According to the Lilienfeld text, results from a University of Minnesota study show that genes play a big role in personality. Researchers at the U of M collected a sample of 130 identical and fraternal twins that grew up apart. It was found that identical twins reared apart tend to be very similar in their personality traits. They're also a lot more similar than fraternal twins reared apart. When compared with twins that grew up together, it's shown that identical twins grown up apart are about as similar as identical twins grown up together- suggesting that shared environment plays little or no role in adult personality. Although shared environment plays some role in childhood personality, this role generally subsides as we grow older. This is important to understand, because although there may be some studies showing that shared environment has a big impact- you should check to see whether they were studying children or adults, since as we grow older the connection between environment and personality is generally lost. Something I wonder about is how big of an impact genes have on personality when looking at siblings, not just twins? Would there be any correlation between genes and personality with siblings that grew up separately? Would the environment play a bigger role, since unlike twins, siblings do not share all the same genetic material? Would HOW siblings are being raised have a bigger impact?