Human Nature: Fiction writers mistakenly think everyone has “parts.” Psychiatrists and psychologists mistakenly think multiple personality is rare.

“Parts” is an informal term for alternate personalities, which are parts of a person’s mind that seem to be independent, to have minds of their own.

Different parts or personalities have their own memory banks. Although some personalities have joint accounts, are co-conscious, and know pretty much what each other is thinking and doing, other personalities may not even be aware that another personality exists. And often there is one-way awareness: A is aware of B, but B is not aware of A. So B will have a memory gap for any period of time that A had come out and been in control.

Most people feel everyone is basically like they are. And since 90% of fiction writers have multiple personality trait (multiple personality without its causing distress or dysfunction), they may think that everyone is like that.

But since it is probable that less than 30% of the general public has multiple personality trait—and since undiagnosed alternate personalities like to remain incognito—then most people, including psychiatrists and psychologists, will think multiple personality is rare. And it is relatively rare, only about 1% of the general public, if you think of multiple personality only in terms of the mental illness, multiple personality disorder.