"Protagoras" is a work of Plato, mostly focusing on a debate between Socrates and the sophist Protagoras about the nature of many things. One of the things they touch on is the nature of intelligence.
Towards the end of the work (349-358, according to the classical page notations), Protagoras mentions that people do evil because they are overcome with pleasure or pain. Letting aside that fact that Protagoras says, (and Socrates does not directly contradict) that pleasure is good and pain is bad, the discussion goes into why some people do things that bring them pain later on, when they should know better.
Socrates does not believe that such a thing could be true, that people could knowingly do something that would injure themselves later on. He says that people who do such things do them because they are not skilled at measuring. That a person who is overcome with pleasure is merely miscalculating the later consequences of their actions, much the same way they may not know that a further sound is louder than a closer, but quieter one.
So Socrates seems to be describing the ability to make intelligent decisions to be based on measurements of possible pain and pleasure derived fromactions. A fairly useful concept of intelligence for most purposes, although I doubt that Socrates would have defined good and evil as being merely well thought out hedonism. He may have just been going under Protagoras' assumptions.
Over all, while it is really not my place to critique Socrates or Plato, the eventual ramifications of this doctrine grew rather far from human life. While defining intelligence (as well as morality) as, in the most literal sense, rationality, a ratio between two possiblities and their outcomes makes sense, eventually this concept metamorphisized into the belief that rationality was not just a way of understanding or reaching the pleasent or the good, but was in itself the highest good. While the ability to form ratios is good, there has something to compare in the beginning, and maybe something better then simple hedonism.
Another thing that follows from this doctrine of ratios that Socrates didn't explicitly state is that once a person is making a metaself that can weigh equally the desires of the moment and of later, that that same metaself can equally well weigh the needs of one person and the other equally. However, I don't know if Greek thought (or even later philosophers who were influenced by the Greeks) were sophisticated enough to realize this.