Reciprocal Influences between Child and Parent Language in Dyads Involving High- and Low-Risk Infants for Autism
The important role of parental linguistic input in children’s language learning has been well documented in typical and atypical development (Bang & Nadig, 2015; Rowe, 2012). Yet, less research has explored how infants may impact parent language and shape their own environment (Fusaroli et al., 2019).
We conducted a longitudinal investigation of (1) infant language production; (2) parent language production; and (3) reciprocal associations between infant and parent language measures in dyads involving infants at high and low familial risk for autism spectrum disorder (ASD) at 12, 18, and 24 months.
Eighty-nine mother-infant dyads were videotaped in the lab during a 10-minute interaction at 12, 18, and 24 months. Infants’ and parents’ language from each session was transcribed and analyzed for quantity and quality. The total number of words (word tokens) served as the measure of quantity. The total number of different words (word types) and linguistic complexity (mean length of utterance; MLU) served as the measures of quality. Infants’ ASD outcomes were determined using Autism Diagnostic Observation Schedule (Lord et al., 2000) and clinical judgment at 18-36 months. Based on their risk and ASD outcomes, infants were classified into three groups: high-risk infants diagnosed with ASD (HRA+), high-risk infants not diagnosed (HRA-), and low-risk comparison infants not diagnosed (LRC).
(1) There was no significant group difference in infant language measures at 12 months. However, HRA+ infants produced significantly fewer word tokens than LRC infants at 18 months (z= -2.40, p= .02) and 24 months (z = -2.64, p= .01). Also, HRA+ infants produced significantly fewer word types than HRA- (z= -2.00; p = .05) and LRC infants (z= -2.65, p= .01) at 24 months, displaying lower quantity and quality of talk beginning within the second year of life.
(2)There was no significant group difference in parent language measures at 12 months. While there was no significant group difference in quantity, parents’ talk significantly differed in quality at 18 and 24 months. At 18 months, HRA+ mothers produced significantly fewer word types than HRA- (z= -2.46, p= .01) and LRC mothers (z= -3.14, p< .01); HRA+ and HRA- mothers produced significantly shorter MLU than LRC mothers (z= -3.96, p< .001; z= -2.32, p= .02, respectively). At 24 months, HRA+ and HRA- mothers produced shorter MLU than LRC mothers (z= -2.44, p= .01; z = -2.82, p< .01, respectively).
(3) When examining the reciprocal effects of parent language on child language, we found that 18-month parent MLU was a significant, positive predictor of 24-month child MLU, when controlling for child ASD risk, sex, earlier MLU, and parent education. When examining the effects of child on parent language, child word types at 12 months was a significant, positive predictor of parent MLU at 24 months, controlling for the covariates.
High- and low-risk infants may shape their own linguistic environment over time, with their parents modulating linguistic input based on infant language.