A comparative study between the direct and overheard speech of primary caregiver of late talkers and typically developing infants

Objectives: Mother's language input is the most meaningful and impactful features for toddlers' language development. The more children experience successful communication between mothers and the child the greater the positive effects on a child's lingual development. This study examines the frequency of linguistic stimulation input, and the linguistic competencies of late-talking infants. Methods: Thirty-two pairs of mothers and children participated in this study: 16 pairs of late-talking (LT) infants (18-36 months) with their mothers and 16 pairs of typically developing (TD) infants of the same age with their mothers. The mothers had a smartphone attached to their armbands that recorded child-direct speech and speech overhead by their children during the course of a week in their daily lives. Results: The results showed that the group of TD children's mothers had significantly higher child-directed speech than the group of LT children's mothers. Among 6 different subtypes of child-directed speech, LT mothers group showed higher results in 'questioning,' 'demanding' than the TD mothers group; the LT mothers group showed lower in 'responding,' 'explanation & naming,' and 'attempting.' Conclusion: The experiment provided an evidence that the direct linguistic interaction between mother and child is an important factor for children's language development, and identifies language types used by mothers interacting with their children.