Even as the rate of diagnosis has reached 11 percent among American children aged 4 to 17, neuroscientists are still trying to understand attention deficit hyperactivity disorder (ADHD). One classic symptom is impulsivity - the tendency to act before thinking.Scientifically, impulsivity can appear as a choice for a small but immediate reward over a larger one that requires some delay. Choosing between present and future rewards is a fundamental need in schooling, says Luis Populin, associate professor of neuroscience at University of Wisconsin-Madison.

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