Your faith, weight, and sexual activity all come into play.

Let's face it: some of us are smarter than others. But is it because of nature or nurture?

Many scientific studies have been conducted to determine the cause of high IQs, and a lot of it boils down to genetics. According to researchers, psychologists and scientists, personal beliefs and physical appearance can also indicate intelligence.

We pulled research from Fox News, CBS, Psychology Today, The Times and more to bring you 20 scientifically-proven signs you're smart. Keep in mind, correlation does not always equal causation!