Socrates answered this question years ago

You are intelligent if

  • You are infinitely curious. You can learn from any body to every body.
  • You are most humble person out there. You consider the fact that every one has experiences to share and you have an opportunity to learn.
  • Your self awareness is sky high. You understand futility of every thing.You recognize the fact that noting is permanent and no bliss is perfect.

via What are some signs of intelligence?