An eye-tracking study investigated how the interaction between syllable frequency and syllable-specific tonal probability guides online lexical access in speakers of mutually unintelligible Chinese dialects with three disparate tonal systems. Mono-dialectal Mandarin speakers, bi-dialectal Shanghai–Mandarin speakers and bi-dialectal Cantonese–Mandarin speakers searched for target Mandarin syllable–tone combinations while their eye movements and mouse clicks were recorded. The results showed dialectal differences in online eye fixation patterns but not in offline mouse responses. For all groups, mouse clicks were fastest for infrequent syllables with most probable tones and slowest for infrequent syllables with least probable tones. In online eye movement responses, only mono-dialectal Mandarin speakers showed an interaction between syllable frequency and tonal probability. Mono-dialectal Mandarin speakers’ fixations were fastest for infrequent syllables with probable tones and slowest for infrequent syllables with improbable tones. Mono-dialectal speakers also showed a greater amount of competition from the more probable segmental competitor when hearing improbable tones. Bi-dialectal speakers showed different timing in their integration of tonal probabilities. These findings suggest that highly bilingual speakers track and use Mandarin tonal probabilities, but their sensitivity to L2 tonal information may lag behind monolinguals for online word recognition.

Both off-line and on-line comprehension studies suggest not only toddlers and preschoolers, but also older school-age children have trouble interpreting contrast-marking pitch prominence. To test whether children achieve adult-like proficiency in processing contrast-marking prosody during school years, an eye-tracking experiment examined the effect of accent on referential resolution in six- to eleven-year-old children and adults. In all age groups, a prominent accent facilitated the detection of a target in contrastive discourse sequences (pink cat→greencat), whereas it led to a garden path in non-contrastive sequences (pink rabbit→greenmonkey: the initial fixations were on rabbits). While the data indicate that children as young as age six immediately interpret contrastive accent, even the oldest child group showed delayed fixations compared to adults. We argue that the children's slower recovery from the garden path reflects the gradual development in cognitive flexibility that matures independently of general oculomotor control.