Sigmund Freud was an influential Austrian psychologist who created psychoanalysis. He proposed that the mind is divided into the id, ego, and super ego. According to Freud, the leader of a crowd is able to suspend rational thought and tap into primal urges, similar to how a hypnotist influences others. As a result, crowd behavior is driven by impulse and emotion rather than reason, and crowds act in antisocial, childlike ways.