It’s not exactly like above but children are given a marshmallow and told if they wait a certain amount of time and not eat it, they will get another marshmallow and they can eat both. They can decide to eat the marshmallow right away and not get a second one. As well.

It’s a test that has a very high rate of predicting how well a person does in the future, education, life, income, happiness. Indicating people who wait for a second marshmallow do better in life.

It got famous, and when the study was done properly with actual controls and accounting for income, home life and parental trust decades later the previous results are moot. Results are entirely manipulated by how trustworthy the test giver is. So it’s meaningless now in the use I had for it, but the first study’s meaning has lingered.