Throughout the years, there has been much research on the influence that heredity and genetics play in personality development. As defined by the American Psychological Association website (n.d.), “personality refers to individual differences in characteristic patterns of thinking, feeling and behaving”. These characteristics help to distinguish individuals from each other. These personality traits emerge early and continue throughout the course of their lifespan. Although, personality is unique to the individual, experts in the field of psychology have studied the idea that personality is somewhat based upon biology, therefore implying that the biological makeup plays a role in a person’s personality. Extensive research and indisputable evidence through long-term studies has supported the idea that personality is directly influenced by genetics. Evidence that supports the biological influence on personality development is based on direct evidence through the examination of genes and studies of individuals who have the same genetic makeup. Both identical and fraternal twins are good candidates and are commonly used for genetic studies in medical and psychology research. Throughout history, many twins have been placed in situations where they were raised in completely different environments, therefore they have been utilized in testing to determine the influence of genetics on every aspect of our composition. When discussing personality, most contemporary personality