The diversity of tone languages and the roles of pitch variation in non-tone languages : considerations for tone perception research

All languages employ consonants and vowels as discrete contrastive subcomponents of the basic timing units of words (syllables). These two classes of phonemes are used to differentiate between words, whose meanings can be categorically changed by switching even a single vowel or consonant, as in vs. or . They populate the lowest level of the phonological hierarchy, the segmental tier, and both classes are obligatory across spoken languages. But only some languages also make use of lexical tones, contrastive sub-syllabic fundamental frequency (pitch) variations referred to as tonemes (e.g., Jones, 1944), which for those languages comprise a third class of phonemic elements. Perceptual researchers often assume tones to be suprasegmental (e.g., So and Best, 2010, 2011, 2014; Liu et al., 2018; Poltrock et al., 2018), i.e., to extend across the consonants and vowels of the target syllable. While in a phonetic sense tones extend across the voiced segments of a syllable, however, such observations may not straightforwardly reflect the more abstract phonological properties of tones (e.g., see Wang, 1967; Hyman, 2011a,b). Indeed, several tone phonologists claim that lexical tones function as segments in tone languages (e.g., Lin, 1989; Duanmu, 1990, 1994). For the following paragraphs we adopt that phonological view that lexical tones function in tone languages at the segmental level, along with consonants and vowels. However, we return later to consider their phonological status and its relevance for understanding lexical tone perception by native and non-native listeners.