Are You Anosognosic?

Eliezer Yudkowsky

Are You Anosognosic? — LessWrong

22 Are You Anosognosic?

by Eliezer Yudkowsky

19th Jul 2009

1 min read

22

Followup to: The Strangest Thing An AI Could Tell You

Brain damage patients with anosognosia are incapable of considering, noticing, admitting, or realizing even after being argued with, that their left arm, left leg, or left side of the body, is paralyzed. Again I'll quote Yvain's summary:

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".

A brief search didn't turn up a base-rate frequency in the population for left-arm paralysis with anosognosia, but let's say the base rate is 1 in 10,000,000 individuals (so around 670 individuals worldwide).

Supposing this to be the prior, what is your estimated probability that your left arm is currently paralyzed?

Added: This interests me because it seems to be a special case of the same general issue discussed in The Modesty Argument and Robin's reply Sleepy Fools - when pathological minds roughly similar to yours update based on fabricated evidence to conclude they are not pathological, under what circumstances can you update on different-seeming evidence to conclude that you are not pathological?

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Eliezer Yudkowsky17y100

I strongly suspect that a Less Wrong reader with anosognosia would at first reply, "Well, of course I'm not certain that my left arm isn't paralyzed - you can't be infinitely certain about anything." And they might well go on to say, "But the fact that I don't feel any absolute certainty along these lines is, in fact, evidence that I don't have anosognosia".

I have seen many would-be rationalists who say "I'm not certain" and then, secure in having proven their rationality as much as anyone could possibly ask, forge straight on without a second glance. See The Proper Use of Humility.

eirenicon17y10

I'm still having trouble with this one. I don't know why this particularly morbid example popped into my head, but here it is: we have very strong survival instincts. These can be overcome by overdosing on pills or jumping off a bridge. However, they cannot be overcome by holding your head in a bucket of water and trying to drown. You may be determined to kill yourself, but every time you try, as soon as you start breathing water you're going to pull your head back out. Now, I can say that "I'm not certain" I can't kill myself this way -- but in ... (read more)

0eirenicon17y

That was precisely my first reaction, and in fact I originally wrote that admitting you can't be certain your left arm isn't paralyzed may seem like a stronger defense against an accusation of anosognosia than claiming infinite certainty. However, I realized that saying you can't be absolutely certain your left arm is not paralyzed while absolutely denying that it is seems like a pretty obvious contradiction. The very reason we're talking about anosognosia is because it is unique in that you aren't saying "I'm not certain, but I don't think I'm paralyzed," but "I'm not certain, but I completely reject any evidence that I'm paralyzed." I don't fully understand the condition, though. Would a Less Wrong reader with anosognosia be able to realize he had it if you confronted him on the notion, not that he is paralyzed, but that he is totally rejecting the evidence instead of exhibiting real uncertainty? Difficult to wrap my head around. I did study logic for a while, though, and it gave me an unfortunate predilection for resolving to certainty when I should at least be providing reasonable probability bounds.

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