The famous psychologist sigmund freud proposed that much of one's adult personality stems from a fundamental conflict between a person's and the necessity to function as a responsible member of society.

The desire to gratify one's physical needs are at conflict in Freudian thought. These drives of food and sex are two of the most well-known. These needs have to be met, he posits, and they sometimes come into conflict with prosocial behaviors that would lead to a properly-functioning human. When these conflicts occur, behaviors that are negative toward others result.