“As an undergraduate student in psychology, I was taught that multiple personalities were a very rare and bizarre disorder. That is all that I was taught on ... It soon became apparent that what I had been taught was simply not true. Not only was I meeting people with multiplicity; these individuals entering my life were normal human beings with much to offer. They were simply people who had endured more than their share of pain in this life and were struggling to make sense of it.”
― Deborah Bray Haddock, The Dissociative Identity Disorder Sourcebook
Core: Also known as the original or the original child, the core is considered by some to be the part first born to the body. Some see the core as the owner of the system, the part that has the most power and influence over other parts, and the most important part whom the other parts were created to protect. Others see the core as nothing more than the self state that began to integrate sooner than other self states did. There is currently a debate over the existence of cores because it does not easily fit with the theory of structural dissociation. Not all systems have a part that could be identified as a core.
Host: The host is the alter who most commonly uses the body. Host alters collectively fall under the category of fronters, or alters who frequently “front” by taking control of the body and the front, conscious part of the mind. Host alters are responsible for most aspects of daily life, though teams of fronter alters might divide up daily life into more manageable and specialized units such as socialization, academia, work, and taking care of the body. If the host has spent years unaware of the existence of other alters and the trauma that created them, the host might have an extremely hard time coming to accept their DID. This alter might be used to viewing themselves as the only entity in their body and will likely at least at first view themselves as the core. This may or may not be correct. According to the theory of structural dissociation, all hosts are apparently normal parts.
Protector: Protectors are alters who protect the body, system, host, core, or other specific alters or groups of alters. Physical protectors might take or try to prevent physical abuse or become aggressive in an attempt to defend against physical abuse. Verbal protectors might take verbal abuse or lash back verbally in order to counter verbal abuse. Emotional protectors might take emotional abuse or comfort other alters to soften the effects of emotional abuse. Sexual protectors might take sexual abuse or attempt to instigate sexual abuse in an attempt to feel more in control of the situation. Caretakers are one type of protector and are focused specifically on looking after younger, weaker, or more vulnerable alters. Persecutors are another specific type of protector that are often not seen as such but that work to protect by harming the system themselves in order to avoid outside harm.
Persecutor: Persecutors are alters who purposefully harm the body, system, host, core, or other alters, sabotage the system’s goals or healing, or work to assist the system’s abuser(s). Persecutors might hold self hatred or provide an outlet for internalized abusive and negative messages. They may believe that hurting the system or other alters is the only way to control them or teach them how to behave and so prevent further and more extreme abuse from outside abusers. They may be reenacting abuse or trying to ensure that future abuse isn’t more harmful due to being preceded by a period of relatively little abuse. Some persecutor alters are introjects of abusers and may or may not understand that they are not actually the abuser themselves.
Introject: Introjects are alters who are based off of an outside person or figure. Introjects can be based off a family member or adult caretaker who supported the dissociative child and provided a positive influence on their life, serving as a source of potential positive messages for the child to internalize. Introjects can also be based off of historical or fictional figures that the dissociative child found strong, courageous, heroic, or otherwise worthy of being emulated and internalized. Unfortunately, introjects can also be of abusers. Abusive introjects, unlike more positive introjects, provide no comfort or moral compass for the system. Instead, they reenact trauma and abuse, sometimes reinforcing abusers’ lessons to prevent further abuse but sometimes serving as a permanent component of an internal flashback. Introjects may or may not see themselves as the individual that they represent. Introjects that are based off of media or fantasy characters are clinically and academically acknowledged and have been mentioned in sources such as "The Haunted Self" by Onno van der Hart, Ellert R. S. Nijenhuis, and Kathy Steele.
Memory Holder: Memory holders are alters who hold memories that are usually traumatic in nature so that other alters do not have to be confronted by the memories. Other times, memory holders might hold memories of childhood innocence or of being loved by the system’s otherwise abusive or neglectful family. In these latter cases, the memory holder might serve to preserve these memories untainted by memories of trauma or to avoid confronting the system with the pain of what the abuse has cost them. Memory holders are highly associated with abuse takers, alters who experience trauma so that other alters do not have to.
Gatekeeper: A gatekeeper is an alter who controls switching or access to front, access to inside or certain areas inside, or access to certain alters or memories. The existence of a gatekeeper is highly stabilizing for a system because gatekeepers can to some extent prevent unwanted switching, failure to switch when necessary, or failure to switch to the correct alter. They can help to prevent traumatic memories from bleeding from the alters who hold them to alters who could not yet handle them. They might police the boundaries between subsystems. Because gatekeepers have control over which alters have access to front, they themselves are often or always near front and so witness everything that happens to the system. They might experience vast amounts of abuse and might present as ageless, emotionless, and nonhuman as a way to process this and cope. Gatekeepers may or may not also serve as an internal self helper.
Internal Self Helper: An internal self helper is an alter who holds vast amounts of knowledge about the system, alters, trauma, and/or internal workings. For those who believe in cores, internal self helpers are often viewed as the first alter to be created or as the normally pseudo-separate internal voice of logic and reason that all people possess. For those who subscribe to the theory of structural dissociation, internal self helpers are often viewed as observing parts or hidden observers, both less than distinct states. Internal self helpers may or may not also serve as a gatekeeper.
Fragment: A fragment is an alter that is not fully differentiated or developed. Fragments may exist to carry out a single function or job, to hold a single memory or emotion, or to represent a single idea. Depending on the way that individual systems use the term, a fragment might be any alter that could not survive if left on its own or that could not pass for a fully developed individual without the help of other alters. Fragments usually have not been exposed to enough complex, different, or interactive experiences to incorporate more into their sense of self and so become more developed and differentiated. It is possible for fragments to develop into more elaborate alters if the need arises or with further use.
It is important to remember that different systems have different needs, and systems may or may not have one or more alter for each of the above jobs. In smaller systems particularly, alters might hold multiple roles, some of which may even at first seem contradictory. For example, an alter might be persecutory to the system yet strive to protect it from outsiders. Other alters might hold roles that are specific to the system and would be difficult to define or generalize. Alters may hold unexpected roles, such as a child part handling finances or presenting in a persecutory manner. While fragments may be defined by their roles, other parts may be able to act in more complex and less reactive ways. The most well developed alters may be able to handle a wide variety of roles if this becomes necessary for the system's continued functioning. Finally, it should be remembered that an alter's roles can change over time.
-Hart, O., Nijenhuis, E. R. S., & Steele, K. (2006). The haunted self: Structural dissociation and the treatment of chronic traumatization. New York: W.W. Norton.