Watching a four-year-old take the marshmallow test has all the funny-sad cuteness of watching a kitten that can’t find its way out of a shoebox. The child sits with a marshmallow inches from her face. Most lean in to smell it, touch it, pull their hair, and tug on their faces in evident agony over resisting the temptation to eat it. Except, that is, for the blissful ones who pop it into their mouths.
The marshmallow test, invented by Walter Mischel in the 1960s, has just one rule: if you sit alone for several minutes without eating the marshmallow, you can eat two marshmallows when the experimenter returns. Decades later when Mischel and colleagues caught up with the subjects in their original studies, they found something astonishing: the kids who were better at resisting the treat had better school achievement as teenagers. This early research led to hundreds of studies developing more elaborate measures of self-control, grit, and other “noncognitive skills.
The takeaway from this early research was that self-control plays an important role in life outcomes. The message was certainly not that there was something special about marshmallows that foretold later success and failure. And yet, a new study of the marshmallow test has both scientists and journalists drawing the exact wrong conclusions.
Observing a child for seven minutes with candy can tell you something remarkable about how well the child is likely to do in high school.
According to sociologist Jessica McCrory Calarco, writing in The Atlantic, this new study “has cast the whole concept into doubt.” In her view this is one more in a long line of studies suggesting that “psychology is in the midst of a ‘replication crisis.’” The Guardian described the study with the headline, “Famed impulse control ‘marshmallow test’ fails in new research.” A researcher quoted in the story described the test as “debunked.” So how did the marshmallow test explode so spectacularly?
In the new study, researchers gave four-year-olds the marshmallow test. Then they compared their waiting times to academic-achievement test performance in the first grade, and at 15 years of age. The result? Kids who resisted temptation longer on the marshmallow test had higher achievement later in life. The correlation was in the same direction as in Mischel’s early study. It was statistically significant, like the original study. The correlation was somewhat smaller, and this smaller association is probably the more accurate estimate, because the sample size in the new study was larger than the original. Still, this finding says that observing a child for seven minutes with candy can tell you something remarkable about how well the child is likely to do in high school. So where’s the failure?
The researchers next added a series of “control variables” using regression analysis. This statistical technique removes whatever factors the control variables and the marshmallow test have in common. These controls included measures of the child’s socioeconomic status, intelligence, personality, and behavior problems. As more and more factors were controlled for, the association between marshmallow waiting and academic achievement as a teenager became nonsignificant. Calarco concluded that the marshmallow test was not about self-control after all, but instead it reflected affluence. Children from lower-class homes had more difficulty resisting the treats than affluent kids, so it was affluence that really influenced achievement. This was the basis for cries of “replication failure!” and “debunked!”
When the future is uncertain, focusing on present needs is the smart thing to do.
The problem is that scholars have known for decades that affluence and poverty shape the ability to delay gratification. Writing in 1974, Mischel observed that waiting for the larger reward was not only a trait of the individual but also depended on people’s expectancies and experience. If researchers were unreliable in their promise to return with two marshmallows, anyone would soon learn to seize the moment and eat the treat. He illustrated this with an example of lower-class black residents in Trinidad who fared poorly on the test when it was administered by white people, who had a history of breaking their promises. Following this logic, multiple studies over the years have confirmed that people living in poverty or who experience chaotic futures tend to prefer the sure thing now over waiting for a larger reward that might never come. But if this has been known for years, where is the replication crisis?
The great thing about science is that discoveries often lead to new and deeper understandings of how different factors work together to produce outcomes. Mischel’s marshmallow test inspired more-elaborate measures of self-control and deeper theories linking impoverished environments to diminished self-control. Those theories—and piles of data—suggest that poverty makes people focus on the short term because when resources are scarce and the future is uncertain, focusing on present needs is the smart thing to do. However, when chronic poverty leads to a daily focus on the present, it undermines long term goals like education, savings, and investment, making poverty worse.
Poverty doesn’t work in straight lines; it works in cycles. But that means that researchers cannot isolate the effect of one factor simply by adding control variables. That’s why researchers say, “What nature hath joined together, multiple regression analysis cannot put asunder.” While it may be tempting to think that achievement is due to either socioeconomic status or self-control, we have known for some time that it’s more complicated than that. Early research with the marshmallow test helped pave the way for later theories about how poverty undermines self-control. We should resist the urge to confuse progress for failure.