Personality seems so intangible – and is expressed through so few behaviours and habits – that it is hard to believe that it is carried within our genes. Studies have consistently shown that personality is heritable, because 50% of variation in personality can be attributed to our genes.
If 50% of personality is heritable, 50% still comes from the environment. However, parenting and the household environment have found to have little impact on your personality. Researchers have not yet pointed the factors that account for the other 50%.
Also, personality can be explained by its connection with our brain. The famous case of ill-fated railroad worker Phineas Gage, whose personality changed dramatically after an injury to the front of his brain, was an early indicator that personality and brain are linked. Nowadays, scientists know that the pre-frontal cortex is responsible for planning and impulse control. Some scientists believe that people who are scored high on Neuroticism scale in personality tests easily activate their limbic system. Limbic system is brain structures that are associated with emotion. Levels of neurotransmitters – chemicals that ferry information across brain cells – also seem to vary according to personality. Studies showed that the enzyme mono-amine oxidase (MAO), which breaks down neurotransmitters, is lower than average in people with sensation-seeking personalities. It might be that these wild partiers and fast driver have neurotransmitter levels that are simply too high for safety.