Causal language is essential for children’s language development, helping them understand and explain the reasons behind events. This study focuses on children’s causal language production and the role of parental input, aiming to (1) investigate differences in maternal and paternal language use, (2) analyse children’s causal language production across tasks and communication partners, and (3) examine the relationship between parental input and children’s causal language skills. Sixty children aged 4–5 and their parents participated in dyadic sessions, which included free play, guided play, and storytelling tasks. Results showed that fathers used more causal language than mothers during free play, and children also produced more causal language with their fathers in this context compared to storytelling. Overall, both maternal and paternal causal language inputs were linked to children’s causal language production, highlighting the significant influence of parental input on language development.

Both the quantity and quality of the maternal language input are important for early language development. However, depression and anxiety can negatively impact mothers’ engagement with their infants and their infants’ expressive language abilities. Australian mother-infant dyads (N = 30) participated in a longitudinal study examining the effect of maternal language input when infants were 24 and 30 months and maternal depression and anxiety symptoms on vocabulary size. Half the mothers had elevated depression and anxiety symptoms during at least one point in the study (at 6, 12, 18, 24, or 30 months). The results showed that only maternal input measures (word tokens, types, and mean length of utterance) predicted vocabulary size. While no evidence was found that brief periods of maternal depression and anxiety negatively impacted early vocabulary development, the findings highlight the critical importance and possible mitigating effects of maintaining good quality mother–infant interactions during early development.

Maternal input influences language development in children with Down syndrome (DS) and typical development (TD). Telegraphic input, or simplified input violating English grammatical rules, is controversial in speech–language pathology, yet no research to date has investigated whether mothers of children with DS use telegraphic input. This study investigated the quality of linguistic input to children with DS compared to age-matched children with TD, and the relationship between maternal input and child language abilities. Mothers of children with DS simplified their input in multiple ways, by using a lower lexical diversity, shorter utterances, and more telegraphic input compared to mothers of children with TD. Telegraphic input was not significantly correlated with other aspects of maternal input or child language abilities. Since children with DS demonstrate specific deficits in grammatical compared to lexical abilities, future work should investigate the long-term influence of maternal telegraphic input on language development in children with DS.