(If you don't feel like reading the following I should tell you now that this is way cooler larger on black.)
This is a fairly decent - though by no means perfect - illustration of how my attention span typically operates.
When I want to do something, learn something, build something, write something, or even just ponder something, the actual amount of time I spend is fairly small relative to what generally is considered "normal" - however during that time my focus is far greater relative to the same, & my productivity is explosive.
Unfortunately, most social institutions in which progress is required are not designed to work with this system of development.
Attention deficit hyperactivity disorder (adhd) really isn't appropriately-named; there isn't any real deficit of attention - in fact we have quite an impressive amount - it's just distributed differently. I liken the difference in distribution (specifically of attention span) to runners: particularly long-distance runners vs sprinters.
Assume for this example each one is adept only at their respective style. Those of us with adhd more closely resemble the sprinters in that our attention doesn't tend to last very long, but during that time our attention is intense, solid, & damn near impenetrable - a state referred to as hyperfocus. However, when we try to run longer distances at a reasonable pace - or moderately focus on one topic for extended periods of time - it can present us with varying degrees of difficulty. As I said: we typically have around the same amount of attention as anyone else, our brains simply distribute it in different ways. And when you think about it, that in itself really isn't a problem - or a disorder - at all. Something is a disorder in the technical sense only when it creates a problem in ones life.
The difficulty here is that the cultures in which most of us live today are optimized for slow & steady long-distance runners (I'm not suggesting you're a slow thinker if you don't have adhd, but moderate & steady just sounded too strange), or people whose brains generally function at moderate paces for extended periods of time (also, I'm not equating moderately-paced brain functions with intelligence here, I'm simply using the image to differentiate those whose brains operate at wildly different paces from those whose brains operate at steady paces).
Think about that for a moment: schools are designed to grow our knowledge gradually over long periods of time; most "standard" jobs/careers require us to make a little bit of progress on everything each day; we're taught that slow & steady always wins the race. But the turtle didn't beat the rabbit because the rabbit was quick & sporadic; he beat the rabbit because the rabbit managed to completely forget about the damn race.
The turtle beat the rabbit because the rabbit was a cocky dumbass.
Had the rabbit only understood he had adhd & actually focused on the race in his own way (without falling asleep in the middle of it - a trait attributed more to cocky dumbassery rather than adhd), all other things equal, they probably would have tied.