I just listened to an interview with Daniel Kahneman, the author of Thinking Fast and Thinking Slow. He made a remark about an interesting case. Suppose that a person is informed that a loved one needs immediate surgery in order to save her life, and that this surgery has a 99% success rate (i.e., only 1% of patients do not survive the surgery). Kahneman suggests that this is one of many cases in which people behave irrationally. Most people, he suggests, would be very nervous and fearful that the person they love would die. He points out that this is irrational because there is but a very small percentage of people that do not survive the surgery. This verdict doesn't seem right to me. To call such people irrational or to say that such emotions aren't apt for the situation strikes me as a mistake. It seems to me that because the stakes or so high (a person's life is on the line) the 1% chance is rather significant. If the situation involved something with lower stakes, then I'd be prepared to say of such a person that she were irrational or not appreciating the statistical facts in forming her beliefs, emotions, etc. Consider a different case: Suppose that I have a cold and my physician says that such-and-such a treatment has a 99% chance of substantially reducing my symptoms and a 1% chance of exacerbating them. In this sort of case, it seems right to say that I would be irrational in believing that my condition would get worse upon taking the medication. It would be strange for me to feel afraid of taking it. It seems to me that the statistics matter and must inform our beliefs, guide our emotions, etc. But it also seems understandable that the stakes/severity of the possible consequences matter and can help explain why a person might think or feel certain things; indeed, such considerations might even justify what would otherwise be a bad inference/ill-formed reaction.
What do you think of all this?
(I should confess that I haven't read his book yet. Maybe he offers
some replies to my worry. It's on my list for summer reading and hope
to get to it soon.)