A group of cognitive processes called “executive functions” are important for regulating behavior, managing new and potentially confusing information, adjusting to school, and making academic progress in the early elementary grades. But why do poor kids have less advanced executive functioning and start school at a disadvantage?

“Stress in the lives of poor children is one cause of the early achievement gap in which children from low-income homes start school behind their more advantaged classmates.” So says Clancy Blair, professor of applied psychology at New York University and lead researcher of a novel study examining the relationship between poverty, parenting, stress and cognitive ability in young children.

Previous research has revealed individual pieces of the puzzle. It has been known for some time, for example, that children living in poverty score lower on tests of executive function – the ability to plan and carry out tasks – than children from better-off families. Similarly, research has shown that poor parenting has an impact on executive function. And research has shown that high stress levels influence young children’s brain development in ways that may damage their ability to regulate their own behavior and to plan and carry out tasks.

But this is the first time these individual puzzle pieces have been slotted together. Bringing them together suggests that children from low-income homes may be, on average, exposed to less positive parenting, which increases their stress levels, which in turn damages self-regulation and executive functioning.

Parenting, stress, and executive function
Blair, and a team of researchers from several US universities, studied the early environments of 1,300 young children in mostly low-income homes between the ages of 7 and 24 months. They collected data on demographic characteristics, the household environment (such as safety and noise levels), and the quality of parenting (for example, levels of mothers’ sensitivity, detachment, and intrusiveness when interacting with their children). They also examined children’s stress by measuring levels of the stress hormone cortisol and measured executive functions via a collection of tests administered when the children were three years old.

The researchers found that children in lower-income homes received less positive parenting and had higher levels of cortisol in their first two years than children in slightly better-off homes. Crucially, higher levels of cortisol were, in turn, associated with lower levels of executive function abilities. As such, the study suggests that one way in which poverty affects executive function is through parenting, which leads to increased stress in the children.

Early education: can cortisol measures help in evaluations?
The study has implications for those looking to identify and intervene with high-risk children in order to improve their executive functioning and, by extension, their school readiness. Blair and his colleagues highlight successful early childhood programs such as Abecedarian and Perry Preschool. Both of these programs have improved the life chances of disadvantaged children through the promotion of self-regulation, which is one aspect of executive functioning. So too have a number of parenting programs, such as the Play and Learning Strategies ("PALS") curriculum.

Blair and colleagues argue that adding measures of stress physiology, such as salivary cortisol, to randomized controlled trials of early childhood interventions would further prove the value of these programs. The authors say, “The inclusion of measures of stress physiology and multiple aspects of self-regulation in future evaluations of similar early care and education programs can help to further establish the point that such programs are highly effective at promoting optimal outcomes for children at risk and represent an efficient and cost-effective social policy response to persistent and pervasive threats to healthy child development associated with the conditions of poverty.”

Reference:
Blair, C., Granger, D.A., Willoughby, M., Mills-Koonce, R., Cox, M., Greenberg, M.T., Kivlighan, K.T., & Fortunato, C. (2011). Salivary cortisol mediates effects of poverty and parenting on executive functions in early childhood. Child Development, forthcoming. DOI: 10.1111/j.1467-8624.2011.01643.x