Dissociative Identity Disorder (DID) is a severe condition in which two or more distinct identities, or personality states, are present in—and alternately take control of—an individual. Norman and Dan are examples of this. The end of Psycho, when Norman is given a blanket at the Police station was a really good example of how DID takes over the individual.

In addition to a different personality, someone with DID also experiences memory loss that is too extensive to be explained by ordinary forgetfulness. DID was called Multiple Personality Disorder till 1994 when it was changed to DID so people could better understand its fragmentation and splintering of identity rather than by separate identities. For example, a person who had DID has identity fragmentation, meaning they have a mixed self-identity, rather then two separate personalities. Like Norman and Dan, neither of them really believed they were someone else entirely, they were both individuals at the same time.

DID also reflects a failure to integrate various elements of memory, self- consciousness, and self-identity. The primary identity of someone with DID usually consist of the person’s given name. In this state he or she tends to be more passive, guilty, depressed, and dependent, remember how normal Norman and Dan were when they were just themselves. However, when DID is in control, each personality state may be experienced as if it has it’s own history and self-image. In this state, his or her name, reported age and gender, vocabulary, predominant mood, and general state of mind is altered.

Interestingly, the multiple identities that a person with DID experiences can deny knowledge of each other existence, be critical of one another, enjoy one another, or even be in conflict.