Mothers’ speech predicts children’s differences in cognition, literacy, and educational achievement across the school years

Children from well-resourced families achieve, on average, higher grades and gain more qualifications than those from under-resourced families. Mothers' speech is likely a key driver of the transmission of family background inequality in education. Yet, long-term associations between mothers' speech and children's education-related outcomes beyond the early years have not been studied previously. Here, we quantified differences in mothers' vocabulary sophistication, lexical diversity, and grammatical complexity from 10-minute-long naturalistic speech samples audio-recorded when children were age 5 and starting formal education. Children completed measures of cognition at age 5 and measures of literacy at ages 7 and 10 years; teachers rated their educational achievement at ages 7, 10, and 12 years. Data came from E-Risk, a UK cohort study that recruited families with twins born in 1994 and 1995 who represented the full range of Britain's socioeconomic conditions (analytic sample N = 894 mother-child trios). Mothers' vocabulary sophistication significantly predicted children's cognition, literacy, and educational achievement between the ages of 5 and 12 years, accounting for 2% to 5% of the variance. These estimates were reduced to 1% and 2% or became altogether non-significant after adjusting for mothers' educational attainment and household income. Our findings suggest that mothers' speech plays a small independent role in the long-term transmission of family background inequality in education.