Identical twins share a home environment and have the same genetic makeup, while fraternal twins share a home environment but do not share the exact same genetic makeup. In studies comparing behavioral traits in identical and fraternal twins, researchers found that genetic differences can account for 40 to 50 percent of differences in personality traits, while environmental influences account for about 30 percent of differences in personality traits. The Role of the Family One surprising finding from behavior genetics concerns the relative lack of influence of family environments on personality development. Except for extremes like severe neglect or abuse, parental behavior has little impact on a child's developing personality. Environmental influences outside the family environment, such as school and friends, are often more important to the development of personality.
People seek out or even create environments to which they are genetically predisposed.
For example, a combative person is more likely than a peace-loving person to find an environment in which arguments are likely to take place, or to create such an environment by starting fights. Genes do not directly influence personality traits. Instead, genes direct the development of the nervous and endocrine systems, the body chemistry that rules our behavior. Looking at personality traits, we should therefore expect to find links to differences in body chemistry and in fact, recent research is discovering these links. All rights reserved.