Perceptual assimilation and discrimination of falling, level, and rising lexical tones by native English speakers

Perceptual assimilation model posits that the perceived relation of non-native sounds to native sound categories predicts the discriminability of non-native sounds [1]. This study examines whether the degree of perceived similarity between Vietnamese tones and English intonation patterns predicts the accuracy of tone-contrast discrimination. In a categorization task, ten native English speakers were asked to match falling, level, and rising tone words with five English intonation patterns. Then, in a discrimination task, they were asked to judge the similarity of Vietnamese tones to each other. In the first task, speakers perceived both of the falling and level tones as most similar to the statement intonation (Right), and the rising tone as most similar to the question intonation (Right?). These cross-language mappings averaged at 74%, 65% and 73% of responses, respectively, suggesting relatively reliable categorization of tones and predicting relatively low discrimination accuracy for the level-falling tone contrast. In the second task, however, level-falling tones were discriminated significantly better than level-rising tones. This suggests that assimilation of tones to different intonation patterns is not the sole predictor of tone discrimination accuracy.