DOES PRESCHOOL MATTER?
Lehrer is a contributing editor at Wired
and the author of Imagine, How We Decide and Proust Was
many kids, the most important years of schooling come before
they can even read. Consider the groundbreaking work of the
Nobel Prize-winning economist James Heckman, who has repeatedly
documented the power of early childhood education. One of his
best case studies is the Perry Preschool Experiment, which looked
at 123 low-income African-American children from Yspilanti,
Michigan. (All the children had IQ scores between 75 and 85).
When the children were three years old, they were randomly assigned
to either a treatment group, and given a high-quality preschool
education, or to a control group, which received no preschool
education at all. The subjects were then tracked over the ensuing
decades, with the most recent analysis comparing the groups
at the age of 40. The differences, even decades after the intervention,
were stark: Adults assigned to the preschool program were 20
percent more likely to have graduated from high school and 19
percent less likely to have been arrested more than five times.
They got much better grades, were more likely to remain married
and were less dependent on welfare programs. This is why, according
to Heckman and colleagues, every dollar invested in preschool
for at-risk children reaps somewhere between eight and nine
dollars in return.
is preschool so important? The answer is obvious: The young
mind is wonderfully malleable, able to develop new habits with
relative ease. Furthermore, the benefits of preschool are not
equally distributed. Rather, they seem to be particularly essential
for those kids from the most disadvantaged households. A new
paper in Psychological Science by Elliot Tucker-Drob,
a psychologist at the University of Texas (Austin), helps explain
why this is the case. He wanted to tease out the relative contributions
of nature and nurture, genes and environment, in the improvement
of academic skills during pre-kindergarten education. His data
set made these questions possible: Tucker-Drob used a national
sample of 1,200 identical and fraternal twins born to 600 families
of various incomes and ethnicities across the United States
in 2001. Because he was comparing identical twins, who share
100 percent of their genes, and fraternal twins, who share 50
percent, he was able to calculate the relative genetic and environmental
influences on achievement at age five, both for those kids who
had been enrolled in preschool and those who went without.
main finding might, at first glance, seem somewhat paradoxical.
According to the twin data, family environmental factors —
the nurture side of the equation — accounted for about
70 percent of the variance in test scores for children who did
not attend preschool. In contrast, those same family factors
only accounted for about 45 percent of variance among children
who attended preschool.
can preschool alter the relative contribution of nature and
nurture? And why does pre-k education make genetics more important?
The answer has to do with the constraints on mental development.
When kids are denied an enriched environment, when they grow
up in a stressed home without lots of books or conversation,
this lack of nurture holds back their nature. As a result, the
children are unable to reach their full genetic potential. (Razib
Khan says it best: “When you remove the environmental
variance, the genetic variance remains.”) The gift of
preschool, then, is that closes the yawning gap between the
life experiences of wealthy and poor toddlers, thus making whatever
differences remain more important.
effect was clearly demonstrated by the standardized test data,
as Tucker-Drob looked at changes in scores correlated with preschool.
Not surprisingly, he found that preschool significantly closed
the achievement gap between rich and poor kids. However, this
winnowing of the gap was entirely due to the raised scores among
those from disadvantaged homes.
these kids were already receiving plenty of cognitive stimulation
at home, it didn’t really matter if they were also stimulated
at school. It’s as if their brains were already maxed
latest study builds on previous work by Tucker-Drob showing
that the impact of parents, at least relative to genetics, largely
depends on socioeconomic status. Last year, he looked at 750
pairs of American twins who were given a test of mental ability
at the age of 10 months and then again at the age of 2. As in
this latest study, Tucker-Drob used twin data to tease apart
the importance of nature and nurture at various points along
the socioeconomic continuum. The first thing he found is that,
when it came to the mental ability of 10-month-olds, the home
environment was the key variable, across every socioeconomic
class. This shouldn’t be too surprising: Most babies are
housebound, their lives dictated by the choices of their parents.
for the 2-year-olds, however, were dramatically different. In
children from poorer households, the decisions of parents still
mattered. In fact, the researchers estimated that the home environment
accounted for approximately 80 percent of the individual variance
in mental ability among poor 2-year-olds. The effect of genetics
opposite pattern appeared in 2-year-olds from wealthy households.
For these kids, genetics primarily determined performance, accounting
for 50 percent of all variation in mental ability. For parents,
then, the correlation appears to be clear: As wealth increases,
the choices of adults play a much smaller role in determining
the mental ability of their children.
are two lessons here. The first lesson is that upper-class parents
worry too much. Although adults tend to fret over the details
of parenting — Is it better to play the piano or the violin?
Should I be a Tiger mom or a Parisian mom? What are the long-term
effects of sleep training? — these details are mostly
insignificant. In the long run, the gift of money is that it
gives a child constant access to a world of stimulation and
enrichment, thus allowing her to fulfill her genetic potential.
The greatest luxury we can give our children, it turns out,
is the luxury of being the type of parent that doesn’t
matter at all.
second lesson is that stunning developmental inequalities set
in almost immediately. As Tucker-Drob demonstrates, even the
mental ability of 2-year-olds can be profoundly affected by
the socioeconomic status of their parents. The end result is
that their potential is held back.
this is why we need good preschools. They are not a panacea,
and their impact varies depending on quality, but early childhood
education is still an essential first step toward eliminating
the achievement gap. Life is unfair; some kids will always be
born into households that have much less. Nevertheless, we have
a duty to ensure that every child has a chance to learn what
he’s capable of.