As promised, let's talk about Attention Deficit Disorder! I have to note here that, while I am a psychologist, ADD as such is far from my specialty. Nevertheless, I have come to believe that motivation can indeed affect attention, whether it is the "formal" ADD or not. WARNING: Some of this is speculation!
Everyone has all three of the main motives, but to different degrees--often widely varying. As far as the research seems to show, the distribution is mostly random--you could be high or low on them in any combination. However, it is unlikely for you to be high in all three. It's like rolling three dice--it's likely one will be high, less likely that two, and very unlikely that all three will come out high. Most people generally have one high, one in the mid-range, and one low.
There are exceptions, however: some people have more than one above the median. Also, if you have a low motive temporarily aroused, you might find yourself with double (or triple) high motivation. What does this mean?
I asked David McClelland once what kind of person had all three motives high. He said: "Confused."
Why is this so? Think about it. These motives are about emotional engagement--what you find fun, enjoyable, exciting, or what frustrates you to be without. But we are talking about very different things!
Achievement motive: doing things better, improving or making more efficient, taking moderate-but-challenging risks. Affiliation motive: getting along with people in a friendly way, belonging to a group, enjoying people. Influence/Power motive: having an impact or influence on others. Two are about people, the third is not. One is focused on getting along, the other two are not. One is about doing the best regardless of people, the other two aren't. You get the idea.
With more than one motive high, different things will attract you. Some situations pull on all three motives, but in different directions! Say you are on a team working on a project, and one person isn't doing well. The Power motive is whispering: "help the guy--coach him a bit." The Affiliation motive is saying "but it will hurt his feelings to know he's not doing well." And the Achievement motive is saying "Gangway! Competent person taking over!"
Now these are all sources of energy, too. This means that you need a lot of self-control to manage all this. I have observed (and it is a worthy area to study) that some people can "switch gears" readily whereas others seem to have problems focusing with one motive at once. Furthermore, just holding back your impulses takes self-control. Here's the kicker (finally): If you have three motives high and insufficient impulse control, you will be interested in everything and acting impulsively in (at least) three different directions. You won't be able to stick to one thing, because while you are satisfying one motive, the other two are getting "backed up" and frustrated, and eventually the restless energy will push you out of what you are doing and into something else. Sounds like ADD, doesn't it?
But wait, there's more! As I suggested earlier, it is possible for you to get a motive temporarily aroused. Happens all the time--meeting a new friend raises Affiliation, a difficult phone conversation raises Affiliation or Power, a big meeting raises Power, a structured situation with a clear goal and lots of measurement tends to raise the Achievement motive. So you could move from one motive well under control, to two motives, generating more energy than you can handle! The bigger the stress (and you remember last time I said there are motive-specific stressors, don't you?), the bigger the arousal.
I knew a person who was normally low on Affiliation--not excessively, but clearly not above the median--and extraordinarily high on Achievement motive. Normally he was an easygoing but energetic person: whatever worked, he liked, and he would patiently explain things as necessary. Then he went through an ugly divorce (two kids, one step), and at one point was screaming--no joke--at the staff in the office because something had been slightly delayed. His energy, always high, had exceeded his ability to manage it, because his Affiliation motive had been cranked to the ceiling by the conflict, and it wasn't a motive he was even used to dealing with. He became very difficult and impatient for a while.
What I am suggesting here is that, first of all, you can handle some kinds of stresses better than others; and secondly, that you can move from focused to having attention problems if you suddenly have multiple motives firing at once. Third, of course, is that if you are already high in multiple motives, you are going to look as if you have ADD, even if you don't. And I wonder if this is why some treatments don't work--they're treating the wrong thing.
I should note in passing that the way many ADD drugs work is to actually push people over the top of the Yerkes-Dodson "arousal bell curve," so that energy starts paradoxically decreasing. Ritalin is a stimulant! But stimulants only affect certain neurological systems, while each motive has its own related neurochemical system: Achievement has been linked to ADH, Affiliation to dopamine, and Power to epinephrine and norepinephrine. (There are some recent studies showing links with testosterone as well, which I have to read up on!) So it is possible for someone to get a drug which may exacerbate a motive excess.
Even people with a single very high motive--and insufficient impulse control--can have symptoms resembling those of ADD as well. One other symptom, I am told, is "hyperfocus." The idea seems to be that you can overfocus or underfocus, but not just focus appropriately! Well, a motive is emotional engagement, right? If you have just one motive very high, and find a task perfectly suited for it, it may be downright addictive in its attraction! On the other hand, without an appropriate task, you might be unable to channel that excess energy. Multiple motives, as noted, would just make it worse.
So perhaps that restless inability to focus is based on multi-motivational stress, eh?
As I said, this is speculative, but I suspect that I'm onto something here--or at least have found something that may contribute difficulties for people who definitely have ADD!