Publishing in Science, Gormley et al. compared the benefits of Oklahoma's TPS pre-K program to Head Start. Conclusion: preschool matters in cognitive development.

Early childhood education programs in the United States face enormous challenges. The overwhelming majority of Head Start program participants are poor, and many Head Start children face additional risk factors, such as a single-parent home or a home where English is not the primary language spoken. Pre-K programs targeted to poor or otherwise at-risk children face similar challenges. Even universally available programs, such as Oklahoma's, must cope with the realities of poor families, fragmented families, and immigrant families.

Against this backdrop, it is instructive to compare the potency of program participation variables with that of other variables in our statistical models. For the TPS model, program participation is a more powerful predictor of prereading and prewriting test score outcomes than gender, race and/or ethnicity, free lunch eligibility, mother's education, or whether the biological father lives at home... For the Head Start model, program participation is a more powerful predictor of premath outcomes than gender, free lunch eligibility, mother's education, or whether the biological father lives at home... Early childhood education can therefore make a big difference for short-term test scores, substantially muting the negative effects of family and environmental risk factors.

Though the effectiveness of the two programs vary -- TPS is more effective according to two measures -- the benefits of both are clear.

This article reminded me of a working paper by James Heckman about the merits of getting kids when they are young. The article is a bit long, but here are some of his bullet points:

9. Experimental evidence on the positive effects of early interventions on children in disadvantaged families is consistent with a large body of non-experimental evidence showing that the absence of supportive family environments harms child outcomes.

10. If society intervenes early enough, it can improve cognitive and socioemotional abilities and the health of disadvantaged children.

11. Early interventions promote schooling, reduce crime, foster workforce productivity and reduce teenage pregnancy.

12. These interventions are estimated to have high benefit-cost ratios and rates of return.

13. As programs are currently congured, interventions early in the life cycle of disadvantaged children have much higher economic returns than later interventions such as reduced pupil-teacher ratios, public job training, convict rehabilitation programs, adult literacy programs, tuition subsidies or expenditure on police.

14. Life cycle skill formation is dynamic in nature. Skill begets skill; motivation begets motivation. Motivation cross-fosters skill and skill cross-fosters motivation. If a child is not motivated to learn and engage early on in life, the more likely it is that when the child becomes an adult, it will fail in social and economic life. The longer society waits to intervene in the life cycle of a disadvantaged child, the more costly it is to remediate disadvantage. (Emphasis mine.)

Heckman goes on to summarize the substantial body of evidence that our place in life is not God-given or genetic in origin. Substantial improvements in people's lives can occur through training.

On the other hand, I am more than willing to acknowledge that there is also evidence that psychological traits like executive function are highly heritable.

To this data, I have two responses. First, even psychological traits that are highly heritable traits are susceptible to gene-environment interactions.

You could take the often used height example. Height is heritable, but people in the US are taller than people in the third world. What is the difference? There is a permissive environment -- probably having to do with better nutrition -- in the US that allows for the greater average height, even on a background of heritability. You could apply this analogy to preschool and performance. Yes, psychological traits necessary for good performance may be highly heritable. On the other hand, the best expression of those traits may only occur in a permissive environment that includes childhood education.

Second, nailing down exactly what psychological traits are necessary for success is a difficult business. The "right stuff" for success in life is not just executive function -- although that is probably part of it. It includes the ability to get along with people and solve complex and ambiguous problems. Whether our psychological batteries accurately capture these abilities is an open question. Furthermore, some authors have argued that concepts like g-factor or IQ are basically bunk to begin with and artifacts of factors analysis. (Read this post for more.)

The debate between nature and nurture with respect to these issues is likely to go on in perpetuity. In any case, I like Heckman's paper because he uses the cost-benefit approach in analyzing policies intended to improve student performance. If we really want to get the bang for our buck, we need to start as young as possible.

Hat-tip: Greg Mankiw