Are children’s earliest years the most important for their cognitive development?

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Duncan Webb (master PPD)

An expansive body of evidence that spans economics, biology, and neuroscience now backs up the claim that what happens to children in their early childhood can have large effects on their wellbeing and economic productivity in adulthood (1). Nutrition, exposure to disease, and parental behaviour can all have powerful impacts on children’s cognitive and socioemotional development. These in turn affect individuals’ success in school, the job market, and other areas of life. And such factors may be particularly important in low- and middle-income countries, where children might be more vulnerable to shocks that affect their development if insurance markets and social safety nets aren’t effective. The specific timing of such shocks may be particularly important: the first 1000 days of life is often said to be a “critical period” that is crucial for normal cognitive development. However, there has been little direct comparison in the economics literature of the effects of equivalent shocks or programmes at multiple different ages. This is an important question for policy-makers: it will help them understand the most effective way to target early childhood programmes in order to get the best value for money.

In this article, Duncan Webb tests directly for the existence of critical periods in childhood development using a unique empirical setting. He examines the impact of weather shocks during early childhood on later adult cognitive and socioemotional outcomes for people born in rural Indonesia between 1988 and 2000. The main advantage of the empirical approach used here is that, by using weather shocks, Webb is able to compare the impact of multiple independent shocks across multiple ages. Such an approach is typically not available when examining the effect of an early childhood programme that occurs only once. Moreover, since the data he uses contains a full history of an individual’s migration over their childhood, he can analyse the effects of shocks at every age from in utero all the way up to age 15. His main finding is that there appears to be a strong critical period for these shocks at age 2 for cognitive development, but no similar critical period for socioemotional development. In other words, shocks have a particularly large impact on adult cognitive skills when they occur at age 2. By contrast, measures of adult socioemotional outcomes are either not affected by the shocks, or have an effect that is spread across multiple ages rather than being concentrated in a specific period at age 2.

In order to interpret the policy implications of these results, it is important to understand the mechanisms through which weather shocks may be having an effect on children. To this end, Webb shows evidence that better weather conditions lead to increased household consumption, along with taller and heavier children. This suggests that the shocks may be having an effect through agricultural income and nutritional channels. Arguably, policies that target agricultural income and nutrition may have comparable effects to these shocks. If this is true, then these results imply that policy investments in early childhood will have the highest returns to cognitive development when targeting children aged 2, in line with the notion of a “critical period” seen in neuroscience. On the other hand, concentrating investments in the first 1000 days of life doesn’t yield similarly high benefits when focusing on socioemotional development as an outcome. Policies that are aiming to improve children’s socioemotional skills may therefore be better off spreading investments out over childhood and adolescence. In either case, the fact that weather shocks have such a long-term impact on adult outcomes at all shows that rural Indonesian households are not able to sufficiently smooth consumption and provides further backing for the expansion of social safety nets.

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Reference
(1) Almond, Douglas, Janet Currie, and Valentina Duque. 2018. “Childhood Circumstances and Adult Outcomes: Act II.” Journal of Economic Literature, 56 (4): 1360-1446.

Master’s thesis title: “Critical Periods in Cognitive and Socioemotional Development - Evidence from Weather Shocks in Indonesia”
Under the direction of: Karen Macours
Available at: https://dumas.ccsd.cnrs.fr/dumas-02407565

Photo credit: MC Image (Shutterstock)