In a stand-up routine, Lewis Black rails that the crawlers on news channels cause ADD. If, below news being read to us, something bombards us with fleeting, unrelated tidbits, of course we have ADD.
Good for chuckles, to be sure, but there’s also a valid point here. I remember reading somewhere that the average American 11 year-old has knows more information than did the average adult back in the Mayflower days (citation needed, I know). By extension, the average American 11 year-old recognizes thousands of musical tunes, whereas the average pilgrim probably knew fewer than 30 (if they were even permitted such an indulgence as music at all). If you think about it, the modern era is a battleground for information selection with copious sums of music, movies, television shows, YouTube videos, internet memes, and endless other media competing for our attention.
With regard to ADD, we cannot assume that hyperstimulating environments cause increased births with insufficient attentional abilities. There simply have not been adequate generations to precipitate any such change in genomics. Clearly, if any variable ought to be examined, it’s nurture on a single generation basis (no need for an excessive evolutionary time course). Human beings presumably have had attentional capacities ranging along a standard normal curve for millenia. In environments containing regular levels of stimuli (relative to a natural environ typical of prehistoric human ancestors), people acclimate favorably to settings requiring focus; there’s no precedent for development as though there are too many stimuli to process. As such, fewer individuals stand out as having difficulty managing focused tasks. Without superfluous stimuli constantly flooding their senses, they develop into functional adults without obvious learning problems.
This creates a model of increased environmental attentional demands ~ increased probability of adaptation by limited attention. Only the truly worthy stimuli get focused on, and everything else can be rapidly flipped through like a paperback novel. In a climate of dense information maelstroms, this is adaptive. In the classroom, of course, it is a hindrance.
So ultimately, ADD may very well be this: some proportion of people have a propensity to adapt to growing stimulatory demands by their brain literally limiting their attentional capacity to accommodate for a more competitive information arena. They must be a) more selective and b) able to jump from stimulus to stimulus rapidly without getting too involved. Quick assessments must be made to maintain the economy of attentional energies when processing vast sums of data. Like stress-related ulcers, ADD disposition didn’t get agitated into a maladaptive state until vast industrialization occurred.
How to test this: ideally, you take identical twins and raise one in a simpler, less media-dominated environment. The other is raised in your average middle class setting with ample access to television, internet, and so on. Compare the onset or exhibition of attentional traits.