Science Watch

Preschool has never been more popular. In his 2013 State of the Union address, President Obama introduced a plan to provide universal preschool for all 4-year-olds from low-income and moderate-income families. During his successful run for New York City mayor last year, Bill de Blasio made universal preschool a cornerstone of his campaign.

Even before those proposals, preschool was having a heyday. State funding for pre-K more than doubled, from $2.4 billion in 2002 to $5.4 billion in 2010, according to a 2011 report from The Pew Charitable Trusts. In 2000, some 700,000 children in the United States had access to pre-K, compared with 1.3 million in 2011.

But in many ways, the national conversation about early education is just getting started. The top question about universal pre-K — whether it is worth the cost to taxpayers — remains up for debate. That's partly because studies of early education have found mixed results.

While psychologists have long been involved in studies of preschool, much of the focus lately has focused on economic cost-benefit analyses of early education. But now more than ever, psychologists are crucial in helping to explain how, why, when and for whom some preschool investments work while others fall flat. Though plenty of questions remain, these early-education researchers are adding important shades of gray to the conversation.

"Whether universal pre-K is a good idea is a political question," says Daniel Willingham, PhD, a psychologist at the University of Virginia. "The scientific question would be: Is it likely that you could construct pre-K programs that would benefit kids academically and socially? And I think the answer is yes."

The long view

When politicians discuss the benefits of early education, they often point to two influential long-term studies: The Abecedarian Project and the Perry Preschool Project.

The Abecedarian Project, led by psychologists at the University of North Carolina at Chapel Hill, targeted children from low-income, mostly African-American families in North Carolina. Between 1972 and 1977, investigators randomly assigned four cohorts of infants to an intensive, full-time early-education program from birth to age 5, or to a control group that didn't receive services. Then the researchers followed the children into adulthood.

The investigators found that children who participated in the program scored higher on tests of cognitive functioning from toddlerhood through early adulthood. They had greater academic achievement from the primary grades though young adulthood, and were more likely to go to college.

The Perry Preschool Project had a similar design, but quite different findings. It began in 1962, when David P. Weikart, PhD, a psychologist for the Ypsilanti, Mich., school district, and colleagues randomly assigned low-income African-American children to an intensive two-year preschool program or to a control group that didn't attend preschool. The researchers followed those participants into their 40s.

Initially, the results didn't seem promising. Although children who attended the program scored higher on intelligence tests than the control group right after preschool, those intelligence gains disappeared by elementary school. However, other benefits materialized in early adulthood. The program appeared to have positive effects on high-school graduation rates, adult earnings and crime reduction.

The Perry study seemed to support a view first championed by Nobel laureate and economist James Heckman, PhD: The short-term cognitive benefits of preschool may fade, but long-term social benefits may sprout later in life.

Other studies support the idea that some social benefits persist even as cognitive gains disappear, says C. Cybele Raver, PhD, a psychologist and vice provost of academic, faculty and research affairs at New York University. "I think the field is starting to shift, offering confirmation of some of the points that Heckman has raised. Investments in early childhood reap rewards along the line, in ways that we're just now really understanding."

Not everyone agrees. "The Perry study is a thin reed on which to develop an all-encompassing theory of early intervention," says Grover J. "Russ" Whitehurst, PhD, a child psychologist with the Brookings Institution and former director of the Institute of Education Sciences at the U.S. Department of Education. When it comes to the long-term benefits of early education, he adds, "I think the evidence is mixed."

Mixed messages

Though Abecedarian and Perry have been influential, they have limitations. Both projects were intensive and expensive, making them unlikely models for universal programs in an era of lean education budgets. They also began half a century ago and don't fully reflect our modern knowledge of developmental psychology and education.

Today, researchers are building on what is known about the benefits of early education. In a recent meta-analysis, Greg Duncan, PhD, at the University of California, Irvine, and Katherine Magnuson, PhD, at the University of Wisconsin-Madison, looked across 84 studies of preschool programs conducted from 1965 to 2007. They concluded that early education produced gains in children's language, reading and math skills, equal to about a third of a year of extra learning (Journal of Economic Perspectives, 2013).

Another review by Hirokazu Yoshikawa, PhD, of New York University, and colleagues also concluded that large-scale public preschools can have a substantial positive influence on children's learning, according to the 2013 report Investing in our Future: The Evidence Base on Preschool Education, from the Society for Research in Child Development. Among other examples, the researchers point to recent studies of urban pre-K programs in Tulsa, Okla., and Boston, where children gained between half of a year and a full year in language, literacy and math skills. The gains seemed strongest among children from low-income families.

But other studies have raised concerns about the return on investment of such programs. Head Start, the federal program that promotes school readiness for low-income children under age 5, for example, has shown minimal academic benefits. In addition to early-education services, the program provides health, nutrition and social services to families in need. A report released in December by the U.S. Department of Health and Human Services concluded that third-graders who attended the program as 3- and 4-year-olds showed no clear benefits in cognitive or social-emotional development compared with students who didn't attend Head Start.

"That doesn't suggest to me that the public investment is a slam-dunk by any means," says Whitehurst, who recently expressed similar reservations in congressional testimony to the House Committee on Education and the Workforce.

Some argue that the benefits of Head Start may show up later in life, as Heckman posited. Indeed, in their 2013 review, Yoshikawa and colleagues reported that some longer-term studies of Head Start have found more distant benefits, including more years of schooling, higher earnings and better health. Also, the program might benefit some kids more than others. Researchers at the University of California, Irvine, recently found that children whose mothers spent less time on "preacademic skills" — such as helping their kids recognize letters and count — got a bigger boost in math and literacy skills from Head Start compared to kids who spent more time on such skills at home (Child Development, 2014).

In any case, Willingham notes, Head Start doesn't necessarily belong in the same category with other preschool programs. "It traditionally has more modest goals: to give kids a safe place to go, and socialization with other kids," he says.

Certainly, social learning remains a valuable part of early education, Raver says. Researchers often discuss the cognitive and social-emotional benefits of early education as though they are two competing concepts, but the two domains are actually difficult to disentangle, she says. When a preschool supports cognitive development, children are more likely to feel engaged and build social relationships with their teachers and peers. Investing in their ability to regulate their emotions and attention, on the other hand, is likely to have cognitive and academic payoffs.

Raver and her colleagues demonstrated this with an intervention called the Chicago School Readiness Project in Head Start classrooms. The intervention aimed to improve children's emotional and behavioral regulation — and did — but also increased their vocabularies, letter recognition and math skills (Child Development, 2011). "With a moderate amount of investment, we saw a big gain in kids' behavioral and emotional health [and] in their academic achievement," Raver says.

Defining quality

The mixed findings on early education may be frustrating for policymakers, but in many ways they're not surprising. After all, preschool education programs vary dramatically in all sorts of ways, from class size and length of the school day to teacher education and program curricula.

"Every policymaker says we want a high-quality program," says Robert Pianta, PhD, a psychologist and dean of the Curry School of Education at the University of Virginia. The big question is: What's high quality?

Policymakers tend to focus on structural features such as curriculum or teacher training, Pianta says. "Those become proxies for what kids are experiencing in classrooms. But those structural features don't really capture the features of programs that actually [affect] children's learning and development."

To move beyond those proxies, Pianta and his colleagues developed a system known as the Classroom Assessment Scoring System™ (CLASS) for evaluating teacher-student interactions. This system measures such classroom elements as how well a teacher tunes into behavioral cues (whether a child is losing interest in a classroom activity, say) as well as a teacher's conversational style (whether he or she asks for one-word answers or engages students in more complex dialogue, for example). "You can score those things in a fairly standard way," Pianta says.

He and his colleagues have compared their system with more typical structural indicators of quality, such as student-teacher ratios and teacher qualifications. They found that the quality of student-teacher interactions, as measured by CLASS, was a better predictor of how much kids learned (Science, 2013).

"When the qualities of interactions improve, we see very consistent benefits to the development of children's self-regulation skills and language behaviors, and to vocabulary and literacy skills when those are part of the curriculum," Pianta says. "Those benefits can last into kindergarten and, under some circumstances, beyond."

Of course, those high-quality interactions don't come naturally to every educator. "Teachers have to be good detectors of children's cues, and that's a very hard thing to do when you're in a classroom with 20 kids and all that information is flowing at you at once," Pianta says. Luckily, those cue-detection tactics can be taught.

Pianta and his colleagues have designed professional development programs to help teachers learn the skills that translate to better outcomes for kids. In a randomized study, they showed that teachers who took their 14-week course were more likely to use strategies that promoted kids' higher-order thinking. Those are the strategies that can have an effect on children's early literacy, language and cognitive development (American Educational Research Journal, 2012).

The CLASS system is just one example of the ways in which emerging science can shape preschool programs that actually benefit students. "There's clear room for continued improvement along the lines of bolstering quality and bolstering educational intensity," Pianta says. "I think the glass is absolutely half full, but there's a ways to go."

There's also progress to be made when it comes to understanding the impact of educational policy. For example, economic models may point to an optimal class size for high-quality pre-K. But psychology researchers can help explain which behaviors and interactions are affected when the student-teacher ratio grows or shrinks. "If you just make changes economically, it won't be a surprise to me if you don't have a big impact," Raver says.

Psychological research is certainly needed, agrees Stephanie Curenton, PhD, a developmental and community psychologist at Rutgers University and a fellow of the National Institute for Early Education Research. Yet this debate isn't just about dollar signs and student ID numbers. Before she became a psychologist, Curenton was a preschool teacher. And before that, she was a little girl enrolled in two years of Head Start.

"We look at these programs under the microscope and focus on averages. That's meaningful, and as a scientist I view the world that way a lot," she says. "But we also have to understand that there are real, living people affected by these programs. Sometimes that gets lost in the mix."

Further reading

  • Society for Research in Child Development and Foundation for Child Development. (2013, October). Yoshikawa, H., Weiland, C., Brooks-Gunn, J. Burchinal, M.R., Espinosa, L., Gormley, W.,…Zaslow, M.J. Investing in our future: The evidence base on preschool education.
  • The Pew Center of the States. (2011, September). Transforming public education: Pathway to a pre-K-12 future. Retrieved from
  • U.S. Department of Health and Human Services. (2012, October). Third grade follow-up to the Head Start Impact Study: Final report (OPRE Report 2012-45). Retrieved from