If you've ever felt like totally giving up on trying to change your character flaws, congratulations! We may have the perfect excuse.

A new study suggests that your personality is determined at birth, and that it may be pretty resistant to environmental factors. Researchers found that subjects generally fell into one of four personality types, based on the volumes of tissues in different parts of their brains.

The four types of personalities are "novelty-seeking" (like your best friend who climbed a tree naked and now has incurable ringworm), "reward-dependence" (that guy who is addicted to everything), "persistence" (stuck-ups and perfectionists) and "harm-avoidance" (grouches, recluses, agoraphobics and other-people-averse types).

The good news? Researchers say that this data can be used to create individualized discipline and learning plans for kids. You know, just like in "Brave New World." (Sorry! We'd be optimistic about it, but we we're physiologically incapable.)