It may be that certain careers attract people who have specific characteristics and screen out those who do not, but the career itself is not the cause. Playing in the NBA does not make one tall. Pilots are usually task-driven, focused, and detail-oriented. To those who are not, the pejorative "OCD theory" sounds attractive and comfortable. We all tend to think that we're in the center of the behavioral "bell curve", and that it's the other guy who is abnormal.