I am Dx'd as ADHD. My 14 year old son is dx'd as ADHD.
I want to offer an alternative explanation to Thom's Hunter theory. I see the ADH mindset as one that is about rapid adaptation. Some books will look at the condition of ADHD as partially a temporal dysfunction. The ADHD individual is always in "the moment." There is little mental effort put into concerns about future consequences. At a minimum, due to a lack of ability to focus on certain tasks, the thoughts of future consequences are thought of and forgotten in very quick bursts.
I have taught two different children how to play chess. The process of learning is encapsulated well within the game of chess. It involves a broad array of skills and abilities. It involves big ideas of strategy, and smaller ideas of individual tactics. To practice the game you need to learn small skills. But you can't just win with the small skills. You have to include both the big ideas and the small ideas in the game.
My son learned chess in a way that is typical of the ADHD mind. He didn't sit down and focus for long periods of time. In a nutshell, he learned a lot of individual tactics, played a lot of fast games of chess, and eventually through that process he was able to rise to an acceptable level of success at the game for his own tastes. This was a very rapid process where he went from being 40th in the state tournament (not all that awesome), to being 4th in state in the span of a year. It wasn't an anomaly, because he placed in the same position the following year.
The key here, however, is that he basically took the tools that were immediately at hand and adadpted them rapidly to suit his needs. He does things in unconventional ways when he plays chess.
My daughter, on the other hand, learns it in a much different way. She takes a longer time to master the ideas of the tactics. Instead, she is more prone to learning the game by studying, memorizing, and taking time to think through her work. She has had to be told to speed up the thought process by playing quicker games.
So part of my idea here is that more rapid adaptation may be beneficial in some cases, because it specifically removes the distant future as a threat to the current solution. ADHD minds are frequently the types who will kludge things together out of nearby materials, and the specter of planning is often distasteful. I'm sure that this frame of mind exists in other people, but one of the things I notice about the ADHD individual is that he or she may be more inclined to wait until closer to the moment of action. I think this has to do with the fact that the ADHD mind needs to deal with the situation as it currently is, as opposed to the situation as we would like it to be, or as it was at the outset of "planning."
My son and I have very similar behavior patterns. This could be related to nature or nurture. Most likely, as all things tend to be, it is somewhere in between those with a smidge of each.
I thought I'd put that out there for consideration. I think Thom's idea is reasonable, but I wonder if it wouldn't be more beneficial to an indivdual if an individual has a rapidly adapting brain that requires constant distraction in order to accurately assess the current situation. I wonder what we would discover about those who truly exhibit the hallmarks of ADHD if we were to test adaptability to unknown situations.
I think this would help to explain how students with ADHD are somehow able to survive at a sustainable level in academic situations.
Additionally, the idea of the rapid adapting brain would explain the apparently paradoxical affect of stimulates on the ADHD individual. I don't entirely agree with THom's advocacy against stimulant medication. It is extremly beneficial for me. It doesn't appear to be more physically addictive than something like coffee. I can take days off the medication and the most I feel is a certain excitability and less organized thoughts if I don't take it. One time, I heard Thom refer to someone on stimulant meds as a "speed freak." Well, Thom would not recognize my behavior on meds as being that of a speed freak.
One of the reasons I came to this idea is that I was trying to understand what my brain was doing with the stimulants. It's very clear that it is a stimulant on the rest of my body, but my brain seems to immediately do battle with the medication. It occurred to me that it is the attempt of the brain to adapt to the stimulant. It really feels as if my brain is trying its hardest to shut down the overstimulation by suppressing it neurally. It's an interesting paradox, because I have long had the problem of not being able to sleep to do the distractability of the environment. This was the case long before I ever took medication. So the strange part is that I take an amphetamine, and I can lay down and my brain seems like it's ready to sleep, but my body won't let me. Our brain gives us offsetting cues in other cases, so this is not an unfounded notion. If you think about things like the aftermotion effect that is associated with waterfalls (waterfall effect), you'll see my point. The specific neural functions that lead to this are not necessary to understand. Basically, your brain gives you an opposite motion sensation in what appears to be an attempt to bring the newly encountered moving environment into a managable and steady state. Your brain offsets the downward motion so that stationary items appear to be moving upwards.
I have to learn things from scripts from time to time. Rather than memorize a script like many of my coworkers have done, I am best when I learn the material, and essentially recreate the same content as the script by taking the teaching material as the set of tools, and adapting it to the situation. In that way, this is like the example with chess.
Another way to think about it is to consider that question of a change in one's environment. Is an individual more likely to be the active party in changing the environment to suit her needs, or is an individual more likely to be the one adapting oneself to suit the current state of affairs? I would suggest that the ADHD individual may be more inclined towards adapting to suit the environment.
Experiments might include testing the rate of adaption to things like motion, and then comparing those averages to dx'd ADHD patients who exhibit particularly high levels of ADHD behaviors. Perhaps a mild stimulant comparison between previously unmedicated, but dx'd ADHD patients and undx'd ADHD patients.
Just thought I'd put that out there for ADHD people to chew on.