In this brief overview, we'll start by identifying some personality traits used in the University of Minnesota 1979-1986 study of more than 350 pairs of twins that have been determined to be traits that are at least 50 percent the result of heredity rather than the result of environment.
- personal intimacy
- social potency
- obedience to authority
- sense of well-being
- vulnerability vs. resistance to stress
- fearfulness vs. risk-seeking
- vulnerability to stress
Some of these traits comprise factors in behavioral personality models, like the Five Factor Model, thus corroboration of the hereditary nature of these traits is high.
Some things that we know for certain about Kennedy are that he battled against enormous odds, such as Addison's Disease and degenerative spinal disease, to become a Navy officer and then President of the United States. This relates to the hereditary factors aggressiveness, social potency and leadership.
Some life experience dominant personality traits that are at least 50 percent determined by environment, gleaned from the same Minnesota study, are:
- inclination to work hard
- goals reaching
- impulsiveness vs. caution
We also know that Kennedy had a sexually immoral side to his life. He had multiple affairs including an affair with a Mafia kingpin's girlfriend. This relates to the environment (life experience) factor of impulsiveness versus caution. It is amplified in intensity by the hereditary factor of fearfulness versus risk-seeking.
In context of Kennedy's home, educational and class environments combined with his father's occupational environment (then head of the Securities and Exchange Commission, SEC), we can analyze this personality expression as coming from the environmentally determined trait of impulsiveness in combination with the hereditary trait of risk-seeking.
This is in accord with Kennedy's upbringing in an environment of wealth, power, prestige. It was an environment that lead to feelings of entitlement to privilege that was explicitly denied to other people since certain privileges, like gaining a commission as a Naval Officer without a medical exam, were either illegal or immoral. It also accords with an obvious hereditary predisposition to high intelligence and aggressiveness.