The most intelligent and able forecasters are incapable of making predictions
Yes. precisely because they suffer from the biases mentioned. Sure predicting the future is really tough. But it isn't helped by the presence of severe biases. It is important to realize that intelligent doesn't mean one is less likely to be subject to cognitive biases. Nor, does being an expert in a specific area render one immune- look at the classic conjunction fallacy study with the USSR invading Poland. It is true that even taking that into account predicting the future is really hard. But if one looks for signs of the obvious biases then most predictions problems show up immediately.
Your argument about updating my probability upwards because I don't understand the future is fascinating. Can you explain why I can't use the precise same argument to say there is a 50% chance that Arizona will be destroyed by a super-bomb on January 1st 2018?
Well, you should move your uncertainty in the direction of 50% probably. But there's no reason to say exactly 50%. That's stupid. Your starting estimate for probability of such an event happening is really small, so the overconfidence adjustment won't be that large and will likely still keep the probability negligible after the adjustment.
This isn't like cryonics at all. First, the relevant forecast time for cryonics working is a much longer period and it extends much farther into the future than 2018. That means the uncertainty from prediction the future has a much larger impact. Also, people are actively working on the relevant technologies and have clear motivations to do so. I don't in contrast even know what exactly a "super-bomb" is or why someone would feel a need to use it to destroy Arizona.
So the adjustments for predictive uncertainty and general overconfidence should move cryonics a lot closer to 50% than it should for your super-bomb example.
If an American signs up for cryonics and pays their ~$300/year, what are their odds of being revived? Talking to people at LessWrong meetups I've heard estimates of 1 in 2. My friend George Dahl, whose opinion I respect a lot, guesses "less than 1 in 10^6". Niether has given me reasons, those numbers are opaque. My estimate of these odds pretty much determines whether I should sign up. I could afford $300/year, and I would if I thought the odds were 1:2, but not if they were 1:10^6. [1]
In order to see how likely this is to work, we should look at the process. I would sign up with a cryonics company and for life insurance. I'd go on living, enjoying my life and the people around me, paying my annual fees, until some point when I died. After death they would drain my blood, replace it with something that doesn't rupture cell walls when it freezes, freeze me in liquid nitrogen, and leave me there for a long time. At some point, probably after the development of nanotechnology, people would revive me, probably as a computer program.
There's a lot of steps there, and it's easy to see ways they could go wrong. [3] Let's consider some cases and try to get probabilities [4]:
Update: the probabilities below are out of date, and only useful for understanding the comments. I've made a spreadsheet listing both my updated probabilities and those for as many other people as I can find: https://docs.google.com/spreadsheet/...
Combined Probability Of Failure: 99.82%
Odds of success: 1 in 567.
If you can think of other ways cryonics might fail, moving probability mass from "other" to something more quantifiable, that would be helpful. If you think my numbers are off for something, please let me know what a better number would be and why. This is not final.
Am I going about this right? Do people here who think it's rational to sign up for cryonics take a "the payoff is really high, so the small probability doesn't matter" view? Am I overly pessimistic about its chances of success?
Note: I originally posted this on my blog, and the version there has a silly javascript calculator for playing with the probabilities.
[1] To figure out what odds I would accept, I think the right approach is to treat this as if I were considering signing up for something certain and see how much I would pay, then see what odds bring this below $300/year. Even at 1:2 odds this is less effective than Village Reach at averting death [2], so this needs to come out of my 'money spent on me' budget. I think $10,000/year is about the most I'd be willing to spend. It's a lot, but not dying would be pretty nice. This means I'd need odds of 1:33 to sign up.
[2] Counter argument: you should care about quality adjusted life years and not deaths averted. Someone revived maybe should expect to have millenia of life at very high quality. This seems less likely to me than just the claim "will be revived". A lot less likely.
[3] In order to deal with independence issues, all my probability guesses are conditional on everything above them not happening. Each of these things must go right, so this works. For example, society collapsing and my cryonics organization going out of business are very much not independent. So the probability assigned to the latter is the chance that society won't collapse, but my organization goes out of business anyway. This means I can just multiply up the subelements to get probabilities for sections, and then multiply up sections to get an overall probability.
[4] This has a lot in common with the Warren formula, which was inspired by the Drake equation. Robin Hanson also has a breakdown. I also found a breakdown on LessWrong that seems really optimistic.
EDIT 2011-09-26: jsalvatier suggested an online spreadsheet, which is very sensible. Created
EDIT 2011-09-27: I've updated my probabilities some, and made the updates on the spreadsheet.