Exploring word-referent mapping in Mandarin-speaking late-talkers at 33 months and its language predictors at 27 months: An eye-tracking study

Background and Aims

This longitudinal study investigated the language skills, phonological working memory and lexical-tone perception of Mandarin-speaking late-talkers (LTs) and those with typical language development (TLD) at 27 months, while also examining their connections with novel word-referent mapping (W-R mapping) through eye-tracking at 33 months.

Methods and Procedures

Participants included 22 Mandarin-speaking 27-month-old LTs and 22 toddlers with TLD. Data on expressive and receptive language abilities, as well as phonological working memory and lexical-tone perception, were collected when participants were 27 months old. An eye-tracking paradigm was further employed during the word-learning tasks, which included W-R mapping and word-identification test (W-I test) phases at 33 months. Multilevel models were used to analyse participants’ gaze pattern trajectories.

Outcomes and Results

At 27 months, LT toddlers exhibited poorer language skills (receptive: p = 0.015, expressive: p < 0.001), lexical-tone perception (p < 0.001) and phonological working memory (p < 0.001) compared to those with TLD, even after considering maternal educational level and participants’ fine motor ability. During the W-I test phase, we observed that LT toddlers showed a slower increase in fixations on the novel target image while listening to the corresponding novel word over time, compared to TLD toddlers (linear: p = 0.011, quadratic: p = 0.007) after adding confounders. Further, expressive language ability at 27 months old was a predictor of their newly established W-R mappings at 33 months old (p = 0.016). Additionally, the toddler's phonological working memory and lexical-tone perception were associated with their expressive language ability (p = 0.001 and < 0.001).

Conclusions and Implications

These findings indicate that the novel W-R mapping is not as robust in LTs as in TLDs, and the skills necessary for word learning share similarities with a wide range of expressive language abilities. Moreover, poor expressive language abilities were associated with deficits in lexical processing abilities; that is, phonological working memory and lexical-tone perception. These findings suggest the need for interventions aimed at improving LTs’ lexical processing abilities to strengthen their lagging word-learning skills at toddlerhood.

WHAT THIS PAPER ADDS

What is already known on this subject

• Late-talkers (LTs) exhibit delays in expressive vocabulary development. Furthermore, they also perform poorly in word learning.

What this paper adds to existing knowledge

• The eye-tracking paradigm was employed and found that novel word-referent mapping (W-R mapping) is not as robust in LTs as in those with typical language development. Toddlers’ early expressive language ability could predict their ability to establish novel W-R mappings. Furthermore, the better the phonological working memory and lexical-tone perception of LTs are, the better their early expressive language ability is.

What are the clinical implications of this work?

• Interventions might consider incorporating strategies to improve phonological working memory and lexical-tone perception to help Mandarin-speaking LTs enhance linguistic capacities and build robust novel W-R mapping.