Categorical Perception of Lexical Tone by Tonal and Non-tonal Language Speakers

Categorical perception occurs when a physical continuum is perceived discontinuously. In speech, a vast body of research has shown that consonants are perceived categorically whereas vowels are perceived continuously. The other major phonetic unit of speech, lexical tone, has been relatively neglected in categorical perception studies. Here tonal language (Thai), and non-tonal language (Australian English) listeners are tested for their categorical perception of three artificial tone continua (mid-rise, mid-fall, rise-fall) in four different contexts, speech, filtered speech, music, and sine waves. Thai listeners were found to perceive speech continua significantly more categorically than Australian English listeners, but for the non-speech continua perception was equivalent for the two language groups. The results indicate that the categorical perception of tone is to some extent learned.