Psychologists have long debated whether nature (the effects of genetics) or nurture (the effects of environment) plays a bigger role in the development of a human personality. The major question remains: which has a greater effect on one's personality, nature or nurture?
I don't think anyone's found a definitive answer yet, but the more studies are done, the more we find is because of nature, not nurture. There is no doubtthat BOTH are important.