Marshmallow Test

Mischel's experiments at Stanford's nursery school offered a child one treat now or two for waiting. Follow-ups in 1988 and 1990 linked longer waiting to higher SAT scores in adolescence, and the test became shorthand for self-control as destiny. In 2018 Watts, Duncan and Quan repeated it with a far larger and more varied sample: the association was half the original size, and was cut by two-thirds once family background, early cognitive ability and the home environment were controlled.

In practice

• A school buys a self-control curriculum on the strength of the marshmallow studies, when much of what the test measured was the children's circumstances.
• A parent worries that a four-year-old who ate the biscuit at once is headed for trouble, when the more reliable signal in the test was everything else about the family.

Possible explanations

One explanation is self-control as a stable trait. Another is circumstance: a child who has learned that promised treats do not arrive has good reason not to wait, which experiments using unreliable adults support. A third is that waiting and later achievement both follow from family resources.

In its favour

The original studies were carefully run, and the follow-ups did find an association with later achievement.

Against it

The 2018 replication found that association about half the size, and a third of that again once family background and early ability were controlled, so the test measures circumstances as much as willpower.

Standing

The 2018 replication found a small remaining association, concentrated in whether a child could wait at least twenty seconds at all. The story of willpower as destiny rested largely on the original sample's advantages.

Further reading

Wikipedia

Subject

Learning & Education

Essay

What works in learning, and what schools can and cannot change