We've studied human intelligence for centuries and still have few answers to what makes us think how we think and know what we know. Are men smarter than women, or vice versa? Are IQ tests biased? Does a bigger brain correlate to higher intellect?

What we do know about human intelligence has mostly been gleaned through intelligence testing (with IQ tests) that tends to focus on human analytical abilities. What we don't know far outweighs what we do know, but we have theories. Many, many theories. Here, we'll dive into 10 theories of human intelligence that have been disproved (or if not disproved, they've been highly criticized). Remember, a theory is just a guess until it's proven. One of these disproved theories may one day be proved. But for now, let's begin with whether or not heredity plays a role in human intelligence.