All anecdotes aside, what are the large-scale long-term effects of preschool? While prior research has shown a "fade-out effect", where early testing gains fade by junior and high school, recent research looking at adults suggests there may in fact be long-lasting effects of preschool. 

We just may have been measuring the wrong things.

Preschool Pays

Most of the studies assessing the effects of early education on later "success" have measured success by using standardized measures of cognitive ability. However, this might be misguided. A recent article in the New York Times ("The Case for $320,000 Kindergarten Teachers") reports on a study conducted by the economist Raj Chetty and his colleagues (it's not peer-reviewed yet, but here's a link to their recent presentation in Cambridge, Massachusetts). They looked at the life trajectories of nearly 12,000 children who were part of a large-scale education program in the 80's called Project Star which was based in Tennessee. Like earlier studies, they found the drop-out effect: the effect of good teaching, as measured by test scores, almost completely disappeared by junior high.

A different story was found when they looked at the group who participated in the experiment as adults (age 30). Those adults who did better in preschool were more likely to go to college, were less likely to be single parents, and were more likely to save for retirement than those with similar backgrounds who did not do as well in preschool. Teaching quality turned out to be a particularly important factor in preschool performance. Factors such as class size and the socioeconomic status of peers had an effect on preschool performance, but neither of these factors explained differences in preschool performance as much as good teaching.

The group that did better in preschool also earned an extra $100 a year at age 27 for every percentile increase in preschool test-score performance. According to the New York Times article,

"A student who went from average to the 60th percentile - typical jump for a 5-year-old with a good teacher - could expect to make $1,000 more a year at age 27 than a student who remained at the average. Over time, the effect seems to grow, too."

One of the authors of the study, Emmanuel Saez, estimates that a terrific kindergarten teacher is worth about $320,000 a year, if you consider the additional monetary value a full class of students with a good preschool teacher can expect to earn throughout their careers. There are of course also social gains as well, such as increased socio-economic status, better health, and less crime.

Over at the always insightful blog "Frontal Cortex", Jonah Lehrer talks about a recent paper ("Investing in Our Young People") written by two top economists- Flavio Cunha and James Heckman- where they review a number of studies showing the long-term effects of childhood education.

One of the studies included in that review which Leher talks about on his blog is the Perry Preschool Experiment, which randomly assigned 123 low income African-American children from Michigan to either a quality preschool education group or a control group that received no early education.The Perry Preschool Experiment found the usual fade-out effect, with the initial bump in IQ disapearing by second grade. However, following up the groups when they were 40 years old, they found that the batch who received quality preschool education were much more likely to graduate high school and remain married, and less likely to be on welfare many years later than the control group. According to an article in the University of Chicago's Chronicle, the program can be expected to yield $8.70 for every single dollar invested in each participant. Sixty-five percent of that return comes from reduced levels of crime alone.

Clearly, good pre-school has a long-lasting effect on adult's economic success, and has other important social effects, even if it's not demonstrating long-lasting test score success. This of course begs the question:

What's going on here?

If preschool isn't boosting intelligence, what is it boosting that has such an enduring effect? Or, as Lehrer puts it, "How does preschool work its magic?"

Leher agrees with Cunha and Heckman that preschool may help develop important non-cognitive skills, such as increased self-control and persistence. According to Leher,

"Preschool might not make us smarter - our intelligence is strongly shaped by our genes - but it can make us a better person, and that's even more important."

I like this sentiment. But I'm not quite clear what exactly it means to be a "better person". So I thought I'd see what Heckman has to say.

According to Heckman and co-editor Alan Krueger in an upcoming book called "Inequality in America: What Role for Human Capital Policies?",

"The greatest effect of early childhood programs is on non-cognitive skills, motivation and achievement, not on IQ."

OK, so we're talking about the capacity for hard work and practice. They also note that

"Numerous instances can be cited of people with high IQs who fail to achieve success in life because they lacked self-discipline and of people with low IQs who succeeded by virtue of persistence, reliability and  self-discipline."

I'm with them, I really am. But here's a statement I want to explore a bit:

"Our analysis challenged the conventional point of view that equates skill with intelligence, and draws on a body of research that demonstrates the importance of both cognitive and non-cognitive skills in determining socioeconomic success."

I wonder, can we really so neatly separate cognitive from non-cognitive abilities?

Cognitive vs. Non-Cognitive Abilities

As one astute commentator ("kmarxha") on Leher's blog notes,

"I would argue that skills of self-regulation are cognitive as they are connected to executive function. We cannot use the information in our brain if we do not have executive function (working memory, inhibitory control, cognitive flexibility)."

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Tags: anecdotes, chetty, cognitive ability, collegues, creativity, different story, early education, education program, executive functions, exploring the new world, french songs, kindergarten teachers, magic, new york times, non-cognitive abilities, petite maison, pre school, pre-school, prior research, project star, recent article, social interactions, test scores, trajectories, wonderful things