I think I found it (from another forum):
Originally Posted by Washoe
I don’t know if this helps at all, but there’s something I should have mentioned. Although I’ve noticed a very strong correlation between leg jiggling and substance abuse of all sorts, by far the strongest correlation I’ve noted is between leg jiggling and the use of nicotine. Is there any correlation between ADD and nicotine use?
Oh, yes. For many ADDers, it's the drug of choice. It's a stimulant with exquisite control over delivery. It occupies the hands and the mouth. There is a ritual of lighting and behavior involved with it. Boy, oh, boy, yeah. I can't remember the numbers of the top of my head, but it was something like twice the number of unmedicated ADDers smoked than the general population.
I never smoked either. Caffeine is my stimulant of choice, and I don't even get to abuse it that much anymore, since it gives me heart palpitations.
Frylock, the flip side of distractability for those with ADD is the ability to hyper-focus when under pressure. When I was a kid, I would avoid work until the very last possible moment, but by golly, when that moment came, I was sharp as a laser. You could have had a marching band parade through my room, and I'd never have noticed it. If it's not that, then I usually have a radio playing or I put myself not to far from people who aren't studying, because the background noise actually did make it easier for me to study.
There's a symptoms checklist here, if you'd like to investigate it further. And, BTW, though I originally thought the idea was ridiculous and the last thing I needed was another label, understanding ADD and getting appropriate treatment has drastically improved my life. http://boards.straightdope.com/sdmb/sho ... p?t=432616
Nicotine, substance abuse, procrastination, leg shaking, concentrated focus when needed seem to fit. I never thought of ADD since I always did well in school.