The effect on the test behavior of children, as reflected in the I.Q. scores, when reinforced after each correct response.

The researcher gave one group of preschoolers an M&M every time they answered a Stanford-Binet item correctly.

A second group took the same test with no candy.

Both groups were typical kids with no diagnoses.

The candy group scored higher on the IQ test than the no-candy group.

One small edible after each right answer was enough to lift scores.

McGarty et al. (2018) extends the same logic to parents: a 50-cent token paid to caregivers after each home session lifted kids’ print knowledge.

Wolchik et al. (1982) ran a parent lottery—caregivers earned tickets when their child hit language targets—again showing that adult payoff boosts child gains.

Peterson (1968) came earlier and showed that how you spread reinforcement changes what children do, foreshadowing why a single M&M can reorganize test taking.

Together these studies say: if you want to see a child’s best performance, first check what’s reinforcing the responses right now.

IQ scores gate special-ed eligibility and gifted placement. A child who has never been reinforced for right answers may look less capable than they are. Before you label, ask: “What’s the reinforcement history during testing?” Bring edibles or tokens to the next assessment and see if scores shift.