The experiment was "simplicity itself," its creator, psychologist Walter Mischel, would later recall. The principal ingredient was a cookie or a pretzel stick or — most intriguingly to the popular imagination — a marshmallow.
In what became known as "the marshmallow test," a child was placed in a room with a treat and presented with a choice. She could eat the treat right away. Or, she could wait unaccompanied in the room, for up to 20 minutes, and then receive two treats in reward for her forbearance.
Conducting their work at a nursery school on the campus of Stanford University in the 1960s, Dr. Mischel and his colleagues observed responses that were as enlightening as they are enduringly adorable. Some children distracted themselves by putting their fingers in their ears or nose. At least one child caressed the marshmallow as he hungered for it. Only about 30 percent of the children managed to wait for the double reward.
Mischel, who continued his career at Columbia University and died Sept. 12 at 88, followed a cohort of the children for decades and presented his findings to mainstream readers in his 2014 book "The Marshmallow Test: Why Self-Control is the Engine of Success."
His daughter Linda Mischel Eisner of New York City confirmed the death and said her father died at his home of pancreatic cancer.
His observations, widely noted and hotly debated, were striking: Children who had found ways to delay gratification, he found, had greater success in school, made more money and were less prone to obesity and drug addiction.
"What emerged from those studies is a different view of self-control, one that sees it as a matter of skill" and not a matter of "gritting your teeth," said Yuichi Shoda, a professor of psychology at the University of Washington who worked with Mischel as a graduate student.
As worried parents conducted marshmallow tests at home, policymakers, educators and motivational speakers found a compelling catchphrase: "Don't eat the marshmallow!" Even the ravenous Cookie Monster, a mainstay of the children's TV show "Sesame Street," was coaxed to resist a cookie.
Meanwhile, some psychologists challenged Mischel's findings, arguing that a study group drawn from the privileged environs of Stanford could hardly yield reliable results. Skeptics noted that while affluent families might teach their children to delay gratification, in an effort to encourage financial and other forms of responsibility, children from disadvantaged homes learn that waiting to eat might mean not eating at all.
Mischel defended his research, emphasizing that in no way did he wish to suggest a laboratory performance — particularly by a preschooler — was destiny. The question, he said, is "how can you regulate yourself and control yourself in ways that make your life better?"
Walter Mischel was born Feb. 22, 1930, to a Jewish family in Vienna. His home was not far from that of Sigmund Freud, the founder of psychoanalysis. "Even as a young child I was aware of his presence," Mischel once told the British Psychological Society, "and I suspect at some level I became quite interested in what makes people tick."
Mischel's family enjoyed a comfortable life until the rise of Nazism. His father, a businessman who had suffered from polio, was made to limp through the streets without his cane. Mischel recalled being humiliated by members of the Hitler Youth who tread on his new shoes. The experience, he told the Guardian, planted in him a desire to understand "the enabling conditions that allow people to go from being victims to being victors."
After the Nazi annexation of Austria in 1938, the family fled the country and settled eventually in New York City, where they ran a five-and-dime store. Mischel, who became a U.S. citizen in the 1950s, helped support the family by working in an umbrella factory and as an elevator operator.
He was a 1951 psychology graduate of New York University and received a master's degree from the City College of New York in 1953 and a PhD from Ohio State University in 1956, both in clinical psychology. He taught at Harvard University before settling at Stanford.
He said he became fascinated by the development of self-control in children by watching his daughters emerge from infancy into girlhood.
"I began with a truly burning question," he told the Guardian. "I wanted to know how my three young daughters developed, in a remarkably short period of time, from being howling, screaming, often impossible kids to people who were actually able to sit and do something that required them to concentrate. I wanted to understand this miraculous transformation."
The subjects of the Stanford nursery-school tests were his daughters' classmates. As the children grew up and he noticed correlations between their childhood self-control and future success, he decided to pursue the question more rigorously, through longitudinal study.
He conceded the limitations of his study group at Stanford. "It was an unbelievably elitist subset of the human race, which was one of the concerns that motivated me to study children in the South Bronx — kids in high-stress, poverty conditions," he told the Atlantic in 2014, "and yet we saw many of the same phenomena as the marshmallow studies were revealing."
Mischel proposed strategies for delaying gratification, such as putting the object at physical distance, by removing it from view, or at symbolic distance by imagining it to be something else. A marshmallow is not a sugary treat, for example, but rather a cotton ball.
In his own life, he reported success at resisting chocolate mousse by imagining the dessert to be covered in roaches. A self-described "three-packs-a-day smoker, supplemented by a pipe ... supplemented by a cigar," he said he conquered his addiction by recalling the image of a lung-cancer patient he had seen at Stanford, branded with X's where he would be treated by radiation.
In addition to "The Marshmallow Test," Mischel wrote and co-authored numerous texts on personality, child development and other fields of psychological research. He retired last year after more than three decades at Columbia.
In addition to Eisner, survivors include his partner of nearly two decades, Michele Myers of New York; daughters Judy Mischel of Chicago and Rebecca Mischel of Portland, Oregon; and six grandchildren.
Mischel professed to have found hope in his life's work. "If we have the skills to allow us to make discriminations about when we do or don't do something," he told The New Yorker magazine, "we are no longer victims of our desires."
"It's not," he said, "just about marshmallows."