Individual differences in second-language vowel learning

Adults often have difficulty in acquiring non-native vowels especially when the vowel inventories in first (L1) and second language (L2) are very different. However, even when testing L2 groups with similar profiles, there are great individual differences in the perception and production of non-native sounds. Similarly, computer-based training studies of L2 sounds report that improvement after training can range greatly across individuals. This thesis explores possible sources of individual differences in Greek native speakers’ perception and production of Southern British English vowels. Study 1 examined the perceived relationship between English vowels (in /bVb/ and /bVp/ contexts) and Greek vowels along with English vowel discrimination by the same participants. Greek speakers were found to perceive English vowels via both spectral and temporal assimilation to their L1 categories despite the fact that Greek does not use duration in L1 vowel distinctions. Study 2 defined the endpoints for the synthetic vowel continua to be used in Study 3 using a best exemplars experiment. In study 3, Greek speakers from a homogenous population (in terms of L1 background, age of L2 learning, amount and quality of L2 input) were tested on a large test battery before and after receiving 5 sessions of high-variability perceptual training. The test battery examined their perception of natural and synthetic vowels in L1 (Greek) and L2 (English) and their frequency discrimination ability (F2 only) as well as their production of L2 vowels. Group results showed significant improvement in the trainees’ perception of natural L2 vowels and their L2 vowel production. However, large individual differences were evident both before and after training. Vowel processing in L2 was found to relate to individual variability in vowel processing in L1 and, importantly, to frequency discrimination acuity, a finding that favours an auditory processing hypothesis for L1 and L2 speech perception of vowels

Plasticity in second language (L2) learning: perception of L2 phonemes by native Greek speakers of English

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Understanding the process of language acquisition is a challenge that many researchers spanning different disciplines (e.g. linguistics, psychology, neuroscience) have grappled with for centuries. One which has in recent years attracted a lot of attention has been in the area of non-native phoneme acquisition. Speech sounds that contain multiple phonetic cues are often difficult for foreign-language learners, especially if certain cues are weighted differently in the foreign and native languages. Greek adult and child speakers of English were studied to determine which cues (duration or spectral) they were using to make discrimination and identification judgments for an English vowel contrast pair. To this end, two forms of identification and discrimination tasks were used: natural (unedited) stimuli and another ‘modified’ vowel duration stimuli which were edited so that there were no duration differences between the vowels. Results show the Greek speakers were particularly impaired when they were unable to use the duration cue as compared to the native English speakers. Similar results were also obtained in control experiments where there was no orthographic representation or where the stimuli were cross-spliced to modify the phonetic neighborhood. Further experiments used high-variability training sessions to enhance vowel perception. Following training, performance improved for both Greek adult and child groups as revealed by post training tests. However the improvements were most pronounced for the child Greek speaker group. A further study examined the effect of different orthographic cues that might affect rhyme and homophony judgment. The results of that study showed that Greek speakers were in general more affected by orthography and regularity (particularly of the vowel) in making these judgments. This would suggest that Greek speakers were more sensitive to irrelevant orthographic cues, mirroring the results in the auditory modality where they focused on irrelevant acoustic cues. The results are discussed in terms of current theories of language acquisition, with particular reference to acquisition of non-native phonemes.School of Social Sciences, Brunel Universit

The Development and Evaluation of the Hearing Intervention Battery in Arabic (HIBA) for Auditory Perception in Children with Cochlear Implants

The Hearing Intervention Battery in Arabic (HIBA), is a multi-modal auditory training intervention, that was developed based on the recommendations from our published systematic review of the literature on the effectiveness of auditory training (AT) for children with cochlear implants (CIs). HIBA was primarily intended to help improve speech and pitch perception in Arabic-speaking children with CIs. Due to the lack of auditory and speech assessment tools for the Arabic language, the A-CAPT, an Arabic version of the English Chear Auditory Perception Test (CAPT) was developed. The A-CAPT was validated prior its use in this project with 26 children with typical hearing. There was a strong agreement between the test and retest measures and normative data and the critical difference values were calculated which were similar to the British English CAPT. A randomized control trial (RCT) to evaluate the HIBA training programme was conducted with 14, 5- to 13-year-old Arabic-speaking children with CIs. The control group received art training following step-by-step drawing and face-paint exercises while the HIBA multi-modal training group received games involving communication interactions (DiaPix), speech cue discrimination (Alefbata.com), and pitch discrimination (musical discrimination using a keyboard). All tasks were interactive and designed to be completed by the children together with their parents or caregivers. There was a double baseline measurement, followed by a 4-week intervention period before a post intervention assessment. There was a significant improvement in consonant perception for children who received the HIBA multi-modal training intervention but this was not observed in the active control group. There was some evidence of generalization of learning, as observed by improvements in the non-trained task (phoneme discrimination) for the intervention group but not for controls. It was unclear if one particular element of the HIBA led to these improvements. Parents were actively involved in the multi-modal training group and their feedback indicated that the most preferred part of multi-modal training was the communication interaction tasks using the Diapix. To understand which element of the HIBA led to improvements in speech perception and whether the duration of training and sample size masked any gains, a trial forward in a larger scale should be conducted. In addition, to improve the quality of evidence of the study, collaboration is need to achieve a double blinded study and minimize bias. Findings of this project may suggest that children with CIs and their parents can benefit from regular and sustained access to age-appropriate auditory training materials and activities. In addition, findings would extend the current understanding of the impact of auditory training on CI outcomes in children and provide inspiration for a more comprehensive rehabilitation scheme for CI users

Perception and production of English vowels by Chilean learners of English: effect of auditory and visual modalities on phonetic training

The aim of this thesis was to examine the perception of English vowels by L2 learners of English with Spanish as L1 (Chilean-Spanish), and more specifically the degree to which they are able to take advantage of visual cues to vowel distinctions. Two main studies were conducted for this thesis. In study 1, data was collected from L2 beginners, L2 advanced learners and native speakers of Southern British English (ENS). Participants were tested on their perception of 11 English vowels in audio (A), audiovisual (AV) and video-alone (V) mode. ENS participants were tested to investigate whether visual cues are available to distinguish English vowels, while L2 participants were tested to see how sensitive they were to acoustic and visual cues for English vowels. Study 2 reports the outcome of a vowel training study. To compare the effect of different training modalities, three groups of L2 learners (beginner level) were given five sessions of high-variability vowel training in either A, AV or V mode. Perception and production of English vowels in isolated words and sentences was tested pre/post training, and the participants’ auditory frequency discrimination and visual bias was also evaluated. To examine the impact of perceptual training on L2 learners’ vowel production, recordings of key words embedded in read sentences were made pre and post-training. Acoustic-phonetic analyses were carried out on the vowels in the keywords. Additionally, the vowels were presented to native listeners in a rating test to judge whether the perceptual training resulted in significant improvement in intelligibility. In summary, the study with native English listeners showed that there was visual information available to distinguish at least certain English vowel contrasts. L2 learners showed low sensitivity to visual information. Their vowel perception improved after training, regardless of the training mode used, and perceptual training also led to improved vowel production. However, no improvement was found in their overall sensitivity to visual information

Speech production and perception in adult Arabic learners of English: A comparative study of the role of production and perception training in the acquisition of British English vowels

This thesis presents the results of four studies that investigated the perception and production of English by Saudi Arabic learners. Additionally, the thesis sought to investigate the role of different types of training, production- or perception-based, in learning, with the aim of understanding how training in different domains contributes to second language acquisition. A preliminary study (Study 1) investigated problematic phonemic contrasts for Arabic speakers, confirming that accuracy in perception and production depends on the similarity between L1 and L2 phonemes. Study 2 investigated the specificity of second language phonetic training by comparing the effect of three training programmes on the acquisition of British English vowels. Saudi Arabic learners were randomly assigned to one of three training programmes; Production Training (PT), High Variability Phonetic Training (HVPT), and a Hybrid Training Program (HTP). They completed a battery of tests before and after training. All participants improved after training, but improvements were largely domain-specific; production training led to improvements in production but not perception, whilst perception training led to improvements in perception but not production. Participants in the HTP showed improvements in both production and perception, indicating that only a small amount of training in production appears to be necessary to effect changes in production. Additionally, improvement on particular tasks appeared to be linked to initial L2 proficiency, and learning in perception and production was retained (Study 3) and production training appeared to be more beneficial for participants who were trained in a non-immersion setting (Study 4). In brief, the results suggest that L2 learners improve in both perception and production if training explicitly trains these domains. Production training was beneficial not only for L2 learners in an L2-speaking country, but also in non-immersion settings. Overall, these results suggest that a hybrid training programme would be most beneficial for L2 learners

Plasticity in second language (L2) learning : perception of L2 phonemes by native Greek speakers of English

Understanding the process of language acquisition is a challenge that many researchers spanning different disciplines (e.g. linguistics, psychology, neuroscience) have grappled with for centuries. One which has in recent years attracted a lot of attention has been in the area of non-native phoneme acquisition. Speech sounds that contain multiple phonetic cues are often difficult for foreign-language learners, especially if certain cues are weighted differently in the foreign and native languages. Greek adult and child speakers of English were studied to determine which cues (duration or spectral) they were using to make discrimination and identification judgments for an English vowel contrast pair. To this end, two forms of identification and discrimination tasks were used: natural (unedited) stimuli and another ‘modified’ vowel duration stimuli which were edited so that there were no duration differences between the vowels. Results show the Greek speakers were particularly impaired when they were unable to use the duration cue as compared to the native English speakers. Similar results were also obtained in control experiments where there was no orthographic representation or where the stimuli were cross-spliced to modify the phonetic neighborhood. Further experiments used high-variability training sessions to enhance vowel perception. Following training, performance improved for both Greek adult and child groups as revealed by post training tests. However the improvements were most pronounced for the child Greek speaker group. A further study examined the effect of different orthographic cues that might affect rhyme and homophony judgment. The results of that study showed that Greek speakers were in general more affected by orthography and regularity (particularly of the vowel) in making these judgments. This would suggest that Greek speakers were more sensitive to irrelevant orthographic cues, mirroring the results in the auditory modality where they focused on irrelevant acoustic cues. The results are discussed in terms of current theories of language acquisition, with particular reference to acquisition of non-native phonemes.EThOS - Electronic Theses Online ServiceSchool of Social Sciences, Brunel UniversityGBUnited Kingdo

Factors affecting the perception of noise-vocoded speech: stimulus properties and listener variability.

This thesis presents an investigation of two general factors affecting speech perception in normal-hearing adults. Two sets of experiments are described, in which speakers of English are presented with degraded (noise-vocoded) speech. The first set of studies investigates the importance of linguistic rhythm as a cue for perceptual adaptation to noise-vocoded sentences. Results indicate that the presence of native English rhythmic patterns benefits speech recognition and adaptation, but not when higher-level linguistic information is absent (i.e. when the sentences are in a foreign language). It is proposed that rhythm may help in the perceptual encoding of degraded speech in phonological working memory. Experiments in this strand also present evidence against a critical role for indexical characteristics of the speaker in the adaptation process. The second set of studies concerns the issue of individual differences in speech perception. A psychometric curve-fitting approach is selected as the preferred method of quantifying variability in noise-vocoded sentence recognition. Measures of working memory and verbal IQ are identified as candidate correlates of performance with noise-vocoded sentences. When the listener is exposed to noise-vocoded stimuli from different linguistic categories (consonants and vowels, isolated words, sentences), there is evidence for the interplay of two initial listening 'modes' in response to the degraded speech signal, representing 'top-down' cognitive-linguistic processing and 'bottom-up' acoustic-phonetic analysis. Detailed analysis of segment recognition presents a perceptual role for temporal information across all the linguistic categories, and suggests that performance could be improved through training regimes that direct attention to the most informative acoustic properties of the stimulus. Across several experiments, the results also demonstrate long-term aspects of perceptual learning. In sum, this thesis demonstrates that consideration of both stimulus-based and listener-based factors forms a promising approach to the characterization of speech perception processes in the healthy adult listener

Hakka tone training for native speakers of tonal and nontonal languages

Language learning becomes increasingly difficult when novel linguistic features are introduced. Studies have shown that learners from various language backgrounds can be trained to perceive lexical tone, which assigns meaning to words using variations in pitch. In this thesis, we investigated whether native speakers of tonal Mandarin Chinese and tonal Vietnamese outperformed native speakers of nontonal English when learning Hakka Chinese tones following five sessions of tone training, and whether the complexity (i.e., density) of a listener’s native tone inventory facilitated nonnative tone learning. All groups improved in tone identification and tone word learning following training, with improvements persisting three weeks following the cessation of training. Although both tonal groups outperformed the English group in most tasks, the Mandarin group showed the most consistent advantages over the English group across tasks. Findings suggest that tone experience bolsters tone learning, but density of the tone inventory does not provide an advantage. Confusion patterns offer detailed insight of the interaction between nonnative tones and native tonal and intonational categories