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.
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for $320,000 Kindergarten Teachers") reports on a study conducted by the economist Raj Chetty and his colleagues (it's not peer-reviewed yet, but here's a link to their recent presentation in Cambridge, Massachusetts).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)."
This is a great point! Human executive functions, which tend to be located in the prefrontal cortex of the brain, help us attain our long-term goals by enabling us to stay on task, resist distractions, inhibit immediate rewards in the service of longer-term rewards, be mentally flexible, and regulate our emotions.
The reality of the matter is that many things, both dispositional (personality, mood, etc.) and situational (high stress situations, harsh and unpredictable environments) can affect our "executive functioning", and the state of our executive functioning can have a significant impact on many real-life tasks, not to mention cognitive tests.
As that insightful commentator noted, there are actually multiple executive functions. These include the ability to keep representations active in working memory while resisting distractions, the ability to inhibit prepotent responses, and the ability to be flexible and switch between different modes of thinking depending on the situation. All of these executive functions are adaptive in the real-world and can explain real-world performance above and beyond measured "intelligence" (see Blair, 2006 for more on executive functions, emotional self-regulation, and ways "fluid cognition" can be separated from "general intelligence").
In fact, not all executive functions may be equally related to IQ. Friedman et al. (2006) found that while related, executive functions are not unitary, and only the ability to update working memory was related to conventional intelligence measures. Inhibition and task shifting were not related to IQ (but see the recent article by Floyd et al. for a different perspective, showing how executive functions map onto a general intelligence factor as well as various components of intelligence).
Also, various researchers have noted that the constructs "general intelligence", "fluid intelligence", "executive function", and "working memory" aren't the same things, either behaviorally or in the brain (Blair, 2006; Garlick & Sejnowski, 2006; Heitz et al., 2006; Kane & Engle, 2002). Clearly, there is still a lot of work to be done in clarifying these different constructs and minimizing potential redundancies.
Nevertheless, the potential separation of certain executive functions (e.g., inhibiting and shifting) from working memory and IQ doesn't make these "other" executive functions any less "cognitive". And these other executive functions may play just as an important role in enabling the persistence, grit, motivation, and emotional regulation skills that are related to real-world functioning (see Blair, 2006).
To move things forward, I think we need more research that deterimes the precise cognitive mechanisms that allow people to reach their long-term goals, and the factors in preschool that may be boosting those skills. This is not to reduce the importance of the cognitive skills measured by IQ tests, including working memory (IQ and working memory both predict a substantial portion of differences in various educational, job, and societal outcomes). I just think we need to more clearly define what these so-called "non-cognitive" abilities are and understand how many different factors (both internal and external to the individual) can influence the cognitive skills necessary to operate in the real world.
This doesn't mean that once we find out what these mechanisms are, it's going to be easy to change them. In a recent study by Thorell et al. called "Training and transfer effects of executive functions in preschool children", preschool children who were trained in working memory showed significant improvements, whereas those trained to increase the "inhibition" executive function didn't show an improvement.
On the one hand, this is good news: working memory can be increased! There is in fact a lot of recent research showing the trainability of working memory (see a recent review in Trends in Cognitive Science by Torkel Klingberg called "Training and plasticity of working memory").
But on the other hand... there's a small elephant in the room here. If it is indeed true that the other executive functions (inhibition and mental flexibility) are difficult to train, and it is these abilities that are importantly related to the so-called "non-cognitive" traits such as persistence, motivation, grit, and emotional regulation, then perhaps these "non-cognitive" abilities could be less easy to train than conventional intelligence-type abilities. So there's clearly more work to be done. I remain open to every possibility. In fact, I'm even open to the possibility that I have it completely backwards!
Maybe it's the lack
of executive functions in preschool that proves the advantage. In a recent article in Current Directions in Psychological Science
called "Cognition Without Control: When a Little Frontal Lobe Goes a Long Way
", Sharon L. Thompson-Schill
and her colleagues argue that while "the prefrontal cortex is crucial for the ability to regulate thought and behavior", the fact that young children don't have a fully formed prefrontal cortex may, on balance, be advantageous, with the positive consequences of that developmental trajectory outweighing the negative. They provide some nice examples of how cognitive control can impede lots of real-life learning and how the slow development of the prefrontal cortex may be an evolutionary adaptation that allows children to learn about the social world and learn linguistic conventions. They explore the implications of the late development of executive control for ADHD
spectrum disorders, creativity
, and sleep
So maybe the thing that really separates preschool from the rest of schooling is the spontaneity and openness to experience that comes from not having fully developed executive functions yet, and good preschool teachers are good at getting children to open their minds, so to speak.
Well, whatever is going on, there clearly is something going on in preschool, independent of the kinds of skills that are measured by standardized tests, that is having such long-lasting effects.
I can personally attest to this "something-other-than-IQ" effect: I did abysmally on tests when I was young (IQ tests and school tests), and was sent to a "special" school for students with learning disabilities (although, ironically, that school environment more resembled my preschool and I was very dissapointed when I had to return to public school after one year). Yet I somehow ended up with a Ph.D. from Yale, where I was a pre-doctoral fellow at the Edward Zigler Center in Child Development and Social Policy and where I learned about the many long-lasting "non-cogntive" effects of the Head Start program. Clearly, other cognitive skills allowed me to navigate all that knowledge and come up with new ideas in graduate school.
But we don't just have to stick with anecdote. The exciting thing is that there is now appearing to be a better appreciation of the important long-term effects of preschool that extend beyond test scores as the outcome measure. This opens up many exciting possibilities for understanding what's so special about preschool.
When I think back to my pre-school years, I think about all the different experiences I engaged in with my preschool peers. There was this spirit of mutual discovery, learning, and adventure. Even among all the social interactions, I was encouraged to ask questions, think for myself, and determine on my own which experiences I resonated with and which ones I might not want to pursue further in life.
Perhaps it's difficult for test makers to capture the subjective joys and life-long skills preschool promotes. But as researchers living in a society that values creativity and innovation, it seems worth a try.
© 2010 by Scott Barry Kaufman
(Note: Thanks to Joshua Aronson for bringing the New York Times article to my attention.)
Blair, C. (2006). How similar are fluid cognition and general intelligence? A developmental neuroscience perspective on fluid cognition as an aspect of human cognitive ability. Behavioral and Brain Sciences, 29, 109-125.
Floyd, R.G., Bergeron, R., Hamilton, G., & Parra, G.R. (2010). Do executive functions fir with the Cattell-Horn-Carroll model? Evidence from a joint factor analysis of the Delis-Kaplan executive function system and the Woodcock-Johnson III tests of cognitive abilities. Psychology in the Schools, 47, 721-738.
Friedman, N.P., Miyake, A., Corley, R.P., Young, S.E., DeFries, J.C., & Hewitt, J.K. (2006). Not all executive functions are related to intelligence. Psychological Science, 17, 172-179.
Garlick, D., & Sejnowski, T.J. (2006). There is more to fluid intelligence than working memory capacity and executive function. Behavior and Brain Sciences, 29, 134-135.
Heitz, R. P., Redick, T. S., Hambrick, D. Z., Kane, M. J., Conway, A. R. A., & Engle, R. W. (2006). WM, EF, and gF are not the same. Behavioral and Brain Sciences, 29, 135-136.
Kane, M.J., & Engle, R.W. (2002). The role of prefrontal cortex in working-memory capacity, executive attention, and general fluid intelligence: An individual-differences perspective. Psychonomic Bulletin & Review, 9, 637-671.
Klingberg, T. (2010). Training and plasticity of working memory.Trends in Cognitive Sciences, 14, 317-324.
Thompson-Schill, S.L., Ramscar, M., & Chrysikou, E.G. (2009). Cognition without control: When a little frontal lobe goes a long way. Current Directions in Psychology Science, 18, 259-263.
Thorell, L.B., Lindqvist, S., Bergman, S., Bohlin, G., & Klingberg, T. (2008). Training and transfer effects of executive functions in preschool children. Developmental Science, 11, 969-976.