How can I tell is someone is intellegent?....

I can tell if someone is intellegent by the way they talk and the way they present themself. Normally when a person is smart they talk and make sense and you usually don't know what the are talking about. They use alot of big words and they are dressed very profressional. Some cases that I see most in life are that they often times don't have alot to say but are very intellegent. When I picture a smart person i see someone wearing glasses a breifcase and a mustache that has a accent. Although I know that is just an image. Also I think that when you see a person reading a book all the time they are usually smart.