This longitudinal study investigated modifications in lexical tones and intonation in Cantonese infant-directed speech (IDS) to children aged 15 and 23 months. The results showed that to children at both ages, mothers increased intonational pitch height and pitch variability across utterances, and produced lexical tones with generally larger tonal space and greater intra-talker tone variation within categories in IDS compared to adult-directed speech. No significant changes were found in either lexical tones or intonation in IDS between the two ages. In addition, positive correlations were found between the degree of age-related changes in tonal space and intonational exaggerations in IDS as children grow older. The findings were discussed with a focus on the co-occurrence of an increase in tone variation along with tonal space expansion, the age-related changes in lexical tones and intonation, and the associations between the lexical and prosodic pitch modifications.

Learners can track word-referent co-occurrences across individually-ambiguous naming events to form correct word-referent mappings, termed statistical word learning (SWL). Prior research largely focuses on learning from a single language input, where a referent co-occurs with a single word (1:1 mapping). Here, we tested adults’ SWL from a simulated bilingual environment, where one referent co-occurred with two words (2:1 mapping) and the two words were either differentiated by a linguistic cue (Mandarin lexical tones, Cued condition) or not (Uncued condition). Results showed that in the Cued condition, Chinese–English bilinguals (N = 38) outperformed Spanish–English bilinguals (N = 56) and English monolinguals (N = 55), while Spanish–English bilinguals and English monolinguals performed similarly. The three groups did not differ in the Uncued condition. Self-reported learning confidence and strategies showed limited conscious awareness of learning. Results demonstrate that familiarity with a linguistic cue boosts overall statistical word learning from bilingual input.

The functions of acoustic-phonetic modifications in infant-directed speech (IDS) remain a question: do they specifically serve to facilitate language learning via enhanced phonemic contrasts (the hyperarticulation hypothesis) or primarily to improve communication via prosodic exaggeration (the prosodic hypothesis)? The study of lexical tones provides a unique opportunity to shed light on this, as lexical tones are phonemically contrastive, yet their primary cue, pitch, is also a prosodic cue. This study investigated Cantonese IDS and found increased intra-talker variation of lexical tones, which more likely posed a challenge to rather than facilitated phonetic learning. Although tonal space was expanded which could facilitate phonetic learning, its expansion was a function of overall intonational modifications. Similar findings were observed in speech to pets who should not benefit from larger phonemic distinction. We conclude that lexical-tone adjustments in IDS mainly serve to broadly enhance communication rather than specifically increase phonemic contrast for learners.

Listeners can adapt to errors in foreign-accented speech, but not all errors are alike. We investigated whether exposure to unsystematic tone errors in second language Mandarin impacts responses to accurately produced words. Native Mandarin speakers completed a cross-modal priming task with words produced by foreign-accented talkers who either produced consistently correct tones, or frequent tone errors. Facilitation from primes bearing correct tones was unaffected by the presence of tone errors elsewhere in the talker's speech. However, primes bearing tone errors inhibited recognition of real words and elicited stronger accentedness ratings. We consider theoretical implications for tone in foreign-accent adaptation.

This study examines brain responses to boundary effects with respect to Mandarin lexical tone continua for three groups of adult listeners: (1) native English speakers who took advanced Mandarin courses; (2) naïve English speakers; and (3) native Mandarin speakers. A cross-boundary tone pair and a within-category tone pair derived from tonal contrasts (Mandarin Tone 1/Tone 4; Tone 2/Tone 3) with equal physical/acoustical distance were used in an auditory oddball paradigm. For native Mandarin speakers, the cross-category deviant elicited a larger MMN over left hemisphere sensors and larger P300 responses over both hemispheres relative to within-category deviants, suggesting categorical perception of tones at both pre-attentive and attentional stages of processing. In contrast, native English speakers and Mandarin learners did not demonstrate categorical effects. However, learners of Mandarin showed larger P300 responses than the other two groups, suggesting heightened sensitivity to tones and possibly greater attentional resource allocation to tone identification.

Both Standard Chinese (SC) high- and low-rising tones sound like the rising tone in Jinan Mandarin (JM) Chinese. Acoustically (Experiment 1), the JM rising tone overlaps with both SC rising tones, but more with the high-rising tone than with the low-rising tone. Perceptually (Experiment 2), the JM rising tone was more likely identified as the SC high-rising tone by SC monolinguals. Experiment 3 examined the role of this two-to-one interlingual tonal mapping in bilingual lexical access. Final high-rising SC pseudo-words were more frequently and more quickly accepted as JM real words than final low-rising SC pseudo-words were. However, both high- and low-rising SC pseudo-words triggered equivalent facilitatory semantic priming on JM real-word targets. The results suggest that different tones are represented in the bilinguals’ mental lexicon in terms of fine-grained and sometimes overlapping acoustic specifications. Lexical activation and semantic activation are partially independent.