Aristotle, Nicomachean Ethics
H. Rackham, Ed.

[4] The same thing occurs in other cases when a man tries to do two things at once; the pleasanter activity drives out the other, the more so if it is much more pleasant, until the other activity ceases altogether. Hence, when we enjoy something very much, we can hardly do anything else; and when we find a thing only mildly agreeable, we turn to some other occupation; for instance, people who eat sweets at the theater do so especially when the acting is bad.