Top-Down and Bottom-up Processing of Familiar and Unfamiliar Mandarin Dialect Tone Systems

Speech processing involves active integration of bottom-up and top-down information types. In the present study, we investigated the relative weighting of top-down expectedness and bottom-up lexical tone in the perception of familiar and unfamiliar lexical tone systems. Standard Mandarin and Chengdu Mandarin are mutually intelligible language varieties with comparable segmental and highly distinct tonal realizations. In a spoken semantic-plausibility judgment task, we manipulated whether a word was high-surprisal or low-surprisal given the preceding context and dialect-specific tone. All participants were native Standard Mandarin speakers with minimal Chengdu Mandarin experience. Lower judgment accuracy was observed when the stimulus was Chengdu Mandarin, and suggested that expectedness (i.e., top-down) information overrides tonal (i.e., bottom-up) information in sentence plausibility judgments. However, judgment response times to sentence surprisal were uniform across stimuli from both dialects, suggesting that speakers are aware of the surprisal conveyed by a non-standard tone, even if not used in their final decision. These findings reveal listener sensitivity to both top-down expectedness and bottom-up tone regardless of the initial tone reliability. For unfamiliar tone systems, top-down influence overrides bottom-up processing to access utterance meaning, but bottom-up processing is indeed present and may reflect rapid learning of the unfamiliar tone system.