Lexical tone is different and special: Evidence from a speeded repeated production task

Priming experiments and speech error studies have found cross-linguistic differences in phonological encoding. Notably, the first selectable unit (the proximate unit) differs between English and Mandarin Chinese, with the former selecting segmental units like consonants (Cs) and vowels (Vs) first, while the latter selects syllables as a whole. Further, Mandarin Chinese is tonal, meaning the same syllable is a different word depending on the tone it is spoken with. However, it remains unclear how tone is represented and processed during phonological encoding in speech production - attached to the vowel or CV, or processed independently. Across three experiments, we investigated these questions by measuring how quickly speakers produced sequences of tone-bearing CV syllables. Unlike English, speed of production was not directly linked to plan reuse (see Sevald & Dell, 1994). Instead, speech rate was robustly faster when each CV was produced with only one tone (i.e., about equal speech rate for ba2 di1 da1 bi2 and ba1 ba1 ba1 ba1), compared to when a particular CV was produced with more than one tone (i.e., slower speech rate for ba1 ba2 ba1 ba2). We suggest that Mandarin speakers represent CVs as syllable "chunks," integrating tone-a part of the structural frame with the CV (rather than a vowel), and producing the same CV with more than one tone in a sequence is difficult as a result of needing to reassign different tones to the same CV chunk.