But it’s the other guy in my brain who’s guilty

When a personality that’s not me commits a crime, is it a fair punishment to incarcerate the body we share?

And if it’s not, then doesn’t a part of me that I don’t even know get away with it, even get away with murder?

These are the kinds of brain-twisting questions that loom over criminal justice thanks to advances in neuropsychology. And these are the questions that give nightmares to the many who worry about a science-induced end to criminal justice as we know it.

In “Split personality crime: who is guilty?” — a soon to be “paywalled” article published by New Scientist on July 5th — Jessica Hamzelou reports on a study of patients diagnosed with dissociative identity disorder (DID), also known as multiple personality disorder.

The study compared brain scans of high-fantasizing individuals without DID with those of individuals diagnosed with DID. Participants were made aware of a traumatic episode that was imagined by the non-DID subjects, but was known to the “secondary” personality of the DID patients. The idea was to determine if there were differences in the brain activity patterns of the two groups. In other words, if DID were, as its many critics claim, just role playing or imagination, there should be no difference in the ways that the brains of the two groups responded to the prompt.

The results showed a consistent difference in brain activity between the non-DID and DID-diagnosed participants, indicating that DID is something concrete, and not just a form of fantasy.

As indicated by the questions at the start of this posting, the potential impact on the criminal justice system of wider acceptance of the reality of DID is enormous, and enormously complex.

If Fred murders his father, but George doesn’t even know that Fred exists, and indeed doesn’t at all remember the early abuse that triggered Fred’s rage, do you send George to jail? Has George done anything wrong?

I don’t have the space or present inclination to get into these questions here. However, there is another kind of question, more philosophical than legal, that is prompted by this kind of study.

Perhaps the greatest dilemma for psychology is the study of consciousness, in particular the study of the nature and causes of what we call the “self.”

Would validation of DID add weight to the claims of those who argue that the self is a narrative construct, a running story that the mind organizes by providing a protagonist, a conceptual character to whom “happen” all of the experiences that the mind monitors?

If different personalities — different identities — can exist within the same mind, then it can’t be right to persist in claiming that there’s a “person” inside the mind.

The early childhood trauma typically reported by DID sufferers (a word that shows our bias toward the sense that “I” is an actual, single entity) occurs around the age of four. Four is the age at which children make a firm distinction between themselves and others. That is, when they develop a coherent sense of self. Given enough stress, some minds appear to segregate the stress-causing experiences in a separate narrative, in a story kept safely distinct (most of the time, anyway) from the day-to-day narrative lived by the “normal” personality.

It’s intriguing. In some ways, studying DID patients is like studying split brain patients. By exploring the changes caused by the abnormal, we better understand the normal.

Of course, firmly establishing the reality and nature of DID will take a lot more study than the one experiment reported by New Scientist. But when it comes to understanding who, what, and how we are, every step on the way is a good step.

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