Anyone who has seen a teenager in the grip of an obsession knows that they can work harder than most people. Like a garage tinkerer who will spend hours refining an invention that will save him a few seconds a few dozen times in his life, a teenager can devote enormous persistence to a task that strikes his fancy. If the reward is visible. If the reward is not visible, they are easily distracted into one that is, even if it is a lesser reward.
I have no idea how you're going to use this information, BTW. I certainly haven't figured it out.
Why then, are they so lazy, so unconcerned, about tasks which need to be accomplished - even they know need to be accomplished eventually - but hold no charm?
Because our "achieve reward" and our "avoid discomfort" circuits are separate, and theirs haven't lined up yet. For adults, the connection between the two concepts has developed over time, so we can at least roughly estimate some balance between them. But for teenagers, these two items are still quite separate. Their "achieve reward" circuits are actually more active than an adult's. So active, in fact, that it kicks in for whatever crosses its path. Their energy goes to "the next visible reward." All others, take a number. Rather like the dog-man in the movie who turns his head and says "Squirrel!" Shiny, shiny.
Complicating this is the underdeveloped circuitry for avoiding discomfort. Because teenagers dawdle over anything unpleasant, you would think it would be the opposite - that they do little but avoiding discomfort. Yet it is the underdevelopment, the lack of ability to see that 10x discomfort will occur if you don't endure x comfort now that keeps them unmoved by consequences. 10x, x, it's all the same. My parents are mildly upset, my parents are very upset, it's all the same. I might be embarrassed for a few moments, I might lose my job - those are about equivalent to a teenager.
This is of course entirely understandable to adults, even as it is infuriating. We feel those same impulses on their separate circuits and get the point that one might not want to do something unpleasant. Why not put it off a few more minutes, hours, days? But adults have the better-developed pain avoidance, and can better foresee how painful this is going to be if it is postponed too long.