The interaction between phonological information and pitch type at pre-attentive stage: an ERP study of lexical tones

Previous studies on the processing of lexical tones have typically confounded effects due to phonological information (different meanings of words signalled by syllables with different tonal categories) with effects due to specific acoustic information (pitch type: pitch height/pitch contour). The present study is designed to dissociate these two kinds of effects and further investigate the processing of lexical tones at pre-attentive stage by mismatch negativity (MMN). We chose level tones and contour tones in Cantonese to differentiate pitch height from pitch contour, and manipulated tonal category (within-category/across-category) to distinguish phonological information from acoustic information. The results showed clear interactions between tonal category and pitch type in MMN mean amplitude and peak latency, suggesting the interaction between phonological information and pitch type in the pre-attentive processing of lexical tones. These results are discussed in light of cognitive and neural mechanisms underlying auditory processing of lexical tones.