Taking ADD as high interest-preference, by analogy of time-preference, as the ratio of the present values given to immediate interest (or interestingness, to differentiate it from the economic term, and not to suggest that I have more of a ready definition for this term) vice future interest:
A person of high interest-preference may in class focus on immediately-interesting doodling, whereas a person of low interest-preference may figure on going to Disney World on the income she'll have with the skill she's acquiring in this same class. Which example immediately suggests that the major function of a school is to create an artificially low interest-preference among its students, by force if necessary (a legitimate use: the property owner ejects a distracting element). Similarly a person of low time-preference will make an investment a high-time-preference person would not; and a government may create artificially high time-preference by taxing saving. As societal trends in time-preference influence interest rates, so also may societal trends in interest-preference influence the length and complexity of books and other media.
As people of variable time-preference come together in lending, so may people of variable interest-preference come together in -- what? One example might be that of one student doing the homework of another. The student buying the labor has demonstrated high interest-preference by preferring immediate drunkenness over use of the skills the homework aims to train; the student selling the labor has contrawise demonstrated low interest-preference.
As a firm led by a CEO of lower time-preference may out-compete a firm led by a CEO of higher time-preference, so may people of differing interest-preference may compete -- when?
As people must have time-preference, so may it be said that people must have interest-preference: a person of zero interest-preference would spend a lifetime of drudgery (to what end?) without any anticipated enjoyment. A person of infinite interest-preference would never suffer schooling that was not more intrinsically interesting than any immediate alternative.
... Having said all this, I think I may have just replaced 'time' with 'interest', and 'subjective value' with 'subjective interestingness'. In this case, ADD seems to equate to high time-preference in the case of the single good of leisure.
Well, I don't believe in ADD to begin with. See the Thomas Szasz On Psychiatry thread. But if you mean to imply that ADD is simply laziness or a lack of enthusiasm and interest, I might agree.
I've been playing NWN2 as well lately. I haven't played the expansion that much yet, but I did make it past the hag coven.