Greentext

That's a good point about his concern for consequences.

I definitely think forrest has trouble reading people and social situations, which ties into his candor, or perceived "idiocy".

Gump can usually understand and describe his own thought processes and surrounding environment clearly, even consequences, future events and what people want, like during the war when he can understand the fairly complex notion that his company will quietly last in ambush since the VC are going to come back on their search patrol if they can't find Charlie company, but what he has difficulty perceiving, and more importantly little care or use for, is when people around him have ulterior motives.

When he shows up at Jenny's anti-war rally, he didn't understand what they want or the consequences because nobody, not even Jenny, tells him why they want him to wear chains around his uniform at their rally, he questions her motives and she says

"I axed why again, but she say, "Just do it, you will find out later. You want to make me happy, doesn't you?""

And he accepts that answer.

Forrest understands abstract concepts. He understands personal humiliation, like in the wrestling ring, but has no interest in and so understanding of, figuring out the purposeful deceit or manipulation by others.

It's important to note that while Forrest is the "idiot", everyone around him speaks the same way he does, is surprised by consequences they don't foresee, are very similar to gump himself in the way their lives unfold, with the exception that they don't say what they mean.

In fact, the "smartest" people in the book are the nasa scientists, who immediately realize that gump is much better at math and healthier than most people, and exclaim "your mind is jus like a computer—only better. If we can program it with the right stuff, you will be extremely useful".

Since the scientists are judging gump's raw abilities rather than his interest in social savvy, they can see how intelligent he is, but of course want to use him for their own ends, like everyone else.