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Friday, October 12, 2001


I read an interesting article in one of my psych journals the other day which did a simple experiment that showed markedly different results for ADHD people than normals. The experiment consisted of a set of letters flashed in sequence, and had two tasks: One of the letters was blue while the others weren't, and the subject had to say what the blue letter was. Also, there was a pre-designated "probe" letter for each trial (e.g., the letter "G" or whatever) and the subject had to say whether it appeared in the sequence after the blue letter.

Normals are worse at noticing the probe when it comes soon after the blue letter, presumably because they're still busy processing the identity of the blue letter. As the probe letter moves further away, this effect diminishes until about 700ms or so at which point the probe is identified with the same accuracy as in the control case where there's no blue letter to confound the task.

ADHD people respond just like normals (quantitatively as well as qualitatively) except that they don't get better as the probe moves further away. In effect, once their attention is caught by the blue letter, they can't switch back to looking for the probe.

The basic hypothesis which this supports is that ADHD people have poor volitional control over focus, but normal automated focus response to stimulus. I.e., ADHD people are drawn to whatever their innate mechanisms decide is "interesting", but they have poor ability to willfully override this and focus on something else instead.

Hence, for instance, the classic trait of wanting to read a chapter of a school text, but being literally unable to do it -- not merely "deciding it's not really important" as many non-ADHD folks might accuse, but literally being unable to focus on the text despite profound and sincere conscious effort to do so. In short, if the text isn't inherently interesting in some way to the ADHD reader, it simply will not capture their focus, and they lack the volitional pathway to override this.

One is reminded of the theorized hunter/farmer dichotomies -- it's certainly easy enough to imagine how these two different styles of focus may each be beneficial in different contexts. I also wonder how it correlates to the Mapper/Packer dichotomy--I suspect ADHD folks are far more likely to be Mappers, and normals to be Packers.

Why? Because our inherent metric of interest is based on what is both novel and yet comprehensible to us -- the frontiers of our knowledge. By contrast, something that's either old hat or so disconnected from our current knowledge base that it's just jibberish is not the sort of thing to capture one's attention. Of course, I've just described school, or certainly at least the first twelve years of it, since no class can possibly be paced to exist always at the frontiers of every student's knowledge -- rather, students are required to exercise their volitional control over their focus in order to attend to stuff that's often inherently not interesting, or perhaps more relevantly to my point, often inherently either beyond or beneath their comprehension.

The normal student has the advantage, then, of being able to pack away knowledge which they don't necessarily understand at the time, which they can then pull out and potentially apply some time in the future. The ADHD student can't do it -- if it doesn't map into their current world model, they simply can't grasp it with their attention, and it slips away.

And this is why ADHD is seen as a disability to be cured with Ritalin or other amphetamines which seem to bolster that volitional control of focus (or perhaps they quell the automated one?).

But wait... do we really want to turn everyone into Packers? It may sound functional on the surface, but clearly there are some contexts in which it is vital to be a Mapper. And more generally, the ability to assimilate what you don't understand directly translates to the ability to assimilate things which aren't true, since by definition the assimilator has no applicable world model to check the information against and fit it to.

So, the inability of ADHD people to volitionally control their focus is also a protection mechanism against assimilating false information.

It's no wonder our society is so hot to cure it.

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Simon Funk / simonfunk@gmail.com