Well, stop it.

Fidgeting, as it turns out, helps kids with Attention-Deficit Hyperactivity Disorder focus. So just like grown-ups need a cup of coffee before tackling a problem, kids with ADHD may tap their feet, swivel in their chairs or bounce in their seats while their brains are busily figuring out that math test.

That's the conclusion of a groundbreaking study conducted by a team at the University of Central Florida. The team, led by Dr. Mark Rapport, studied 23 pre-teen boys — 12 with ADHD and 11 without — and watched how the boys tackled problems that taxed their "working memory," the short-term memory that most of us use unconsciously each day.

The tests were not easy: The boys were shown a series of numbers, then a few seconds later, asked to recall the numbers and rearrange them in order. In another test, they were shown a visual pattern and then asked to recall it, using the computer keyboard.

As they worked on the problems, the boys with ADHD spun around in their swivel chairs. They tapped their hands and feet and jiggled around. Even the movements that were not obvious on videotape were picked up by actigraphs, an activity monitor that the boys wore like watches.

"Everybody moves more when they're concentrating on the tasks, not just the ADHD kids," said Rapport, a former school psychologist who now studies the disorder at the Children's Learning Clinic at UCF. "But the ADHD kids moved significantly more," and as the tasks got harder, the kids jiggled and bounced and spun more. Why? Rapport said that, just as adults drink coffee to stay alert during a boring meeting, ADHD kids jiggle and wiggle to maintain alertness.

Parents naturally wondered why the kids, who bounce around during school hours, can sit still and play a video game or watch a movie.

But Rapport found that when he showed the preteen boys an exciting scene from "Star Wars," all of them sat very still — because they did not have to concentrate to watch the movie. Likewise, even with video games, kids were not using working memory — the higher-level thinking required of much schoolwork.

What makes ADHD kids different? Rapport suspects they are "under-aroused" — that their brains do not produce enough dopamine to keep them alert during normal day-to-day activities — so the kids move around to jiggle or wake their brains and bodies up.

For many teachers, like Darcey Eckers of Orlando, Rapport's findings confirmed what she has seen in years of teaching.

"These kids have to move," Eckers said. "It can be any kind of movement — some part of their body, it doesn't even matter what part."

But at some schools, such movement is frowned upon. Eckers, who teaches second grade at Rosemont Elementary in Orange County, takes a different tack. If the children are more comfortable standing or pacing while they work, they can move to the back of the classroom.