Paul Iverson's research while affiliated with University College London and other places

Publications (115)

Article
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Japanese adults and Spanish-Catalan children received auditory phonetic training for English vowels using a novel paradigm, a version of the common children's card game Concentration. Individuals played a computer-based game in which they turned over pairs of cards to match spoken words, drawn from sets of vowel minimal pairs. The training was effe...
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Younger learners are better at acquiring second-language (L2) phoneme contrasts than are older learners, but this general correlation between age and learning ability is often confounded with factors such as how late learners use their L2 in daily life. The present study trained Japanese speakers across a wide age range (young children through adul...
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The present study investigated how single-talker and babble maskers affect auditory and lexical processing during native (L1) and non-native (L2) speech recognition. Electroencephalogram (EEG) recordings were made while L1 and L2 (Korean) English speakers listened to sentences in the presence of single-talker and babble maskers that were colocated...
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This study measured infants’ neural responses for spectral changes between all pairs of a set of English vowels. In contrast to previous methods that only allow for the assessment of a few phonetic contrasts, we present a new method that allows us to assess changes in spectral sensitivity across the entire vowel space and create two-dimensional per...
Article
Purpose The intelligibility of an accent strongly depends on the specific talker–listener pairing. To explore the causes of this phenomenon, we investigated the relationship between acoustic–phonetic similarity and accent intelligibility across native (1st language) and nonnative (2nd language) talker–listener pairings. We also used online measures...
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Research into non-native (L2) speech perception has increased the need for specialized experimental materials. The Non-Native Speech Recognition (NNSR) sentences are a new large-scale set of speech recognition materials for research with L2 speakers of English at CEFR level B1 (North, Ortega, & Sheehan, 2010) and above. The set comprises 439 triple...
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Dyslexia is characterized by poor reading skills, yet often also difficulties in second-language learning. The differences between native- and second-language speech processing and the establishment of new brain representations for spoken second language in dyslexia are not, however, well understood. We used recordings of the mismatch negativity co...
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Speech communication in a non-native language (L2) can feel effortful, and the present study suggests that this effort affects both auditory and lexical processing. EEG recordings (electroencephalography) were made from native English (L1) and Korean listeners while they listened to English sentences spoken with two accents (English and Korean) in...
Conference Paper
Previous research has suggested that cortical entrainment to slow amplitude fluctuations in the speech signal (i.e., amplitude envelope) plays an important role in speech perception. However, it remains unclear how cortical entrainment to the speech envelope relates to higher-level linguistic processes. The present study investigated how cortical e...
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This study explored the relationship between signal degradation and electrophysiological measures of speech processing, in order to understand how these measures relate to intelligibility and listening effort. Subjects heard two talkers presented to different ears, with the target talker presented in quiet, three levels of speech-shaped noise ( + 3...
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Second-language (L2) learners can benefit from exposure to phonetically variable speech during computer-based training. Moreover, this training can be effective even for L2 learners who have extensive exposure to their L2 in daily life, suggesting that there is something specific about the training task that aids learning. The present study compare...
Conference Paper
Recent studies have shown that accurate vowel category perception can be maintained at fundamental frequencies (fo) up to at least 880 Hz. In such cases, the typical first formant frequency (F1) of most vowels is exceeded by f o and the vocal tract transfer function is to a high degree undersampled. It seems, therefore, unlikely that common formant...
Conference Paper
Brain oscillations in the auditory cortex become entrained to slow amplitude fluctuations in the speech signal (i.e., amplitude envelope) during speech comprehension. Previous research has suggested that this cortical activity plays an important role in speech perception by aligning neuronal excitability to parts of the incoming speech signal that...
Conference Paper
Listening effort modulates auditory processing for speech, such that attention to a target talker in the presence of a distractor increases the entrainment of cortical activity to the target speech amplitude envelope. Similarly, lexical-processing effort can be measured in EEG recordings, with more extensive lexical search being measured as a more...
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Native Japanese speakers can have difficulty learning the English /r/-/l/ distinction, and they likewise are poorer than native English speakers at discriminating acoustic differences at the /r/-/l/ identification boundary. This study investigated the specificity of this specialization by comparing the discrimination of /r/ and /l/ under stimulus t...
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Cross-language differences in speech perception have traditionally been linked to phonological categories, but it has become increasingly clear that language experience has effects beginning at early stages of perception, which blurs the accepted distinctions between general and speech-specific processing. The present experiments explored this dist...
Article
The present study used an efficient measure of perceptual sensitivity to map perception across the British English vowel space for 80 monolingual English infants (4–5, 8–9, and 10–11 months old). Auditory evoked potentials were measured for spectral changes between concatenated vowels, which, for infants, typically evokes a positivity about 150–200...
Article
Speech recognition in noise is affected by the accents of the speakers and listeners, but it is not clear how overall accuracy is linked to the underlying perceptual and lexical processes. The present study investigated speech recognition for two native-accent groups (Southern British English and Glaswegian) and one non-native group (Spanish learne...
Conference Paper
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Previous research has found that listeners understand talkers who speak with the same accent as themselves better than others. The aim of the current study was to investigate how speech intelligibility is modulated by this talker-listener accent interaction when native and non-native listeners hear spontaneous speech. To this end, native Southern B...
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Abstract Memory for speech sounds is a key component of models of verbal working memory (WM). But how good is verbal WM? Most investigations assess this using binary report measures to derive a fixed number of items that can be stored. However, recent findings in visual WM have challenged such 'quantized' views by employing measures of recall preci...
Conference Paper
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This study examined cross-dialectal differences on the perception of Greek vowels. Speakers of Standard Modern Greek (SMG) and two dialectal areas (Crete, Kozani), all with five vowels in their systems, chose best exemplar locations (prototypes) for Greek vowels embedded in a carrier sentence spoken by a speaker of their dialect. The results showed...
Article
The present study examined epenthetic vowels produced by Korean learners of English in read sentences, in terms of acoustic measures and extra-phonological factors. The results demonstrated three main findings. First, epenthetic vowels had relatively high F1 values and a wide range of F2 values. Most of the epenthetic vowels were inserted near Kore...
Article
Korean L2 speakers have many problems learning the pronunciation of English words. One of these problems is vowel epenthesis. Vowel epenthesis is the insertion of vowels into or between words, and Korean learners of English typically do this between successive consonants, either within clusters, or across syllables, word boundaries or following fin...
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Research on mammals predicts that the anterior striatum is a central component of human motor learning. However, as vocalizations in most mammals are innate, much of the neurobiology of human vocal learning has been inferred from studies on songbirds. Essential for song learning is a pathway, the homologue of mammalian cortical-basal ganglia 'loops...
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Modern neuroimaging techniques have advanced our understanding of the distributed anatomy of speech production, beyond that inferred from clinico-pathological correlations. However, much remains unknown about functional interactions between anatomically distinct components of this speech production network. One reason for this is the need to separa...
Article
Previous work has suggested that the recognition of speech in noise is affected by the accent similarity of the speaker and listener, as well as by the familiarity of the speaker's accent. The present study investigated this further by constructing multidimensional accent maps for British English speakers, as well as a small group of general Americ...
Article
The acoustic change complex (ACC) is a P1-N1-P2 onset response to changes between sounds measured using EEG, which when measured at a central location, is not thought to be affected by the language experience of the listener. Recent research has shown that with a pair of stimuli, there is an asymmetry between the ACC recorded when they are presente...
Article
The intelligibility of accented speech in noise greatly depends on the pairing of speaker and listener, where two important factors are a listener's familiarity with a speaker's accent and the acoustic similarity between their accents. In this study, we present patterns of the intelligibility of standard British English, Glaswegian English and Span...
Article
The aim of this study was to examine how auditory vowel processing by native (L1) and non-native (L2) speakers is reflected in their neuronal source architecture and in coupling between brain regions. We used the magnetic Mismatch Response/MMNm to test automatic brain responses to within- and between-category vowels with English controls and Englis...
Article
Previous work has shown that both the speed and accuracy of word recognition can be reduced if a talker has a regional or non-native accent, particularly under noisy conditions. This study investigated whether the reduced intelligibility of some accents in noise are related to aspects of speech processing in quiet. Our goal was to see if difficulti...
Conference Paper
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Computer-based perceptual training has proven successful for improving English /r/-/l/ perception by Japanese adults, but this has not been tested with younger age groups, who presumably have greater perceptual plasticity. The present study examined phonetic training for children 6-8 years old. The training program included identification and discr...
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In this study, we used magnetoencephalography and a mismatch paradigm to investigate speech processing in stroke patients with auditory comprehension deficits and age-matched control subjects. We probed connectivity within and between the two temporal lobes in response to phonemic (different word) and acoustic (same word) oddballs using dynamic cau...
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This study trained 36 Korean L2 speakers on vowel identification and prosody recognition (focus and lexical stress), with the aim of investigating the extent to which training improves general speech perception abilities or specific underlying processes. Vowel training was accomplished with a high-variability identification training technique (mult...
Article
In electroencephalogram (EEG) recordings, there is a characteristic P1-N1-P2 complex after the onset of a sound, and a related complex, called the Acoustic Change Complex (ACC), when there is a change within a sound (e.g., a formant transition between two vowels). In the present study, the ACC was measured for all possible pairs of eight sustained...
Article
The finding that hyperarticulation of vowel sounds occurs in certain speech registers (e.g., infant- and foreigner-directed speech) suggests that hyperarticulation may have a didactic function in facilitating acquisition of new phonetic categories in language learners. This event-related potential study tested whether hyperarticulation of vowels el...
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The question of whether sensitivity peaks at vowel boundaries (i.e., phoneme boundary effects) and sensitivity minima near excellent category exemplars (i.e., perceptual magnet effects) stem from the same stage of perceptual processing was examined in two experiments. In Experiment 1, participants gave phoneme identification and goodness ratings fo...
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This study examined whether high-variability auditory training on natural speech can benefit experienced second-language English speakers who already are exposed to natural variability in their daily use of English. The subjects were native French speakers who had learned English in school; experienced listeners were tested in England and the less...
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This study examined the perceptual specialization for native-language speech sounds, by comparing native Hindi and English speakers in their perception of a graded set of English /w/-/v/ stimuli that varied in similarity to natural speech. The results demonstrated that language experience does not affect general auditory processes for these types o...
Article
Previous work has shown that the intelligibility of speech in noise is degraded if the speaker and listener differ in accent, in particular when there is a disparity between native (L1) and nonnative (L2) accents. This study investigated how this talker-listener interaction is modulated by L2 experience and accent similarity. L1 Southern British En...
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Native (L1) listeners are more accurate at understanding speech spoken in their own accent in noise than they are at understanding speech spoken in other L1 or non-native (L2) accents. The present study investigated whether this accent advantage is affected by perceptual adaptation. Standard Southern British English (SE) listeners were presented wi...
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This study took an individual differences approach to examine the relationship between L2 speech perception and production, with the aim of examining whether they share common underlying representations. All Japanese speakers were assessed in terms of their /r/-/l/ identification, discrimination, best exemplars, and production. The results demonstr...
Article
Individuals become specialized through development to perceive native-language speech sounds, but it is not certain whether this specialization occurs solely at the level of phonological categorization or whether pre-categorical auditory processing also becomes specialized. The present study examined this issue using 11 continua based on English ∕w...
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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 /r/. Behavioral data showed significant improvement in identifying both trained and untrained speech stimuli. Correspondingly, neuromagnetic results showed enhanced mismatch field responses i...
Article
There is a clear interaction between native and non-native accents in speech-in-noise recognition, with listeners being better at accents that match their own speech. This study investigated how this talker-listener interaction is modulated by L2 experience and accent similarity. L1 southern British English (SE) and L1 French listeners with varying...
Article
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It has been established that Korean learners of English insert epenthetic vowels within consonant clusters, likely because consonant clusters are not used in Korean. The present studies investigated whether individual differences in vowel epenthesis are more related to the perception and production of segments (vowels and consonants), prosody, or a...
Article
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Previous work has shown that accents affect speech recognition accuracy in noise, with intelligibility being modulated by the similarity between the talkers' and listeners' accents, particularly in the case where they have different L1s. The present study examined the contribution of prosody to recognizing native (L1) and non-native (L2) speech in...
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This study investigated whether individuals with small and large native-language (L1) vowel inventories learn second-language (L2) vowel systems differently, in order to better understand how L1 categories interfere with new vowel learning. Listener groups whose L1 was Spanish (5 vowels) or German (18 vowels) were given five sessions of high-variab...
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Processing of speech and nonspeech sounds occurs bilaterally within primary auditory cortex and surrounding regions of the superior temporal gyrus; however, the manner in which these regions interact during speech and nonspeech processing is not well understood. Here, we investigate the underlying neuronal architecture of the auditory system with m...
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Foreign-language learning is a prime example of a task that entails perceptual learning. The correct comprehension of foreign-language speech requires the correct recognition of speech sounds. The most difficult speech-sound contrasts for foreign-language learners often are the ones that have multiple phonetic cues, especially if the cues are weigh...
Article
Previous work has demonstrated that there is an interaction between native (L1) and non-native (L2) accents in speech recognition in noise, with listeners being better at L1 or L2 accents that match their own speech. This study investigated how L2 experience modulates this talker-listener interaction. L1 southern British English (SE) and L1 French...
Article
There are marked differences in how native speakers of Sinhala and English perceive the English w-v distinction; Sinhala speakers who have learned English as a second language are typically near chance at identification and have less than half the discrimination sensitivity of native English speakers. This poor discrimination ability is remarkable...
Article
There have been many functional imaging studies that have investigated the neural correlates of speech perception by contrasting neural responses to speech and "speech-like" but unintelligible control stimuli. A potential drawback of this approach is that intelligibility is necessarily conflated with a change in the acoustic parameters of the stimu...
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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, visibl...
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Native speakers of Japanese often have difficulty identifying English /r/ and /l/, and it has been thought that second-language (L2) learning difficulties like this are caused by how L2 phonemes are assimilated into ones native phonological system. This study took an individual difference approach to examining this relationship by testing the categ...
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The present study investigated the perception and production of English /w/ and /v/ by native speakers of Sinhala, German, and Dutch, with the aim of examining how their native language phonetic processing affected the acquisition of these phonemes. Subjects performed a battery of tests that assessed their identification accuracy for natural record...
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The Gold Medal is presented in the spring to a member of the Society, without age limitation, for contributions to acoustics. The first Gold Medal was presented in 1954 on the occasion of the Society's Twenty-Fifth Anniversary Celebration and biennially until 1981. It is now an annual award.
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It is clear that high-variability phonetic training can improve speech perception for adult second-language learners, but it is uncertain what levels of processing are responsible for this change and whether this interacts with the previous experience of the learners. The present study investigated these issues by giving auditory training to French...
Article
This study used the High-Variability Phonetic Training (HVPT) technique to train Finnish speakers to distinguish English vowels. It was found that Finnish speakers tend to use durational cues (which are phonemically relevant in their own language) to make a vowel category distinction rather than the relevant spectral cues. We used duration-modified...
Article
Non-native accents affect speech recognition in noise, and previous work has shown that intelligibility is modulated by listener-talker interaction; a matched linguistic background between the two seems to maximise intelligibility. The present study examined the contribution of segmental and supra-segmental cues, as well as how the degree of L2 exp...
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Previous studies have demonstrated that perceptual training improves both perception and production by adult second-language (L2) learners. The present study examined whether production training likewise improves both perception and production. Japanese speakers underwent ten sessions of production training for English r and l. The training combine...
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This study examined whether individuals with a wide range of first-language vowel systems (Spanish, French, German, and Norwegian) differ fundamentally in the cues that they use when they learn the English vowel system (e.g., formant movement and duration). All subjects: (1) identified natural English vowels in quiet; (2) identified English vowels...
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This study investigated changes in vowel production and perception among university students from the north of England, as individuals adapt their accent from regional to educated norms. Subjects were tested in their production and perception at regular intervals over a period of 2 years: before beginning university, 3 months later, and at the end...
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This study examined whether native speakers of Spanish and German learn differently when given auditory training for English vowels. Spanish has fewer vowels (5) than does German (18). Spanish speakers thus need to acquire more vowel categories when learning English than do Germans, but the relative sparseness of the Spanish vowel space may actuall...
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Vouloumanos and Werker (2007) claim that human neonates have a (possibly innate) bias to listen to speech based on a preference for natural speech utterances over sine-wave analogues. We argue that this bias more likely arises from the strikingly different saliency of voice melody in the two kinds of sounds, a bias that has already been shown to be...
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Previous work has demonstrated that normal-hearing individuals use fine-grained phonetic variation, such as formant movement and duration, when recognizing English vowels. The present study investigated whether these cues are used by adult postlingually deafened cochlear implant users, and normal-hearing individuals listening to noise-vocoder simul...
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This study compared how first-language Spanish and German speakers learn English vowels via computer-based auditory training. Spanish has fewer vowels than German, and thus Spanish speakers may have more unused room in their vowel space for new category learning. However, our results demonstrated that Germans improved twice as much (20 percentage p...
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This study tested native speakers of Norwegian, German, French, and Spanish on their recognition and production of L2 English vowels. A goodness‐optimization method was used to construct phonetically detailed perceptual vowel space maps for each listener’s L1 and L2 (English). These maps comprised best exemplar locations in a multidimensional stimu...
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Patterns of developmental change in phonetic perception are critical to theory development. Many previous studies document a decline in nonnative phonetic perception between 6 and 12 months of age. However, much less experimental attention has been paid to developmental change in native-language phonetic perception over the same time period. We hyp...
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Recent work [Iverson et al. (2003) Cognition, 87, B47-57] has suggested that Japanese adults have difficulty learning English /r/ and /l/ because they are overly sensitive to acoustic cues that are not reliable for /r/-/l/ categorization (e.g., F2 frequency). This study investigated whether cue weightings are altered by auditory training, and compa...
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This study investigated plasticity in speech production and perception among university students, as individuals change their accent from regional to educated norms. Subjects were tested before beginning university, 3 months later and on completion of their first year of study. At each stage they were recorded reading a set of test words and a shor...
Article
High‐variability phonetic training (HVPT) techniques have been successful for helping Japanese adults learn the English /r/–/l/ distinction. This success has been attributed to the fact that HVPT exposes listeners to naturalistic phonetic variability, from many talkers and phonetic contexts [e.g., Logan et al., J. Acoust. Soc. Am. 89, 874–886 (1991...
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Two experiments investigated whether listeners change their vowel categorization decisions to adjust to different accents of British English. Listeners from different regions of England gave goodness ratings on synthesized vowels embedded in natural carrier sentences that were spoken with either a northern or southern English accent. A computer min...
Article
This study examined whether cochlear implant users must perceive differences along phonetic continua in the same way as do normal hearing listeners (i.e., sharp identification functions, poor within-category sensitivity, high between-category sensitivity) in order to recognize speech accurately. Adult postlingually deafened cochlear implant users,...
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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. Sup...
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Two experiments investigated whether listeners change their vowel categorization decisions to adjust to different accents of British English. Listeners from different regions of England gave goodness ratings on synthesized vowels embedded in natural carrier sentences that were produced in either a northern or southern accent by a single male speake...
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Existing methods for examining phonetic categorization (i.e., identification or goodness judgments) typically require listeners to give responses on every member of a stimulus set. This article describes a new method that is more efficient for higher-dimensional stimulus sets (i.e., more phonetic detail) in which the number of perceptually distinct...
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This talk will outline a new theory that describes how distortions in auditory processing, due to language experience or to hearing impairment, can interfere with phonetic categorization processes. Experimental data will be presented on the perception of American English /r/ and /l/ by American and Japanese listeners. Native-language tests of adult...
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When talkers attempt to speak clearly in response to known perceptual difficulties on the part of the talker, they typically modify their speech patterns to include
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Speech perception by cochlear implant users is marked by large individual differences in word recognition accuracy. The aim of the present study was to examine whether these individual differences in speech understanding are correlated with measures of phonetic sensitivity and categorization. Thirty adult post‐lingually deafened cochlear implant pa...
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Formant movement and duration have been increasingly shown to be important cues for vowel recognition by normal-hearing adults; individuals enhance formant movement and duration contrasts when speaking clearly, and vowel recognition accuracy declines when these differences are reduced in signal-processed or synthesized speech. This study investigat...
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Previous work has emphasized the role of early experience in the ability to accurately perceive and produce foreign or foreign-accented speech. This study examines how listeners at a much later stage in language development-early adulthood-adapt to a non-native accent within the same language. A longitudinal study investigated whether listeners who...
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This study investigated the extent to which results from /r/ and /l/ perceptual identification training generalized to identification of novel natural stimuli and discrimination of synthetic stimuli in ten native Japanese speakers. A behavioral training software program was used which incorporated factors known to affect the acquisition of phonemic...