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 blindness¹. 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.

One immediately plausible hypothesis: the patient is unable to cope psychologically with the possibility of being paralyzed, so he responds with denial. Plausible, but according to Dr. Ramachandran, wrong. He notes that patients with left-side strokes almost never suffer anosognosia, even though the left side controls the right half of the body in about the same way the right side controls the left half. There must be something special about the right hemisphere.

Another plausible hypothesis: the part of the brain responsible for thinking about the affected area was damaged in the stroke. Therefore, the patient has lost access to the area, so to speak. Dr. Ramachandran doesn't like this idea either. The lack of right-sided anosognosia in left-hemisphere stroke victims argues against it as well. But how can we disconfirm it?

Dr. Ramachandran performed an experiment² where he "paralyzed" an anosognosiac's good right arm. ...

nickdevlin

nickdevlin

nickdevlin

nickdevlin