If I were a subject in the marshmallow test as a child, I would have eaten it right away! I had unreliable parents and didn’t trust adults to tell the truth. If I had waited to eat it, they have said “What marshmallow? Who said anything about getting a marshmallow?” They would eat the marshallow themselves. The marshmallow test says more about how children perceive the reliability of the adults in their life than anything else.
