories [Best, McRoberts, and Sithole, J. Exp. Psych: Human Percept. Perform. 14 (1988)]. According to Best’s Perceptual Assimilation Model (PAM), four patterns of assimilation have been described which are purportedly predictive of perceptual difficulty. To determine if this model could be applied to the present case, native speakers of English and Japanese transcribed multiple instances of the Hindi consonants in different voicing/manner classes, produced with different vowels. Marked differences were found between the responses of the two language groups which were partially dependent upon the voicing/manner class of the contrast. Interestingly, an assimilation pattern emerged which was different from those discussed in PAM. Implications of these findings for PAM and for perceptual training of non‐native speech sounds will be discussed. [Work supported in part by NIDCD.]
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Previous work in which we compared English infants, English adults, and Hindi adults on their ability to discriminate two pairs of Hindi (non-English) speech contrasts has indicated that infants discriminate speech sounds according to phonetic category without prior specific language experience (Werker, Gilbert, Humphrey, & Tees, 1981), whereas adults and children as young as age 4 (Werker & Tees, in press), may lose this ability as a function of age and or linguistic experience. The present work was designed to (a) determine the generalizability of such a decline by comparing adult English, adult Salish, and English infant subjects on their perception of a new non-English (Salish) speech contrast, and (b) delineate the time course of the developmental decline in this ability. The results of these experiments replicate our original findings by showing that infants can discriminate non-native speech contrasts without relevant experience, and that there is a decline in this ability during ontogeny. Furthermore, data from both cross-sectional and longitudinal studies shows that this decline occurs within the first year of life, and that it is a function of specific language experience.
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Historically, auditory research has focused predominately upon how relatively simple acoustic signals are represented in the neuronal responses of the auditory periphery. However, in order to understand the neurophysiology underlying speech perception, the ultimate objective is to discover how speech sounds are represented in the central auditory system and to relate that representation to the perception of speech as a meaningful acoustic signal. This paper reviews three areas that pertain to the central auditory representation of speech: (1) the differences in neural representation of speech sounds at different levels of the auditory system; (2) the relation between the representation of sound in the auditory pathway and the perception/misperception of speech, and (3) the training-related plasticity of speech sound neural representation and speech perception.
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Discriminiationi of synthetic speech sounds was studied in 1- and 4-month-old infants. The speech sounds varied along an acoustic dimension previously shown to cue phonemic distinctions among the voiced and voiceless stop consonants in adults. Discriminability was measured by an increase in conditioned response rate to a second speech sound after habituation to the first speech sound. Recovery from habituation was greater for a given acoustic difference when the two stimuli were from different adult phonemic categories than when they were from the same category. The discontinuity in discrimination at the region of the adult phonemic boundary was taken as evidence for categorical perception.