Over the last 60 years, the percentage of children in the United Kingdom living in homes headed by a single mother has risen steadily. A new study examined how the impact of single motherhood on children's verbal cognitive abilities has changed and how the age of children when their parents separate affects those abilities. The study concluded that children who lived with a single mother before age 11 had lower verbal cognitive ability even after considering mothers' education and their age at the time of the child's birth.

The study was done by researchers at the University of Bristol, Universidad de Alcalá, and the University of Bath. It is published in Child Development, a journal of the Society for Research in Child Development.

"Our study shows that almost all of the relationships between single motherhood and negative consequences for children's cognitive attainment can be explained by families' reduced economic circumstances," explains Susan Harkness, professor of public policy at the University of Bristol, who led the study. "Although single motherhood has become much more common in the U.K., deficits associated with parenting--as opposed to reduced economic circumstances--have all but disappeared over the last 40 years."

Researchers used data from three large, nationally representative studies of British children born in 1958, 1970, and 2000; each study included more than 10,000 children and measured children's verbal ability on standardized tests at age 10 (1970 study) or 11 (1958 and 2000 studies). The studies also collected information on economic and family characteristics, as well as family members' health and well-being.

Prior studies, which used data from children born in the 1940s to the 1970s, compared children of single mothers with children in families that are otherwise similar but not headed by a single mother, so the indirect effect of single motherhood on children's outcomes is not well understood. In this study, researchers sought to determine how the family environment is affected by single motherhood, specifically, to what extent the economic and parenting resources of children in single- and two-parent families differ. They then assessed how children in single-mother families might have done had their parents not separated, and how economic resources and differences in parenting affected children's attainment.

The study examined how being born to a single mother, having parents separate after birth but before age 7, and having parents separate between ages 7 and 11 affected children's verbal ability at age 11. It also assessed how single motherhood affected economic resources and parenting, and the impact that this in turn had on children's verbal ability. Children's cognitive ability is strongly related to a range of later life outcomes, including the likelihood of dropping out of school, earnings, occupational attainment, crime, substance abuse, and mental health.

The study found that:

Children who lived with a single mother before age 11 had lower verbal cognitive attainment than children whose parents stayed together.

For children born in 2000, the age at which their parents separated mattered to their attainment: Those whose parents separated before they were 7 had less optimal cognitive outcomes than those whose parents separated when they were between 7 and 11; the study saw no statistically significant effects for the latter group. This pattern differs from that of children born in 1958 or 1970; for these children, the age at which their parents separated had little effect on their attainment.

Few differences were identified in the parenting behavior of single- and two-parent families, and this contributed little to the observed differences in attainment, leading the researchers to conclude that lower attainment is largely due to single-mother families' lower economic resources.

"Overall, our findings suggest two policy responses in the U.K.: supporting the incomes of single-parent families, particularly those with very young children, and addressing the growing gap in attainment between all children whose parents have adverse economic characteristics, whether partnered or not," said Paul Gregg, professor of public policy at the University of Bath, who coauthored the study.

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The study was supported by the United Kingdom Economic and Social Research Council.

Summarized from Child Development, The Rise in Single-Mother Families and Children's Cognitive Development: Evidence from Three British Birth Cohorts, by Harkness, S (University of Bristol), Salgado, MF (Universidad de Alcalá), and Gregg, P (University of Bath). Copyright 2019 The Society for Research in Child Development, Inc. All rights reserved.