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. 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  café 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 naïveté 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.’  ” ♦