This study investigated whether native listeners processed speech differently from non-native listeners in a speech detection task. Detection thresholds of Mandarin Chinese and Korean vowels and non-speech sounds in noise, frequency selectivity, and the nativeness of Mandarin Chinese and Korean vowels were measured for Mandarin Chinese- and Korean-native listeners. The two groups of listeners exhibited similar non-speech sound detection and frequency selectivity; however, the Korean listeners had better detection thresholds of Korean vowels than Chinese listeners, while the Chinese listeners performed no better at Chinese vowel detection than the Korean listeners. Moreover, thresholds predicted from an auditory model highly correlated with behavioral thresholds of the two groups of listeners, suggesting that detection of speech sounds not only depended on listeners' frequency selectivity, but also might be affected by their native language experience. Listeners evaluated their native vowels with higher nativeness scores than non-native listeners. Native listeners may have advantages over non-native listeners when processing speech sounds in noise, even without the required phonetic processing; however, such native speech advantages might be offset by Chinese listeners' lower sensitivity to vowel sounds, a characteristic possibly resulting from their sparse vowel system and their greater cognitive and attentional demands for vowel processing.
This research was supported by a University of Texas at Austin Research Grant. The authors thank Mark A. Hasegawa-Johnson and two anonymous reviewers for their constructive comments. The authors also thank Michelle Schoenecker for her assistance with manuscript preparation.
I. INTRODUCTION II. METHODS A. Stimuli 1. Experiment 1—Threshold of speech and non-speech detection in noise 2. Experiment 2—Frequency selectivity 3. Experiment 3—Nativeness rating of speech sounds B. Listeners 1. Experiments 1 and 2 2. Experiment 3 C. Procedure 1. General procedure 2. Procedure of Experiments 1 and 2—Signal detection in noise 3. Computation of the auditory filter bandwidths 4. Auditory model to predict vowel detection thresholds in LTSSN 5. Experiment 3—Nativeness rating of speech sounds III. RESULTS A. Experiment 1—Detection thresholds of speech and non-speech signals B. Experiment 2—Auditory filter bandwidth (frequency selectivity) C. Experiment 3—Nativeness rating of speech sounds IV. DISCUSSION A. Detection of non-speech and speech sounds in noise 1. Detection of non-speech and speech sounds 2. Detection of vowels for native and non-native listeners B. Application and future research C. Summary
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