What Did the Marshmallow Test Really Show?

The experiments were run by Walter Mischel at Stanford's nursery school in the late 1960s and early 1970s, and the marshmallow was one of several treats on offer; pretzels and cookies were used too. Mischel's original interest was not in predicting the future but in what children do while they wait. The ones who managed it did not stare the marshmallow down. They covered their eyes, sang, kicked the table, turned away, or pretended the treat was a cloud. The lesson he drew was that self-control is a matter of technique, of redirecting attention, rather than of gritting the teeth.

The famous follow-up came later and almost by accident. In the 1980s Mischel tracked down some of the original children, then teenagers, and found that the seconds they had waited correlated with their parents' ratings of their competence and with their scores on university entrance tests. Later follow-ups found associations with body mass index and other outcomes into adulthood. The sample was small, a few dozen children of Stanford academics, and Mischel himself was cautious about it. The public was not.

In 2018 Tyler Watts, Greg Duncan and Haonan Quan ran the test again with more than nine hundred children from a national sample far more varied in income and background than a university nursery school, and followed them to age fifteen. The correlation between waiting and later achievement was there but was about half the size of the original, and most of it vanished once the researchers controlled for family income, the home environment and the child's early cognitive ability. Among children of the least educated mothers, waiting longer predicted almost nothing.

The reading that emerged is that the marshmallow test was measuring, in large part, the child's circumstances. A child from a stable home where promised treats reliably arrive has good reason to wait. A child who has learned that adults' promises are not kept, or that food may not be there later, is being sensible to eat now. A 2013 study made the point directly: children who had just seen a researcher break a promise waited a quarter as long as children who had seen one kept.

It would be wrong to say the test showed nothing. Self-regulation in childhood does predict later outcomes across many studies, and the ability to delay gratification is part of it. What the replication removed was the idea that a single measure at four fixes a child's fate, and the idea that the trait is a fixed quantity inside the child rather than a skill shaped by what the child has learned to expect. Mischel's own emphasis, on the strategies the waiting children used, has held up well and is the part that can be taught.

The story also became a case study in how a finding travels. The original papers were careful; the summaries were not; the video clips of squirming toddlers were irresistible; and a study of a few dozen privileged children became a policy argument about character education. The 2018 result was widely reported as a debunking, which overstated it in the other direction. The honest summary is a small effect, mostly explained by environment, with a technique inside it worth keeping. What each stage of the research found:

• •1970s: children who distract themselves wait longer; self-control is a strategy
• •1980s and 1990s: in a small sample, waiting time correlates with later achievement
• •2010s: trust in the adult strongly affects how long a child waits
• •2018: in a large diverse sample, the link is half as strong and mostly explained by background

The practical conclusions point away from testing children and towards changing what they can rely on. Keep promises, so that waiting has a track record of paying off. Teach the tricks the successful waiters invented on their own: look away, do something else, think about the treat as a picture rather than a taste. And treat a child who grabs the marshmallow as a child responding to a world, not as a diagnosis. A four-year-old's decision about a sweet is a decision about whether the future can be trusted, and that is something adults can do a great deal about.

The marshmallow test found that young children who could wait for a bigger reward used attention-shifting strategies, and a small follow-up suggested they did better later in life. A large 2018 replication found the link much weaker and mostly explained by family background and trust, so the surviving lesson is that self-control is a learnable technique shaped by whether waiting has ever paid off.