What does it really take mentally to be a physicist? No stereotypes, just your objective observations. I believe that a greater than average dissociation from people, although not to the degree of mathematicians, is one important psychological trait of physicists. The ability to project one's internal visualization and experiences onto the external environment helps to apply the ideas of physicists to reality. Dogged, but rational, determination with an equation, concept, phenomenon or theory separates physicists from most other professions. How have the physicists that you have known behaved interpersonally? They must have some such stamina to lecture before large audiences, but even so, many seem introverted outside of their field.