REPLICATING THE MARSHMALLOW EXPERIMENT WITH A LARGER SAMPLE.. I have posted a number of times about the Stanford Marshmallow Experiment. This wikipedia entry explains it. Children were offered a marshmallow with the promise that if they delayed gratification—held off on eating the first marshmallow—they would get a second marshmallow. Years later, it was found that the children who could wait for the second marshmallow were more successful—(for example, on their SAT scores).
The wikipedia entry records that when the experiment was originally done, the number of participants was 16 boys and 16 girls at a nursery school at Stanford. This abstract of the paper also gives a figure of 32 subjects in the test. (The wikipedia entry statement that there were 600 children in the test is a puzzle.) Perhaps because this first test was performed in 1960, little attention seems to have been paid to the small size of the sample.
A recent replication of the test was published in May of 2018 and reported on in this article in the Atlantic by Jessica McCrory Calarco. The researchers used a sample of more than 900 children. This study, says Calarco, suggests that the “capacity to hold out for a second marshmallow is shaped in large part by a child’s social and economic background—and, in turn, that that background, not the ability to delay gratification, is what’s behind kids’ long-term success.”