Both genes and environmental factors contribute observed differences in identical twin behavior. Firstly, life experiences can form a huge difference in identical twin behavior. For instance, if one of the twins is bullied, obviously she/he will behave differently than the twin who isn’t bullied. The bullied twin is more likely be depressed or develop violent tendencies. Life experiences are the reason why many identical twins have such a different personality. Even though most identical twins are raised in the same environment and have the same exact genes, one of them is more likely to get a disease due to environmental factors and/or the activation of gene expression. For example, if one of them smokes and drinks she/he is more likely to
