Castration anxiety is the fear of emasculation in both the literal and metaphorical sense. Castration anxiety is an overwhelming fear of damage to, or loss of, the penis—one of Sigmund Freud's earliest psychoanalytic theories. Although Freud regarded castration anxiety as a universal human experience, few empirical studies have been conducted on the topic. Much of the research that has been done on the topic was done decades ago, although still relevant today. The theory is that a child has a fear of damage being done to their genitalia by the parent of the same sex (e.g. a son being afraid of his father) as punishment for sexual feelings toward the parent of the opposite sex (e.g. a son toward his mother). It has been theorized that castration anxiety begins between the ages of 3 and 5, otherwise known as the phallic stage of development according to Freud. Although typically associated with males, castration anxiety is theorized to be experienced in differing ways for both the male and female sexes.