Lexical function of pitch in the first language shapes cross-linguistic perception of Thai tones

Determining the factors involved in the non-native perception of the pitch patterns of tones is complicated by the fact that all languages use pitch to various extents, whether linguistic (e.g., intonation) or non-linguistic (e.g., singing). Moreover, many languages use pitch to distinguish lexical items with varying degrees of functional load and differences in inventory of such pitch patterns. The current study attempts to understand what factors determine accurate naive (= non-learner) perception of non-native tones, in order to establish the baseline for acquisition of a tonal L2. We examine the perception of Thai tones (i.e., three level tones, two contour tones) by speakers of languages on a spectrum of lexically contrastive pitch usage: Mandarin (lexical tone), Japanese (lexical pitch accent), English (lexical stress), and Korean (no lexically contrastive pitch). Results suggest that the importance of lexically contrastive pitch in the L1 influences non-native tone perception so that not all non-tonal language speakers possess the same level of tonal sensitivity, resulting in a hierarchy of perceptual accuracy. Referencing the Feature Hypothesis (McAllister et al. 2002), we propose the Functional Pitch Hypothesis to model our findings: the degree to which linguistic pitch differentiates lexical items in the L1 shapes the naive perception of a non-native lexically contrastive pitch system, e.g., tones.