Leong, Christine Xiang Ru
(2017)
Spoken English discrimination (SED) training with multilingual Malaysians: effect of adaptive staircase procedure and background babble in high variability phonetic training.
PhD thesis, University of Nottingham.
Abstract
High variability phonetic training (HVPT) has been shown to improve non-native speakers’ perceptual performance in discriminating difficult second language phonemic contrasts (Bradlow, Akahane-Yamada, Pisoni, & Tohkura, 1999; Bradlow, Pisoni, Akahane-Yamada, & Tohkura, 1997; Lively, Logan, & Pisoni, 1993; Lively, Pisoni, Yamada, Tohkura, & Yamada, 1994; Logan, Lively, & Pisoni, 1991). The perceptual learning can be generalized to novel words (Wang & Munro, 2004), novel speakers (Nishi & Kewley-Port, 2007; Richie & Kewley-Port, 2008) and even to speech production (Bradlow et al., 1997). However, the rigidity of the laboratory training settings has limited applications to real life situations.
The current thesis examined the effectiveness of a new phonetic training program - the Spoken English Discrimination (SED) training. SED training is a computerized individual training program designed to improve non-native speakers’ bottom-up perceptual sensitivity to discriminate difficult second language (L2) phonemic contrasts. It combines a number of key training features including 1) natural spoken stimuli, 2) highly variable stimuli spoken by multiple speakers, 3) multi-talker babble as background noise and 4) an adaptive staircase procedure that individualizes the level of background babble.
The first experiment investigated the potential benefits of different versions of the SED training program. The effect of stimulus variability (single speaker vs. multiple speakers) and design of background babble (constant vs. adaptive staircase) were examined using English voiceless-voiced plosives /t/-/d/ phonemic contrast as the training materials. No improvements were found in the identification accuracy on the /t/-/d/ contrast in post-test, but identification improvements were found on the untrained English /ε/-/æ/ phonemic contrast.
The effectiveness of SED training was re-examined in Chapter 3 using the English /ε/-/æ/ phonemic contrast as the training material. Three experiments were conducted to compare the SED training paradigms that had the background babble implemented either at a constant level (Constant SED) or using the adaptive staircase procedure (Adaptive Staircase SED), and the longevity of the training effects. Results revealed that the Adaptive Staircase SED was the more effective paradigm as it generated greater training benefits and its effect generalized better to the untrained /t/-/d/ phonemic contrast. Training effects from both SED paradigms retained six months after the last training section.
Before examining whether SED training leads to improvements in speech production, Chapter 4 investigated the phonetics perception pattern of L1 Mandarin Malaysian speakers, L1 Malaysian English speakers and native British English speakers. The production intelligibility of the L1 Mandarin speakers was also evaluated by the L1 Malaysian English speakers and native British English speakers. Single category assimilation was observed in both L1 Mandarin and L1 Malaysian English speakers whereby the /ε/ and /æ/ phonetic sounds were assimilated to a single/æ/ category (Best, McRoberts, & Goodell, 2001). While the British English speakers showed ceiling performance for all phonetic categories involved, the L1 Malaysian English speakers had difficulty identifying the British English /ε/ phoneme and the L1 Mandarin speakers had difficulty identifying the /d/ final, /ε/ and /æ/ phonemes. As seen by their perceptual performance, the L1 Mandarin speakers also had difficulty producing distinct /d/ final, /ε/ and /æ/ phonemes.
Two experiments in Chapter 5 examined whether the effects of SED training generalizes to speech production. The results showed that L1 Malaysian English speakers and native British English speakers found different SED paradigms to be more effective in inducing the production improvement. Only the production intelligibility of the /æ/ phoneme improved as a result of SED training.
Collectively, the seven experiments in this thesis showed that SED training was effective in improving Malaysian speakers’ perception and production performance of difficult English phonemic contrasts. Further research should be conducted to examine the efficacy of SED training in improving speech perception and production across different training materials and in speakers who come from different language backgrounds.
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