Some people who commented on that post objected to my sociological analysis by referring to evidence that the brains of people diagnosed with ADHD are in some ways different from those of other people. To them, the evidence of a brain difference is somehow proof that ADHD is a "medical" or "biological" disorder and that a sociological analysis of it is out of place. But if you give it some thought, you will quickly realize that there is no contradiction at all between biological and sociological analyses of ADHD or any other condition referred to as a disorder. My goal in that essay was to explain the extraordinary increase in rate of ADHD diagnosis that has occurred over the last two or three decades. I don't think that increase is primarily due to a change in brain structures in the general population; I think it is primarily due to a change in social values and especially in the conditions of schooling. Today, as a society, we are far less tolerant of children who don't adapt well to our system of compulsory education than we were in the past, and so we diagnose them and give them drugs.

For a somewhat (but not fully) analogous case, consider homosexuality. Homosexuality is biologically a condition of the brain; but the decision to label it as a disorder, or not a disorder, is a social judgment. Until 1973, homosexuality was on the American Psychiatric Association's list of official mental disorders, but in that year it was removed. Suddenly, gay people were no longer "disordered." That decision clearly reflected a change in social values, a change that made it possible for people with the brain condition of homosexuality to live happier lives than they had been able to before, when they more or less had to stay in the closet and were subject to terrible abuse and even arrest if they did not. With regard to homosexuality we have as a society become more liberal and accepting. With regard to the kind of childhood rambunctiousness and impulsiveness that leads to a diagnosis of ADHD, however, we have as a society become less liberal and accepting.

The story for ADHD, of course, is not fully analogous to that for homosexuality. The condition we call ADHD is clearly one that can vary in degree. A few people--and I think that is very few people--who are diagnosed with ADHD have the condition to such an extreme degree that most of us would consider it to be a disorder, worthy of some kind of treatment, under almost any social conditions. But most people with the diagnosis have the condition to a much lesser degree than that--a degree that interferes especially with schooling and certain other school-like activities, as they are structured today, but may actually be helpful in other settings.

In the remainder of this essay I'll describe briefly current thinking concerning the cognitive and neural foundations for ADHD and explain further why I think our focus should be on changing our system of schooling to accommodate children's diversity rather than on changing children's brain physiology to accommodate schooling.

The basic cognitive characteristic of ADHD appears to be high impulsiveness and reduced "executive control."

According to the most widely accepted cognitive model of it, the fundamental problem in ADHD is not one of attention so much as one of impulsiveness.[1] By a wide variety of measures, people diagnosed with ADHD are more impulsive, less reflective and controlled, than other people. This impulsiveness is believed to underlie all or most of the distinguishing behavioral characteristics shown by such people. Impulsiveness leads them to be easily distractible, which is why they are seen as inattentive. It also leads them to be impatient and restless, unable to tolerate tedium or to sit still unless something truly grabs and retains their interest, which is why they may be seen as hyperactive. And it leads them to be highly emotionally reactive; they tend to respond immediately, emotionally, overtly, to stressful or otherwise arousing situations. The model is no doubt overly simplistic, but it is nevertheless useful as a beginning point for thinking and talking about ADHD.

Cognitive psychologists and neuroscientists commonly use the term executive control to label the mechanisms by which the brain inhibits impulsive behavior, reflects, and then acts on the basis of reflection rather than impulse. Although executive control is generally thought of as a good thing, it seems obvious that it can also, if too strong, be a bad thing. The opposite of impulsive is inhibited. Some people are too inhibited for their own good. They stew constantly over what is the right thing to do, or over the possible negative consequences of every alternative, and therefore they don't do anything. While the highly controlled person sits and watches an emergency, trying to figure out the best possible response and worrying about the risks, the impulsive person jumps in and saves someone's life.

The value of diversity along the controlled-impulsive personality dimension

Most psychologists would say that psychological wellbeing is maximized by a certain optimal degree of executive control. The overly controlled person suffers from too much inhibition, and the overly impulsive person suffers from too little of it. I agree with that when we are talking about extremes. However, between the extremes there is a broad range on the control-impulsiveness dimension that is potentially quite compatible with psychological wellbeing and contribution to society. The trick, for each person, is to find niches within their environment that play to their strengths rather than to their weaknesses. In general, people who are highly controlled are great in jobs that require lots of reflection and relatively little action, and people who are highly impulsive are great in jobs that require lots of action with relatively little time for reflection. This has nothing to do with degree of intelligence. You can be intelligent and impulsive, making terrific snap judgments; and you can also be intelligent and reflective, making good judgments after thinking things through very carefully.