Sunday, May 22, 2016


The brain is weird:
Rationalists complain that most people are too willing to make excuses for their positions, and too unwilling to abandon those positions for ones that better fit the evidence. And most people really are pretty bad at this. But certain stroke victims called anosognosiacs are much, much worse.

Anosognosia is the condition of not being aware of your own disabilities. To be clear, we're not talking minor disabilities here, the sort that only show up during a comprehensive clinical exam. We're talking paralysis or even blindness. Things that should be pretty hard to miss.

Take the example of the woman discussed in Lishman's Organic Psychiatry. After a right-hemisphere stroke, she lost movement in her left arm but continuously denied it. When the doctor asked her to move her arm, and she observed it not moving, she claimed that it wasn't actually her arm, it was her daughter's. Why was her daughter's arm attached to her shoulder? The patient claimed her daughter had been there in the bed with her all week. Why was her wedding ring on her daughter's hand? The patient said her daughter had borrowed it. Where was the patient's arm? The patient "turned her head and searched in a bemused way over her left shoulder".

Why won't these patients admit they're paralyzed, and what are the implications for neurotypical humans? Dr. Vilayanur Ramachandran, leading neuroscientist and current holder of the world land-speed record for hypothesis generation, has a theory. . . .

So what's Dr. Ramachandran's solution? He posits two different reasoning modules located in the two different hemispheres. The left brain tries to fit the data to the theory to preserve a coherent internal narrative and prevent a person from jumping back and forth between conclusions upon each new data point. It is primarily an apologist, there to explain why any experience is exactly what its own theory would have predicted. The right brain is the seat of the second virtue. When it's had enough of the left-brain's confabulating, it initiates a Kuhnian paradigm shift to a completely new narrative. Ramachandran describes it as "a left-wing revolutionary".

Normally these two systems work in balance. But if a stroke takes the revolutionary offline, the brain loses its ability to change its mind about anything significant. If your left arm was working before your stroke, the little voice that ought to tell you it might be time to reject the "left arm works fine" theory goes silent. The only one left is the poor apologist, who must tirelessly invent stranger and stranger excuses for why all the facts really fit the "left arm works fine" theory perfectly well.
That the brain has one module for defending our existing beliefs, and a second one for occasionally modifying those beliefs in the light of new evidence, is immediately compelling to me. To me the two processes feel very different: expounding my existing beliefs is something I can do by rote without really engaging my reasoning apparatus to any great degree. But in the face of a significant attack, my mind has to go into another gear and really start thinking about what is the truth here. I could swear I have felt this shift from routine discourse to real analysis take place.

And of course all the people I have told this to say "That explains Republicans!" or whatever group it is they are tired of arguing with.

But wait, there's more:
It gets weirder. For some reason, squirting cold water into the left ear canal wakes up the revolutionary. Maybe the intense sensory input from an unexpected source makes the right hemisphere unusually aroused. Maybe distorting the balance sense causes the eyes to move rapidly, activating a latent system for inter-hemisphere co-ordination usually restricted to REM sleep. In any case, a patient who has been denying paralysis for weeks or months will, upon having cold water placed in the ear, admit to paralysis, admit to having been paralyzed the past few weeks or months, and express bewilderment at having ever denied such an obvious fact. And then the effect wears off, and the patient not only denies the paralysis but denies ever having admitted to it.
A bizarre result that, of course, inspires fantasies of squirting water into our enemies' ears:
My mouth is still agape at that whole cold-water-in-the-ear trick. I have this fantasy of gathering all the leading creationists together and squirting ice cold water in each of their left ears. All of a sudden, one and all, they admit their mistakes, and express bafflement at ever having believed such nonsense. And then ten minutes later the effect wears off, and they're all back to talking about irreducible complexity or whatever. I don't mind. I've already run off to upload the video to YouTube.

No comments: