Researchers at Universitat Autònoma de Barcelona and the Vall d'Hebron University Hospital have now discovered anomalies in the brain's reward system related to the neural circuits of motivation and gratification. In children with ADHD, the degree of motivation when carrying out an activity is related to the immediacy with which the objectives of the activity are met. This would explain why their attention and hyperactivity levels differ depending on the tasks being carried out.
The importance of this to us non-scientists is it's another link between biological processes and behavior. When a kid consistently "misbehaves," the first guess at a cause should be something happening in the brain rather than just a bad kid. That doesn't mean a child care provider could diagnose anything physical from behavior, but providers, parents, and counselors should keep the possibility in mind when figuring out how to deal with what are euphemistically called "challenging behaviors." It won't be many years before the relevant genetic information is available for every kid. We just have to figure out how to use it responsibly. Just.