Cognitive Development

Choose one of the following articles: that is attached 

• Contributions of Neuroscience to Our Understanding of Cognitive Development
• Don’t! The Secret of Self-Control

Provide an in-depth analysis of the selected article and respond to the following:

• Write a summary.
• Describe the main points of the article and how it relates to the week’s course and text readings.
• Evaluate the article on the basis of your own thoughts and perspectives on the topic covered.

Submission Details:

• Support your responses with examples.
• Cite any sources in APA format.

DON’T!

Lehrer, Jonah . The New Yorker ; New York  Vol. 85, Iss. 14,  (May 18, 2009): 26.

ProQuest document link

ABSTRACT
Columbia psychology professor Walter Mischel is profiled. In the 1960’s, Mischel and colleagues performed an

experiment designed to explore why some children are able to delay gratification and others can’t. Now subjects

from that experiment are being asked to return for functional MRI studies, in the hope that the neurology of self-

control may be mapped.

FULL TEXT
 

In the late nineteen-sixties, Carolyn Weisz, a four-year-old with long brown hair, was invited into a “game room” at

the Bing Nursery School, on the campus of Stanford University. The room was little more than a large closet,

containing a desk and a chair. Carolyn was asked to sit down in the chair and pick a treat from a tray of

marshmallows, cookies, and pretzel sticks. Carolyn chose the marshmallow. Although she’s now forty-four, Carolyn

still has a weakness for those air-puffed balls of corn syrup and gelatine. “I know I shouldn’t like them,” she says.

“But they’re just so delicious!” A researcher then made Carolyn an offer: she could either eat one marshmallow

right away or, if she was willing to wait while he stepped out for a few minutes, she could have two marshmallows

when he returned. He said that if she rang a bell on the desk while he was away he would come running back, and

she could eat one marshmallow but would forfeit the second. Then he left the room.

Although Carolyn has no direct memory of the experiment, and the scientists would not release any information

about the subjects, she strongly suspects that she was able to delay gratification. “I’ve always been really good at

waiting,” Carolyn told me. “If you give me a challenge or a task, then I’m going to find a way to do it, even if it means

not eating my favorite food.” Her mother, Karen Sortino, is still more certain: “Even as a young kid, Carolyn was very

patient. I’m sure she would have waited.” But her brother Craig, who also took part in the experiment, displayed less

fortitude. Craig, a year older than Carolyn, still remembers the torment of trying to wait. “At a certain point, it must

have occurred to me that I was all by myself,” he recalls. “And so I just started taking all the candy.” According to

Craig, he was also tested with little plastic toys–he could have a second one if he held out–and he broke into the

desk, where he figured there would be additional toys. “I took everything I could,” he says. “I cleaned them out.

After that, I noticed the teachers encouraged me to not go into the experiment room anymore.”

Footage of these experiments, which were conducted over several years, is poignant, as the kids struggle to delay

gratification for just a little bit longer. Some cover their eyes with their hands or turn around so that they can’t see

the tray. Others start kicking the desk, or tug on their pigtails, or stroke the marshmallow as if it were a tiny stuffed

animal. One child, a boy with neatly parted hair, looks carefully around the room to make sure that nobody can see

him. Then he picks up an Oreo, delicately twists it apart, and licks off the white cream filling before returning the

cookie to the tray, a satisfied look on his face.

Most of the children were like Craig. They struggled to resist the treat and held out for an average of less than

three minutes. “A few kids ate the marshmallow right away,” Walter Mischel, the Stanford professor of psychology

in charge of the experiment, remembers. “They didn’t even bother ringing the bell. Other kids would stare directly at

the marshmallow and then ring the bell thirty seconds later.” About thirty per cent of the children, however, were

like Carolyn. They successfully delayed gratification until the researcher returned, some fifteen minutes later.

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These kids wrestled with temptation but found a way to resist.

The initial goal of the experiment was to identify the mental processes that allowed some people to delay

gratification while others simply surrendered. After publishing a few papers on the Bing studies in the early

seventies, Mischel moved on to other areas of personality research. “There are only so many things you can do

with kids trying not to eat marshmallows.”

But occasionally Mischel would ask his three daughters, all of whom attended the Bing, about their friends from

nursery school. “It was really just idle dinnertime conversation,” he says. “I’d ask them, ‘How’s Jane? How’s Eric?

How are they doing in school?’ ” Mischel began to notice a link between the children’s academic performance as

teen-agers and their ability to wait for the second marshmallow. He asked his daughters to assess their friends

academically on a scale of zero to five. Comparing these ratings with the original data set, he saw a correlation.

“That’s when I realized I had to do this seriously,” he says. Starting in 1981, Mischel sent out a questionnaire to all

the reachable parents, teachers, and academic advisers of the six hundred and fifty-three subjects who had

participated in the marshmallow task, who were by then in high school. He asked about every trait he could think

of, from their capacity to plan and think ahead to their ability to “cope well with problems” and get along with their

peers. He also requested their S.A.T. scores.

Once Mischel began analyzing the results, he noticed that low delayers, the children who rang the bell quickly,

seemed more likely to have behavioral problems, both in school and at home. They got lower S.A.T. scores. They

struggled in stressful situations, often had trouble paying attention, and found it difficult to maintain friendships.

The child who could wait fifteen minutes had an S.A.T. score that was, on average, two hundred and ten points

higher than that of the kid who could wait only thirty seconds.

Carolyn Weisz is a textbook example of a high delayer. She attended Stanford as an undergraduate, and got her

Ph.D. in social psychology at Princeton. She’s now an associate psychology professor at the University of Puget

Sound. Craig, meanwhile, moved to Los Angeles and has spent his career doing “all kinds of things” in the

entertainment industry, mostly in production. He’s currently helping to write and produce a film. “Sure, I wish I had

been a more patient person,” Craig says. “Looking back, there are definitely moments when it would have helped

me make better career choices and stuff.”

Mischel and his colleagues continued to track the subjects into their late thirties–Ozlem Ayduk, an assistant

professor of psychology at the University of California at Berkeley, found that low-delaying adults have a

significantly higher body-mass index and are more likely to have had problems with drugs–but it was frustrating to

have to rely on self-reports. “There’s often a gap between what people are willing to tell you and how they behave in

the real world,” he explains. And so, last year, Mischel, who is now a professor at Columbia, and a team of

collaborators began asking the original Bing subjects to travel to Stanford for a few days of experiments in an fMRI

machine. Carolyn says she will be participating in the scanning experiments later this summer; Craig completed a

survey several years ago, but has yet to be invited to Palo Alto. The scientists are hoping to identify the particular

brain regions that allow some people to delay gratification and control their temper. They’re also conducting a

variety of genetic tests, as they search for the hereditary characteristics that influence the ability to wait for a

second marshmallow.

If Mischel and his team succeed, they will have outlined the neural circuitry of self-control. For decades,

psychologists have focussed on raw intelligence as the most important variable when it comes to predicting

success in life. Mischel argues that intelligence is largely at the mercy of self-control: even the smartest kids still

need to do their homework. “What we’re really measuring with the marshmallows isn’t will power or self-control,”

Mischel says. “It’s much more important than that. This task forces kids to find a way to make the situation work

for them. They want the second marshmallow, but how can they get it? We can’t control the world, but we can

control how we think about it.”

Walter Mischel is a slight, elegant man with a shaved head and a face of deep creases. He talks with a Brooklyn

bluster and he tends to act out his sentences, so that when he describes the marshmallow task he takes on the

body language of an impatient four-year-old. “If you want to know why some kids can wait and others can’t, then

you’ve got to think like they think,” Mischel says.

Mischel was born in Vienna, in 1930. His father was a modestly successful businessman with a fondness for cafe

society and Esperanto, while his mother spent many of her days lying on the couch with an ice pack on her

forehead, trying to soothe her frail nerves. The family considered itself fully assimilated, but after the Nazi

annexation of Austria, in 1938, Mischel remembers being taunted in school by the Hitler Youth and watching as his

father, hobbled by childhood polio, was forced to limp through the streets in his pajamas. A few weeks after the

takeover, while the family was burning evidence of their Jewish ancestry in the fireplace, Walter found a long-

forgotten certificate of U.S. citizenship issued to his maternal grandfather decades earlier, thus saving his family.

The family settled in Brooklyn, where Mischel’s parents opened up a five-and-dime. Mischel attended New York

University, studying poetry under Delmore Schwartz and Allen Tate, and taking studio-art classes with Philip

Guston. He also became fascinated by psychoanalysis and new measures of personality, such as the Rorschach

test. “At the time, it seemed like a mental X-ray machine,” he says. “You could solve a person by showing them a

picture.” Although he was pressured to join his uncle’s umbrella business, he ended up pursuing a Ph.D. in clinical

psychology at Ohio State.

But Mischel noticed that academic theories had limited application, and he was struck by the futility of most

personality science. He still flinches at the naivete of graduate students who based their diagnoses on a battery of

meaningless tests. In 1955, Mischel was offered an opportunity to study the “spirit possession” ceremonies of the

Orisha faith in Trinidad, and he leapt at the chance. Although his research was supposed to involve the use of

Rorschach tests to explore the connections between the unconscious and the behavior of people when possessed,

Mischel soon grew interested in a different project. He lived in a part of the island that was evenly split between

people of East Indian and of African descent; he noticed that each group defined the other in broad stereotypes.

“The East Indians would describe the Africans as impulsive hedonists, who were always living for the moment and

never thought about the future,” he says. “The Africans, meanwhile, would say that the East Indians didn’t know

how to live and would stuff money in their mattress and never enjoy themselves.”

Mischel took young children from both ethnic groups and offered them a simple choice: they could have a

miniature chocolate bar right away or, if they waited a few days, they could get a much bigger chocolate bar.

Mischel’s results failed to justify the stereotypes–other variables, such as whether or not the children lived with

their father, turned out to be much more important–but they did get him interested in the question of delayed

gratification. Why did some children wait and not others? What made waiting possible? Unlike the broad traits

supposedly assessed by personality tests, self-control struck Mischel as potentially measurable.

In 1958, Mischel became an assistant professor in the Department of Social Relations at Harvard. One of his first

tasks was to develop a survey course on “personality assessment,” but Mischel quickly concluded that, while

prevailing theories held personality traits to be broadly consistent, the available data didn’t back up this

assumption. Personality, at least as it was then conceived, couldn’t be reliably assessed at all. A few years later, he

was hired as a consultant on a personality assessment initiated by the Peace Corps. Early Peace Corps volunteers

had sparked several embarrassing international incidents–one mailed a postcard on which she expressed disgust

at the sanitary habits of her host country–so the Kennedy Administration wanted a screening process to eliminate

people unsuited for foreign assignments. Volunteers were tested for standard personality traits, and Mischel

compared the results with ratings of how well the volunteers performed in the field. He found no correlation; the

time-consuming tests predicted nothing. At this point, Mischel realized that the problem wasn’t the tests–it was

their premise. Psychologists had spent decades searching for traits that exist independently of circumstance, but

what if personality can’t be separated from context? “It went against the way we’d been thinking about personality

since the four humors and the ancient Greeks,” he says.

While Mischel was beginning to dismantle the methods of his field, the Harvard psychology department was in

tumult. In 1960, the personality psychologist Timothy Leary helped start the Harvard Psilocybin Project, which

consisted mostly of self-experimentation. Mischel remembers graduate students’ desks giving way to mattresses,

and large packages from Ciba chemicals, in Switzerland, arriving in the mail. Mischel had nothing against hippies,

but he wanted modern psychology to be rigorous and empirical. And so, in 1962, Walter Mischel moved to Palo

Alto and went to work at Stanford.

There is something deeply contradictory about Walter Mischel–a psychologist who spent decades critiquing the

validity of personality tests–inventing the marshmallow task, a simple test with impressive predictive power.

Mischel, however, insists there is no contradiction. “I’ve always believed there are consistencies in a person that

can be looked at,” he says. “We just have to look in the right way.” One of Mischel’s classic studies documented the

aggressive behavior of children in a variety of situations at a summer camp in New Hampshire. Most

psychologists assumed that aggression was a stable trait, but Mischel found that children’s responses depended

on the details of the interaction. The same child might consistently lash out when teased by a peer, but readily

submit to adult punishment. Another might react badly to a warning from a counsellor, but play well with his

bunkmates. Aggression was best assessed in terms of what Mischel called “if-then patterns.” If a certain child was

teased by a peer, then he would be aggressive.

One of Mischel’s favorite metaphors for this model of personality, known as interactionism, concerns a car making

a screeching noise. How does a mechanic solve the problem? He begins by trying to identify the specific

conditions that trigger the noise. Is there a screech when the car is accelerating, or when it’s shifting gears, or

turning at slow speeds? Unless the mechanic can give the screech a context, he’ll never find the broken part.

Mischel wanted psychologists to think like mechanics, and look at people’s responses under particular conditions.

The challenge was devising a test that accurately simulated something relevant to the behavior being predicted.

The search for a meaningful test of personality led Mischel to revisit, in 1968, the protocol he’d used on young

children in Trinidad nearly a decade earlier. The experiment seemed especially relevant now that he had three

young daughters of his own. “Young kids are pure id,” Mischel says. “They start off unable to wait for anything–

whatever they want they need. But then, as I watched my own kids, I marvelled at how they gradually learned how

to delay and how that made so many other things possible.”

A few years earlier, in 1966, the Stanford psychology department had established the Bing Nursery School. The

classrooms were designed as working laboratories, with large one-way mirrors that allowed researchers to observe

the children. In February, Jennifer Winters, the assistant director of the school, showed me around the building.

While the Bing is still an active center of research–the children quickly learn to ignore the students scribbling in

notebooks–Winters isn’t sure that Mischel’s marshmallow task could be replicated today. “We recently tried to do a

version of it, and the kids were very excited about having food in the game room,” she says. “There are so many

allergies and peculiar diets today that we don’t do many things with food.”

Mischel perfected his protocol by testing his daughters at the kitchen table. “When you’re investigating will power

in a four-year-old, little things make a big difference,” he says. “How big should the marshmallows be? What kind of

cookies work best?” After several months of patient tinkering, Mischel came up with an experimental design that

closely simulated the difficulty of delayed gratification. In the spring of 1968, he conducted the first trials of his

experiment at the Bing. “I knew we’d designed it well when a few kids wanted to quit as soon as we explained the

conditions to them,” he says. “They knew this was going to be very difficult.”

At the time, psychologists assumed that children’s ability to wait depended on how badly they wanted the

marshmallow. But it soon became obvious that every child craved the extra treat. What, then, determined self-

control? Mischel’s conclusion, based on hundreds of hours of observation, was that the crucial skill was the

“strategic allocation of attention.” Instead of getting obsessed with the marshmallow–the “hot stimulus”–the

patient children distracted themselves by covering their eyes, pretending to play hide-and-seek underneath the

desk, or singing songs from “Sesame Street.” Their desire wasn’t defeated–it was merely forgotten. “If you’re

thinking about the marshmallow and how delicious it is, then you’re going to eat it,” Mischel says. “The key is to

avoid thinking about it in the first place.”

In adults, this skill is often referred to as metacognition, or thinking about thinking, and it’s what allows people to

outsmart their shortcomings. (When Odysseus had himself tied to the ship’s mast, he was using some of the skills

of metacognition: knowing he wouldn’t be able to resist the Sirens’ song, he made it impossible to give in.)

Mischel’s large data set from various studies allowed him to see that children with a more accurate understanding

of the workings of self-control were better able to delay gratification. “What’s interesting about four-year-olds is

that they’re just figuring out the rules of thinking,” Mischel says. “The kids who couldn’t delay would often have the

rules backwards. They would think that the best way to resist the marshmallow is to stare right at it, to keep a

close eye on the goal. But that’s a terrible idea. If you do that, you’re going to ring the bell before I leave the room.”

According to Mischel, this view of will power also helps explain why the marshmallow task is such a powerfully

predictive test. “If you can deal with hot emotions, then you can study for the S.A.T. instead of watching television,”

Mischel says. “And you can save more money for retirement. It’s not just about marshmallows.”

Subsequent work by Mischel and his colleagues found that these differences were observable in subjects as

young as nineteen months. Looking at how toddlers responded when briefly separated from their mothers, they

found that some immediately burst into tears, or clung to the door, but others were able to overcome their anxiety

by distracting themselves, often by playing with toys. When the scientists set the same children the marshmallow

task at the age of five, they found that the kids who had cried also struggled to resist the tempting treat.

The early appearance of the ability to delay suggests that it has a genetic origin, an example of personality at its

most predetermined. Mischel resists such an easy conclusion. “In general, trying to separate nature and nurture

makes about as much sense as trying to separate personality and situation,” he says. “The two influences are

completely interrelated.” For instance, when Mischel gave delay-of-gratification tasks to children from low-income

families in the Bronx, he noticed that their ability to delay was below average, at least compared with that of

children in Palo Alto. “When you grow up poor, you might not practice delay as much,” he says. “And if you don’t

practice then you’ll never figure out how to distract yourself. You won’t develop the best delay strategies, and

those strategies won’t become second nature.” In other words, people learn how to use their mind just as they

learn how to use a computer: through trial and error.

But Mischel has found a shortcut. When he and his colleagues taught children a simple set of mental tricks–such

as pretending that the candy is only a picture, surrounded by an imaginary frame–he dramatically improved their

self-control. The kids who hadn’t been able to wait sixty seconds could now wait fifteen minutes. “All I’ve done is

given them some tips from their mental user manual,” Mischel says. “Once you realize that will power is just a

matter of learning how to control your attention and thoughts, you can really begin to increase it.”

Marc Berman, a lanky graduate student with an easy grin, speaks about his research with the infectious

enthusiasm of a freshman taking his first philosophy class. Berman works in the lab of John Jonides, a

psychologist and neuroscientist at the University of Michigan, who is in charge of the brain-scanning experiments

on the original Bing subjects. He knows that testing forty-year-olds for self-control isn’t a straightforward

proposition. “We can’t give these people marshmallows,” Berman says. “They know they’re part of a long-term

study that looks at delay of gratification, so if you give them an obvious delay task they’ll do their best to resist.

You’ll get a bunch of people who refuse to touch their marshmallow.”

This meant that Jonides and his team had to find a way to measure will power indirectly. Operating on the premise

that the ability to delay eating the marshmallow had depended on a child’s ability to banish thoughts of it, they

decided on a series of tasks that measure the ability of subjects to control the contents of working memory–the

relatively limited amount of information we’re able to consciously consider at any given moment. According to

Jonides, this is how self-control “cashes out” in the real world: as an ability to direct the spotlight of attention so

that our decisions aren’t determined by the wrong thoughts.

Last summer, the scientists chose fifty-five subjects, equally split between high delayers and low delayers, and

sent each one a laptop computer loaded with working-memory experiments. Two of the experiments were of

particular interest. The first is a straightforward exercise known as the “suppression task.” Subjects are given four

random words, two printed in blue and two in red. After reading the words, they’re told to forget the blue words and

remember the red words. Then the scientists provide a stream of “probe words” and ask the subjects whether the

probes are the words they were asked to remember. Though the task doesn’t seem to involve delayed gratification,

it tests the same basic mechanism. Interestingly, the scientists found that high delayers were significantly better

at the suppression task: they were less likely to think that a word they’d been asked to forget was something they

should remember.

In the second, known as the Go/No Go task, subjects are flashed a set of faces with various expressions. At first,

they are told to press the space bar whenever they see a smile. This takes little effort, since smiling faces

automatically trigger what’s known as “approach behavior.” After a few minutes, however, subjects are told to

press the space bar when they see frowning faces. They are now being forced to act against an impulse. Results

show that high delayers are more successful at not pressing the button in response to a smiling face.

When I first started talking to the scientists about these tasks last summer, they were clearly worried that they

wouldn’t find any behavioral differences between high and low delayers. It wasn’t until early January that they had

enough data to begin their analysis (not surprisingly, it took much longer to get the laptops back from the low

delayers), but it soon became obvious that there were provocative differences between the two groups. A graph of

the data shows that as the delay time of the four-year-olds decreases, the number of mistakes made by the adults

sharply rises.

The big remaining question for the scientists is whether these behavioral differences are detectable in an fMRI

machine. Although the scanning has just begun–Jonides and his team are still working out the kinks–the

scientists sound confident. “These tasks have been studied so many times that we pretty much know where to

look and what we’re going to find,” Jonides says. He rattles off a short list of relevant brain regions, which his lab

has already identified as being responsible for working-memory exercises. For the most part, the regions are in the

frontal cortex–the overhang of brain behind the eyes–and include the dorsolateral prefrontal cortex, the anterior

prefrontal cortex, the anterior cingulate, and the right and left inferior frontal gyri. While these cortical folds have

long been associated with self-control, they’re also essential for working memory and directed attention. According

to the scientists, that’s not an accident. “These are powerful instincts telling us to reach for the marshmallow or

press the space bar,” Jonides says. “The only way to defeat them is to avoid them, and that means paying

attention to something else. We call that will power, but it’s got nothing to do with the will.”

The behavioral and genetic aspects of the project are overseen by Yuichi Shoda, a professor of psychology at the

University of Washington, who was one of Mischel’s graduate students. He’s been following these “marshmallow

subjects” for more than thirty years: he knows everything about them from their academic records and their social

graces to their ability to deal with frustration and stress. The prognosis for the genetic research remains uncertain.

Although many studies have searched for the underpinnings of personality since the completion of the Human

Genome Project, in 2003, many of the relevant genes remain in question. “We’re incredibly complicated creatures,”

Shoda says. “Even the simplest aspects of personality are driven by dozens and dozens of different genes.” The

scientists have decided to focus on genes in the dopamine pathways, since those neurotransmitters are believed

to regulate both motivation and attention. However, even if minor coding differences influence delay ability–and

that’s a likely possibility–Shoda doesn’t expect to discover these differences: the sample size is simply too small.

In recent years, researchers have begun making house visits to many of the original subjects, including Carolyn

Weisz, as they try to better understand the familial contexts that shape self-control. “They turned my kitchen into a

lab,” Carolyn told me. “They set up a little tent where they tested my oldest daughter on the delay task with some

cookies. I remember thinking, I really hope she can wait.”

While Mischel closely follows the steady accumulation of data from the laptops and the brain scans, he’s most

excited by what comes next. “I’m not interested in looking at the brain just so we can use a fancy machine,” he

says. “The real question is what can we do with this fMRI data that we couldn’t do before?” Mischel is applying for

an N.I.H. grant to investigate various mental illnesses, like obsessive-compulsive disorder and attention-deficit

disorder, in terms of the ability to control and direct attention. Mischel and his team hope to identify crucial neural

circuits that cut across a wide variety of ailments. If there is such a circuit, then the same cognitive tricks that

increase delay time in a four-year-old might help adults deal with their symptoms. Mischel is particularly excited by

the example of the substantial subset of people who failed the marshmallow task as four-year-olds but ended up

becoming high-delaying adults. “This is the group I’m most interested in,” he says. “They have substantially

improved their lives.”

Mischel is also preparing a large-scale study involving hundreds of schoolchildren in Philadelphia, Seattle, and

New York City to see if self-control skills can be taught. Although he previously showed that children did much

better on the marshmallow task after being taught a few simple “mental transformations,” such as pretending the

marshmallow was a cloud, it remains unclear if these new skills persist over the long term. In other words, do the

tricks work only during the experiment or do the children learn to apply them at home, when deciding between

homework and television?

Angela Lee Duckworth, an assistant professor of psychology at the University of Pennsylvania, is leading the

program. She first grew interested in the subject after working as a high-school math teacher. “For the most part, it

was an incredibly frustrating experience,” she says. “I gradually became convinced that trying to teach a teen-ager

algebra when they don’t have self-control is a pretty futile exercise.” And so, at the age of thirty-two, Duckworth

decided to become a psychologist. One of her main research projects looked at the relationship between self-

control and grade-point average. She found that the ability to delay gratification–eighth graders were given a

choice between a dollar right away or two dollars the following week–was a far better predictor of academic

performance than I.Q. She said that her study shows that “intelligence is really important, but it’s still not as

important as self-control.”

Last year, Duckworth and Mischel were approached by David Levin, the co-founder of KIPP, an organization of

sixty-six public charter schools across the country. KIPP schools are known for their long workday–students are in

class from 7:25 A.M. to 5 P.M.–and for dramatic improvement of inner-city students’ test scores. (More than eighty

per cent of eighth graders at the KIPP academy in the South Bronx scored at or above grade level in reading and

math, which was nearly twice the New York City average.) “The core feature of the KIPP approach is that character

matters for success,” Levin says. “Educators like to talk about character skills when kids are in kindergarten–we

send young kids home with a report card about ‘working well with others’ or ‘not talking out of turn.’ But then, just

when these skills start to matter, we stop trying to improve them. We just throw up our hands and complain.”

Self-control is one of the fundamental “character strengths” emphasized by KIPP–the KIPP academy in

Philadelphia, for instance, gives its students a shirt emblazoned with the slogan “Don’t Eat the Marshmallow.”

Levin, however, remained unsure about how well the program was working–“We know how to teach math skills, but

it’s harder to measure character strengths,” he says–so he contacted Duckworth and Mischel, promising them

unfettered access to KIPP students. Levin also helped bring together additional schools willing to take part in the

experiment, including Riverdale Country School, a private school in the Bronx; the Evergreen School for gifted

children, in Shoreline, Washington; and the Mastery Charter Schools, in Philadelphia.

For the past few months, the researchers have been conducting pilot studies in the classroom as they try to figure

out the most effective way to introduce complex psychological concepts to young children. Because the study will

focus on students between the ages of four and eight, the classroom lessons will rely heavily on peer modelling,

such as showing kindergartners a video of a child successfully distracting herself during the marshmallow task.

The scientists have some encouraging preliminary results–after just a few sessions, students show significant

improvements in the ability to deal with hot emotional states–but they are cautious about predicting the outcome

of the long-term study. “When you do these large-scale educational studies, there are ninety-nine uninteresting

reasons the study could fail,” Duckworth says. “Maybe a teacher doesn’t show the video, or maybe there’s a field

trip on the day of the testing. This is what keeps me up at night.”

Mischel’s main worry is that, even if his lesson plan proves to be effective, it might still be overwhelmed by

variables the scientists can’t control, such as the home environment. He knows that it’s not enough just to teach

kids mental tricks–the real challenge is turning those tricks into habits, and that requires years of diligent practice.

“This is where your parents are important,” Mischel says. “Have they established rituals that force you to delay on a

daily basis? Do they encourage you to wait? And do they make waiting worthwhile?” According to Mischel, even the

most mundane routines of childhood–such as not snacking before dinner, or saving up your allowance, or holding

out until Christmas morning–are really sly exercises in cognitive training: we’re teaching ourselves how to think so

that we can outsmart our desires. But Mischel isn’t satisfied with such an informal approach. “We should give

marshmallows to every kindergartner,” he says. “We should say, ‘You see this marshmallow? You don’t have to eat

it. You can wait. Here’s how.’ ”

The secret of self-control.

Illustration

Caption: Children who are able to pass the marshmallow test enjoy greater success as adults. – BARRY BLITT

DETAILS

Subject: Experimental psychology; Personality traits; Child psychology; Self control; Nuclear

magnetic resonance–NMR; College professors; Children; Psychology; Functional

magnetic resonance imaging (FMRI)

People: Mischel, Walter

Company / organization: Name: Columbia University; NAICS: 611310; Name: Stanford University; NAICS:

611310

Publication title: The New Yorker; New York

Volume: 85

Issue: 14

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Publication year: 2009

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Publisher: Condé Nast Publications, Inc.

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Publication subject: Literary And Political Reviews

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Contributions of Neuroscience to
Our Understanding of Cognitive

Development

Adele Diamond1 and Dima Amso2

1
Department of Psychiatry, University of British Columbia, and Department of Child and Adolescent Psychiatry,

BC Children’s Hospital, Vancouver, Canada; and
2
Sackler Institute for Developmental Psychobiology,

Weill Medical College of Cornell University

ABSTRACT—One major contribution of neuroscience to

understanding cognitive development has been in demon-

strating that biology is not destiny—that is, demonstrating

the remarkable role of experience in shaping the mind,

brain, and body. Only rarely has neuroscience provided

wholly new insights into cognitive development, but often

it has provided evidence of mechanisms by which obser-

vations of developmental psychologists could be explained.

Behavioral findings have often remained controversial

until an underlying biological mechanism for them was

offered. Neuroscience has demonstrated promise for de-

tecting cognitive problems before they are behaviorally

observable—and, hence, promise for early intervention. In

this article, we discuss examples drawn from imitation and

mirror neurons, phenylketonuria (PKU) and prefrontal

dopamine, maternal touch and stress reactivity, and non-

genetic (behavioral) intergenerational transmission of bi-

ological characteristics.

KEYWORDS—plasticity; epigenesis; mothering; executive

functions; animal models; molecular genetics; memory

Neuroscience research has made its greatest contributions to the

study of cognitive development by illuminating mechanisms

(providing a ‘‘how’’) that underlie behavioral observations made

earlier by psychologists. It has also made important contribu-

tions to our understanding of cognitive development by dem-

onstrating that the brain is far more plastic at all ages than

previously thought—and thus that the speed and extent by which

experience and behavior can shape the brain is greater than al-

most anyone imagined. In other words, rather than showing that

biology is destiny, neuroscience research has been at the fore-

front of demonstrating the powerful role of experience throughout

life. Besides the surprising evidence of the remarkable extent

of experience-induced plasticity, rarely has neuroscience given

us previously unknown insights into cognitive development, but

neuroscience does offer promise of being able to detect some

problems before they are behaviorally observable.

PROVIDING MECHANISMS THAT CAN ACCOUNT FOR

BEHAVIORAL RESULTS REPORTED BY

PSYCHOLOGISTS

Here we describe two examples of behavioral findings by psy-

chologists that were largely ignored or extremely controversial

until underlying biological mechanisms capable of accounting

for them were provided by neuroscience research. One such

example concerns cognitive deficits documented in children

treated early and continuously for phenylketonuria (PKU). The

second example involves neonatal imitation observed by psy-

chologists and mirror neurons discovered by neuroscientists.

Prefrontal Dopamine System and PKU Cognitive Deficits

Since at least the mid-1980s, psychologists were reporting

cognitive deficits in children with PKU that resembled those

associated with frontal cortex dysfunction (e.g., Pennington,

VanDoornick, McCabe, & McCabe, 1985). Those reports did not

impact medical care, however. Doctors were skeptical. No one

could imagine a mechanism capable of producing what psy-

chologists claimed to be observing.

PKU is a disorder in the gene that codes for phenylalanine

hydroxylase, an enzyme essential for the conversion of phenyl-

alanine (Phe) to tyrosine (Tyr). In those with PKU, that enzyme is

Address correspondence to Adele Diamond, Canada Research Chair
Professor of Developmental Cognitive Neuroscience, Department of
Psychiatry, University of British Columbia, 2255 Wesbrook Mall,
Vancouver, British Columbia, V6T 2A1, Canada; e-mail: adele.
diamond@ubc.ca.

C U R R E N T D I R E C T I O N S I N P S Y C H O L O G I C A L S C I E N C E

136 Volume 17—Number 2Copyright r 2008 Association for Psychological Science

absent or inactive. Without treatment, Phe levels skyrocket,

resulting in gross brain damage and mental retardation. Phe is an

amino acid and a component of all dietary protein. PKU treat-

ment consists primarily of reducing dietary intake of protein to

keep Phe levels down, but that has to be balanced against the

need for protein. For years, children with PKU were considered

adequately treated if their blood Phe levels were below 600

micromoles per liter (mmol/L; normal levels in the general public
being 60–120 mmol/L). Such children did not have mental re-
tardation and showed no gross brain damage, although no one

disputed that their blood Phe levels were somewhat elevated and

their blood Tyr levels were somewhat reduced (Tyr levels were

not grossly reduced because even though the hydroxylation of

Phe into Tyr was largely inoperative, Tyr is also available in

protein). Since Phe and Tyr compete to cross into the brain, a

modest increase in the ratio of Phe to Tyr in the bloodstream

results in a modest decrease in how much Tyr can reach the

brain. Note that this is a global effect—the entire brain receives

somewhat too little Tyr. How was it possible to make sense of

psychologists’ claims that the resulting cognitive deficits were

not global but limited to the cognitive functions dependent on

prefrontal cortex?

Neuroscience provided a mechanism by which psychologists’

findings made sense. Research in neuropharmacology had shown

that the dopamine system in prefrontal cortex has unusual prop-

erties not shared by the dopamine systems in other brain regions

such as the striatum. The dopamine neurons that project to pre-

frontal cortex have higher rates of firing and dopamine turnover.

This makes prefrontal cortex sensitive to modest reductions in Tyr

(the precursor of dopamine) that are too small to affect the rest of

the brain (Tam, Elsworth, Bradberry, & Roth, 1990). Those un-

usual properties of the prefrontal dopamine system provide a

mechanism by which children treated for PKU could show se-

lective deficits limited to prefrontal cortex. The moderate im-

balance in the bloodstream between Phe and Tyr causes a

reduction in the amount of Tyr reaching the brain that is large

enough to impair the functioning of the prefrontal dopamine

system but not large enough to affect the rest of the brain. Dia-

mond and colleagues provided evidence for this mechanism in

animal models of PKU and longitudinal study of children (Dia-

mond, 2001). That work, presenting a mechanistic explanation

and providing convincing evidence to support it, resulted in a

change in the medical guidelines for the treatment of PKU (blood

Phe levels should be kept between 120 and 360 mmol/L) that has
improved children’s lives (e.g., Stemerdink et al., 2000). Also, by

shedding light on the role of dopamine in the prefrontal cortex

early in development, such work offers insights on the develop-

ment of cognitive control (executive function) abilities that are

relevant to all children.

Mirror Neurons and Neonate Imitation

In 1977, Meltzoff and Moore created a sensation by reporting

that human infants just 12 to 21 days old imitated facial ex-

pressions they observed adults making (see Fig. 1). That was

followed by a second demonstration of such imitation in infants

as young as 42 minutes (Meltzoff & Moore, 1983). For years,

those reports met strong resistance. Such imitation was thought

to be far too sophisticated an accomplishment for a neonate.

After all, infants can feel but not see their own mouth and tongue

movements, and they can see but not feel the mouth and tongue

movements of others. To equate their own motor movements with

the perception of those same movements by others would seem to

involve high-level cross-modal matching.

The discovery of mirror neurons by Rizzolatti and his colleagues,

Fadiga, Fogassi, and Gallese (for review, see Rizzolatti &

Craighero, 2004) provided a mechanism that could conceivably

underlie newborns’ ability to show such imitation rather auto-

matically. Mirror neurons fire when an individual executes an

action or when an individual observes someone else executing that

action. The cross-modal association occurs at the neuronal, single-

cell level. It has since been demonstrated that 3-day-old rhesus

monkeys also imitate the facial movements of adult humans

(Ferrari et al., 2006; see Fig. 1) and that the close link between

perception and action is not limited to vision; hearing a sound

associated with an action activates mirror neurons associated with

that action just as does the sight of that action (Kohler et al., 2002).

Whereas the preceding examples are of neuroscience eluci-

dating possible neurobiological bases for observed psychological

phenomena, we move on to describe phenomena—concerning

plasticity and environmental influences—that neuroscientists

have brought to the attention of developmentalists.

POWERFUL EFFECTS OF EARLY EXPERIENCE ON

BRAIN, BODY, MIND, BEHAVIOR, AND GENE

EXPRESSION

Ironically, one of the most important findings to emerge from

neurobiology is that biology is not destiny. Neuroscience re-

search has shown that experience plays a far larger role in

shaping the mind, brain, and even gene expression than was ever

imagined. This insight is particularly important in advancing

theory in cognitive development, where debates have raged

about the importance of nature versus nurture.

Examples of striking experience-induced plasticity abound—for

example, the groundbreaking work of Greenough, Merzenich, Ma-

urer, Neville, Pascual-Leone, Taub, Sur, and Kral. Here we highlight

work by Schanberg and Meaney, in part because that work em-

phasizes a sensory system that has received far less attention by

psychologists than have vision and audition: the sense of touch.

Nurturing Touch and its Importance for Growth

Two independent, elegant lines of work have demonstrated the

powerful effects of touch. Schanberg and colleagues have shown

that the licking behavior of rat mothers is essential for the growth

of rat pups. If rat pups are deprived of this touch for even just

Volume 17—Number 2 137

Adele Diamond and Dima Amso

1 hour, DNA synthesis is reduced, growth-hormone secretion is

inhibited, and bodily organs lose their capacity to respond to

exogenously administered growth hormone (Butler, Suskind, &

Schanberg, 1978; Kuhn, Butler, & Schanberg, 1978). Schanberg

and colleagues have identified molecular mechanisms through

which deprivation of the very specific kind of touch rat mothers

administer to their pups produces these effects (e.g., Schanberg,

Ingledue, Lee, Hannun, & Bartolome, 2003).

Nurturing Touch and its Importance for Reducing Stress

Reactivity and for

Cognitive Development

Meaney and colleagues have demonstrated that rat moms who

more frequently lick and groom their pups produce offspring

who, throughout their lives, explore more, are less fearful, show

milder reactions to stress, perform better cognitively as adults,

and preserve their cognitive skills better into old age (Liu,

Diorio, Day, Francis, & Meaney, 2000). It is the mother’s be-

havior that produces these effects rather than a particular ge-

netic profile that produces both a particular mothering style and

particular offspring characteristics. Pups of high-licking-and-

grooming moms raised by low-licking-and-grooming moms do

not show these characteristics, and pups of low-touch moms

raised by high-touch moms do show this constellation of attri-

butes (Francis, Diorio, Liu, & Meaney, 1999).

Furthermore, rats tend to raise their offspring the way they

themselves were raised, so these effects are transmitted inter-

generationally, not through the genome but through behavior.

Fig. 1. Imitation of a human adult’s tongue protrusion by a neonatal human and a neonatal rhesus
macaque. Top pictures are reprinted from ‘‘Imitation of Facial and Manual Gestures by Human
Neonates,’’ by A.N. Meltzoff and M.K. Moore, 1977, Science, 198, p. 75. Copyright 1977, American
Association for the Advancement of Science. Reproduced with permission. Bottom photos are from
the study reported in Ferrari et al. (2006). They are reproduced here with the permission of Annika
Paukner and Steve Suomi.

138 Volume 17—Number 2

Cognitive Development

Biological offspring of low-touch moms who are cross-fostered to

high-touch moms lick and groom their offspring a lot; in this way

the diminished stress response and cognitive enhancement is

passed down through the generations (Francis et al., 1999).

Meaney and colleagues have elegantly demonstrated that

maternal behavior produces these behavioral consequences

through several mechanisms that alter gene expression. Not all

genes in an individual are expressed—many are never ex-

pressed. Experience can affect which genes are turned on and

off, in which cells, and when. For example, methylation (at-

taching a methyl group to a gene’s promoter) stably silences a

gene; demethylation reverses that process, typically leading to

the gene being expressed. High licking by rat mothers causes

demethylation (i.e., activation) of the glucocorticoid receptor

gene, hence lowering circulating glucocorticoid (stress hor-

mone) levels as receptors for the stress hormone remove it from

circulation.

Nurturing Touch and Human Cognitive and Emotional

Development

Unlike newborn rats, human newborns can see, hear, and smell,

as well as feel touch. Yet despite the additional sensory infor-

mation available to them, touch is still crucial. Human infants

who receive little touching grow more slowly, release less growth

hormone, and are less responsive to growth hormone that is ex-

ogenously administered (Frasier & Rallison, 1972). Throughout

life, they show larger reactions to stress, are more prone to de-

pression, and are vulnerable to deficits in cognitive functions

commonly seen in depression or during stress (Lupien, King,

Meaney, McEwen, 2000).

Touch plays a powerful role for human infants in promoting

optimal development and in counteracting stressors. Massaging

babies lowers their cortisol levels and helps them gain weight

(Field et al., 2004). The improved weight gain from neonatal

massage has been replicated cross-culturally, and cognitive

benefits are evident even a year later. It is not that infants sleep

or eat more; rather, stimulating their body through massage in-

creases vagal (parasympathetic nervous system) activity, which

prompts release of food-absorption hormones. Such improved

vagal tone also indicates better ability to modulate arousal and

to attend to subtle environmental cues important for cognitive

development. Passive bodily contact also has substantial stress-

reducing, calming, and analgesic effects for infants and adults

(e.g., Gray, Watt, & Blass, 2000; see Fig. 2). Thus, besides

‘‘simple touch’’ being able to calm our jitters and lift our spirits,

the right kind of touch regularly enough early in life can improve

cognitive development, brain development, bodily health

throughout life, and gene expression.

FUTURE DIRECTIONS

Neuroscience may be able to make extremely important con-

tributions to child development by building on repeated dem-

onstrations that differences in neural activity patterns precede

and predict differences in cognitive performance. Often, when

the brain is not functioning properly, people can compensate so

their performance does not suffer until the neural system be-

comes too dysfunctional or until performance demands become

too great. Thus, an underlying problem may exist but not show up

behaviorally until, for example, the academic demands of more

advanced schooling exceed a child’s ability to compensate.

So far, differences in neural activity patterns have been

demonstrated to precede and predict differences in cognitive

performance only in adults. For example, Bookheimer and col-

leagues tested older adults (ranging in age from 47 to 82 years)

with a genetic predisposition for Alzheimer’s disease, selected

because they performed fully comparably to controls across

diverse cognitive tasks. Nevertheless, functional neuroimaging

revealed that the brains of several of the genetically predisposed

individuals already showed predicted differences. Two years

Fig. 2. Double-bedded premature twins. Born 12 weeks early, these twins
were initially whisked into separate incubators. Kyrie (on the right), the
larger by over 2 pounds, slept peacefully, but Brielle (on the left) had
breathing and heart-rate problems, didn’t gain weight, and fussed when
anyone tried to comfort her. Finally a nurse, acting counter to hospital
regulations, put the two sisters together. As Brielle dozed, Kyrie put her
arm around her smaller sibling. Brielle began to thrive. Sooner than ex-
pected, the girls went home. Today a handful of institutions use double
bedding, which reduces the number of hospital days.

Volume 17—Number 2 139

Adele Diamond and Dima Amso

later, those individuals showed the cognitive impairments pre-

dicted by their earlier neural-activity patterns (Bookheimer

et al., 2000). Similarly, adults in the early stages of other dis-

orders may show no behavioral evidence of a cognitive deficit

while neuroimaging shows their brains are compensating or

working harder to achieve that behavioral equivalence. As the

disease progresses, the compensation is no longer sufficient and

the cognitive deficit becomes evident (e.g., Audoin et al., 2006).

What this suggests is that functional neuroimaging in

developing children may perhaps be able to detect evidence

of learning disorders—such as attentional, sensory-processing,

language, or math deficits—before there is behavioral evidence

of a problem. Already, research is being undertaken to see

if infants’ neural responses to auditory stimuli might be pre-

dictive of later linguistic problems (e.g., Benasich et al., 2006).

The earlier a problem can be detected, the better the hope of

correcting it or of putting environmental compensations in place.

Recommended Reading
Diamond, A. (2001). (See References). Summarizes studies with young

children and animals showing the role of maturation of prefrontal

cortex in the early emergence of executive function abilities and

the importance of dopamine for this.

Grossman, A.W., Churchill, J.D., Bates, K.E., Kleim, J.A., & Green-

ough, W.T. (2002). A brain adaptation view of plasticity: Is synaptic

plasticity an overly limited concept? Progress in Brain Research,
138, 91–108. Argues that synaptic, even neuronal, plasticity is but
a small fraction of the range of brain changes that occur in response

to experience, and that there are multiple forms of brain plasticity

governed by mechanisms that are at least partially independent,

including non-neuronal changes.

Meaney, M.J. (2001). Maternal care, gene expression, and the trans-

mission of individual differences in stress reactivity across gen-

erations. Annual Review of Neuroscience, 24, 1161–1192. Provides
an overview of research demonstrating that naturally occurring

variations in maternal care modify the expression of genes

affecting offspring’s cognitive development as well as their ability

to cope with stress throughout life, and that these changes are

passed down intergenerationally (epigenetic inheritance).

Meltzoff, A.N., & Decety, J. (2003). What imitation tells us about social

cognition: A rapprochement between developmental psychology

and cognitive neuroscience. Philosophical Transactions of the
Royal Society of London – B: Biological Sciences, 358, 491–500.
Reviews the psychological evidence concerning imitation in hu-

man neonates and the neurophysiological evidence of a common

coding at the single cell level (in mirror neurons) between per-

ceived and generated actions.

Neville, H.J., & Bavelier, D. (2002). Human brain plasticity: Evidence

from sensory deprivation and altered language experience. Prog-
ress in Brain Research, 138, 177–188. Summarizes research, using
behavioral measures and neuroimaging, on individuals with al-

tered visual, auditory, and/or language experience, showing ways

in which brain development can, and cannot, be modified by en-

vironmental input, and how that varies by the timing of the altered

input and by specific subfunctions within language or vision.

Acknowledgments—AD gratefully acknowledges grant sup-

port from the National Institute on Drug Abuse (R01 #DA19685)

during the writing of this paper.

REFERENCES

Audoin, B., Au Duong, M.V., Malikova, I., Confort-Gouny, S., Ibarrola,

D., Cozzone, P.J., et al. (2006). Functional magnetic resonance

imaging and cognition at the very early stage of MS. Journal of the
Neurological Sciences, 245, 87–91.

Benasich, A.A., Choudhury, N., Friedman, J.T., Realpe Bonilla, T.,

Chojnowska, C., & Gou, Z. (2006). Infants as a prelinguistic model

for language learning impairments: Predicting from event-related

potentials to behavior. Neuropsychologia, 44, 396–441.

Bookheimer, S.Y., Strojwas, M.H., Cohen, M.S., Saunders, A.M., Peri-

cak-Vance, M.A., Mazziota, J.C., et al. (2000). Patterns of brain

activation in people at risk for Alzheimer’s disease. New England
Journal of Medicine, 343, 450–456.

Butler, S.R., Suskind, M.R., & Schanberg, S.M. (1978). Maternal be-

havior as a regulator of polyamine biosynthesis in brain and heart

of the developing rat pup. Science, 199, 445–447.

Diamond, A. (2001). A model system for studying the role of dopamine

in prefrontal cortex during early development in humans. In C.

Nelson & M. Luciana (eds.), Handbook of developmental cognitive
neuroscience (pp. 433–472). Cambridge, MA: MIT Press.

Field, T., Hernandez-Reif, M., Diego, M., Feijo, L., Vera, Y., & Gil, K.

(2004). Massage therapy by parents improves early growth

and development. Infant Behavior & Development, 27, 435–
442.

Ferrari, P.F., Visalberghi, E., Paukner, A., Fogassi, L., Ruggiero, A., &

Suomi, S. (2006). Neonatal imitation in rhesus macaques. PLoS
Biology, 4, 1501–1508.

Francis, D., Diorio, J., Liu, D., & Meaney, MJ. (1999). Nongenomic

transmission across generations of maternal behavior and stress

responses in the rat. Science, 286, 1155–1158.

Frasier, S.D., & Rallison, M.L. (1972). Growth retardation and emo-

tional deprivation: Relative resistance to treatment with human

growth hormone. Journal of Pediatrics, 80, 603–609.

Gray, L., Watt, L., & Blass, E.M. (2000). Skin-to-skin contact is anal-

gesic in healthy newborns. Pediatrics, 105, 1–6.

Kohler, E., Keysers, C., Umiltà, MA., Fogassi, L., Gallese, V., & Riz-

zolatti, G. (2002). Hearing sounds, understanding actions: Action

representation in mirror neurons. Science, 297, 846–848.

Kuhn, C.M., Butler, S.R., & Schanberg, S.M. (1978). Selective de-

pression of serum growth hormone during maternal deprivation in

rat pups. Science, 201, 1034–1036.

Liu, D., Diorio, J., Day, J.C., Francis, D.D., & Meaney, M.J. (2000).

Maternal care, hippocampal synaptogenesis and cognitive devel-

opment in rats. Nature Neuroscience, 3, 799–806.

Lupien, S.J., King, S., Meaney, M.J., & McEwen, B.S. (2000). Child’s

stress hormone levels correlate with mother’s socioeconomic status

and depressive state. Biological Psychiatry, 48, 976–980.

Meltzoff, A.N., & Moore, M.K. (1977). Imitation of facial and manual

gestures by human neonates. Science, 198, 75–78.

Meltzoff, A.N., & Moore, M.K. (1983). Newborn infants imitate adult

facial gestures. Child Development, 54, 702–709.

140 Volume 17—Number 2

Cognitive Development

Pennington, B.F., VanDoornick, W.J., McCabe, L.L., & McCabe, E.R.B.

(1985). Neuropsychological deficits in early treated phenylketonuric

children. American Journal of Mental Deficiency, 89, 467–474.

Rizzolatti, G., & Craighero, L. (2004). The mirror-neuron system. An-
nual Review of Neuroscience, 27, 169–192.

Schanberg, S.M., Ingledue, V.F., Lee, J.Y., Hannun, Y.A., & Bartolome,

J.V. (2003). PKC mediates maternal touch regulation of growth-

related gene expression in infant rats. Neuropsychopharmacology,
28, 1026–1030.

Stemerdink, B.A., Kalverboer, A.F., van der Meere, J.J., van der Molen,

M.W., Huisman, J., de Jong, L.W., et al. (2000). Behaviour and

school achievement in patients with early and continuously treated

phenylketonuria. Journal of Inherited Metabolic Disorders, 23,
548–562.

Tam, S.Y., Elsworth, J.D., Bradberry, C.W., & Roth, R.H. (1990). Me-

socortical dopamine neurons: High basal firing frequency predicts

tyrosine dependence of dopamine synthesis. Journal of Neural
Transmission, 81, 97–110.

Volume 17—Number 2 141

Adele Diamond and Dima Amso