I am fascinated by Dissociative Identity Disorder (so much so that I wrote my MA’s dissertation on the subject). DID – also known as multiple personality disorder – is roughly what you might expect it to be, given the numerous fictional portrayals of it. Multiple personalities in one body, sometimes with deeply contradictory desires; sometimes existing simultaneously, sometimes alternating. The stories of Dr. Jekyll and Mr. Hyde and Fight Club’s Narrator and Tyler Durden are, handily enough for explanatory purposes, somewhat accurate portrayals of the condition (Fight Club moreso than Stevenson’s tale).
I’m equally fascinated by how rarely DID seems to be a topic for philosophical and psychological research; to me, it seems to be an important phenomena. There are several reasons, I believe, for this paucity of interest. The first is that questions regarding DID are almost inextricably bound with questions of personal identity, and questions about personal identity are a) somewhat unfashionable, and b) bloody difficult. With regards to a), one merely has to compare the number of papers published on personal identity (three thousand this year, according to Google) to those published on, say, consciousness (nearly twenty thousand) to find evidence for the claim. It is admittedly harder to justify b), but a comment by David Chalmers regarding a paper he wrote on the technological singularity is a good indication of its veracity; “I think this is the first time I've written at any length about personal identity, a topic I've largely avoided in the past as it confuses me too much”. Granted that Chalmers is only a single person, but when one of the pre-eminent contemporary philosophers says that a subject confuses him, then we might take it as good evidence that the subject is a complicated one (to say the least).
Aside from personal identity, DID itself is a controversial subject – which, again, might motivate researchers to avoid it. There have been calls to remove it from the APA’s Diagnostic and Statistical Manual of Mental Disorders; arguments for this proposal cite the condition’s lack of certain causation, tautological diagnostic criteria, possible conflicting interests in the diagnosing physicians, and so on (Gharaibeh, 2009). Evidence for DID includes studies which have demonstrated that patients diagnosed with DID possess smaller hippocampal and amygdalar volumes than average individuals (Vermetten et al., 2006), have disrupted memory processes (Dorahy and Huntjens, 2007) and physiological changes as extreme as one personality state being diabetic whilst the other is not (Braun, 1986). I personally feel that there is sufficient evidence to reasonably assume that something is happening in cases of DID, although more research into the condition's exact effects is needed – something which has not gone unnoticed by psychiatrists; Colin Ross (2006), as an example, laments that “the research literature on dissociative identity disorder is smaller than that on many other Axis I and II disorders.”
One quirk of DID research – which, again, might contribute towards many researcher’s reluctance to study it – is its association with some more outlandish claims. Tales of reincarnation and past lives, energy auras, possession; it is not at all unusual to see those working on DID also pursuing research (of some kind) into such topics. It’s probably not absurd to say that there’s a stigma attached to any investigation into parapsychological topics, and DID’s association with such topics, weak as it is, may well damage its reputation. This is, however, effectively pure speculation on my part.
This discussion leads to the eminently reasonable question; why is DID important? Obviously research into the condition is at least mildly important, for if it exists, then there are sufferers who require aid. This, I think, is inarguable, although we might perhaps argue about what forms of treatment are necessary or desirable. Similarly, there are the questions that it raises for personal identity; what is actually going on in these cases metaphysically, if DID is real? One person with a disrupted sense of self? Multiple persons sharing the same body? An answer is not immediately apparent (nor is it apparent after deliberation – the philosophical literature on DID is divided as to whether or not the disorder features multiple persons).
Yet there is another reason why DID requires more research, one that has been hinted at implicitly by such heavyweights as Edelman, Tononi and Dennett; if it is possible for consciousness to be “split”, and for multiple consciousnesses to exist in one body simultaneously, as seems to be the case in certain patients diagnosed with DID, then any mature theory of consciousness must be able to explain such a phenomena. If DID is not a real phenomena, then there is no need for theories of consciousness to account for it (obviously enough). The three authors above have all at least mentioned dissociative phenomena in their writings (Dennett actually authored a particularly interesting article on multiple personality disorder with Humphrey, which I’ve listed in the references), and all ensure that their theories are compatible with DID’s existence. But is ensuring this compatibility necessary? Erring on the side of caution and assuming DID is a real phenomena is, perhaps, an admirable stance – but if we find enough evidence to conclude that it does not exist, then we may be able to streamline potential theories of consciousness.
A possibility, I think, that should be entertained; hence why more research, both empirical and philosophical, into DID should be considered.
Braun, B.G. (1986), Treatment of multiple personality disorder, New York, APA
Dorahy, M.J., & Huntjens, R. (2007). Memory and attentional processes in dissociative identity disorder: A review of the empirical literature. In E. Vermetten, M.J. Dorahy, & D. Spiegel (Eds.), Traumatic Dissociation: Neurobiology and Treatment (pp. 55-75). Arlington, VA: American Psychiatric Publishing, Inc.
Gharaibeh, N. (2009), Dissociative identity disorder; time to remove it from the DSM?, Current Psychiatry, 8, 9, 30-36
Humphrey N, & Dennett D.C. (1989) Speaking for our selves: an assessment of multiple personality disorder, Raritan, 9, 68–98
Ross, C.A. (2006), Dissociative Identity Disorder, Current Psychosis and Therapeutics Reports, 4 (3), 112-116
Vermetten, E., Schmahl, C., Lindner, S., Loewenstein, R.J. & Bremner, J.D., (2006), Hippocampal and Amygdalar Volumes in Dissociative Identity Disorder, American Journal of Psychiatry, 163, 630-636