Only children and cognitive ability in childhood: a cross-cohort analysis over 50 years in the U.K.

Alice Goisis , University College London
Jenny Chanfreau, University College London (UCL)
George Ploubidis, UCL Centre for Longitudinal Studies
Vanessa Moulton, Centre for Longitudinal Studies, University College London

With declining family size and a gradual shift in family size ideals, only child families are expected to become more common in many advanced societies. Although previous research shows that in terms of cognitive outcomes only children tend to do as well as children with few siblings and better than children from large families, other studies show that they experience a disadvantage. One potential explanation for the mixed results across studies is that they cover different time periods: if the selection mechanisms into the formation of only child families change over time, the development of only children compared to children growing up with siblings could, as a consequence, also vary over time. In this study, using data from four UK birth cohorts (born in 1946, 1958, 1970, 2000-2002), we test whether the association between cognitive ability at age 10/11 and being an only child has changed over time and, if so, whether it is explained by cross-cohort differences in the characteristics of only child families. The results show that only children have higher cognitive scores than children who grow up with siblings but also that the advantage has weakened over time – which is consistent with the evidence that across the cohorts analysed only children have become a more heterogenous and disadvantaged group. Adjustment by family socio-demographic characteristics attenuates within and cross cohort differences. Taken together, the findings underscore that the selection process into being an only child is important in explaining the link between only childness and cognitive ability in childhood and how it varies over time and across studies.

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 Presented in Session P1. Postercafe