Naturalistic observations of individual differences in children’s home environments

This thesis investigated associations between early life home environments and children’s linguistic, cognitive and behavioural outcomes. Markers of the home environment included characteristics of adult speech that children were exposed to (i.e., the quantity, lexical diversity and vocabulary sophistication), parenting behaviours, and literacy behaviours and beliefs. For children’s outcomes, their language (i.e., lexical diversity and vocabulary sophistication), non-verbal cognitive abilities, and behavioural responses were assessed. Naturalistic home observations were collected from 107 children, aged 24 to 48 months, and their families using LENA digital audio-recorders. All families completed 3 day-long audio-recordings for an average of 15.06 hours per day (SD = 1.87), making this the largest naturalistic observational study of British home environments to date. This thesis makes an original contribution by 1) exploring the association between early life experiences of language and parenting on children’s language, cognitive, and behavioural differences using naturalistic observations, 2) being the first to assess the lexical diversity and vocabulary sophistication of naturalistic speech collected by LENA audio-recorders, 3) conducting a novel psychometric assessment of parenting and child behaviours derived from audio-recordings, 4) providing empirical evidence of extreme within-family variability in children’s language exposure, which was not previously recognised, and 5) showing that parental literacy behaviours influence children’s cognitive abilities independent of the adult speech that they hear in the family home. The studies contained within this thesis provide support for the environmental specificity hypothesis which states that different aspects of child development have unique environmental predictors. The findings confirm the importance of language input for children’s language development and align with the usage-based theory of language acquisition. Overall, the environmental factors studied here were found to be important for children’s development and extremely dynamic. Utilising digital technologies to harness these dynamic environments may bring us closer to understanding how best to improve children’s outcomes.