byrnema comments on Outlawing Anthropics: An Updateless Dilemma - Less Wrong

26 Post author: Eliezer_Yudkowsky 08 September 2009 06:31PM

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Comment author: byrnema 11 September 2009 08:57:59AM *  0 points [-]

Whoohoo! I just figured out the correct way to handle this problem, that renders the global and egocentric/internal reflections consistent.

We will see if my solution makes sense in the morning, but the upshot is that there was/is nothing wrong with the green roomer's posterior, as many people have been correctly defending. The green roomer who computed an EV of $5.60 modeled the money pay-off scheme wrong.

In the incorrect calculation that yields $5.6 EV, the green roomer models himself as winning (getting the favorable +$12) when he is right and losing (paying the -$52) when he is wrong. But no, not exactly. The green roomer doesn't win every time he's right -- even though certainly he's right every time he's right.

The green roomer wins 1 out of every 18 times that he's right, because 17 copies of himself that were also right do not get their own independent winnings, and he loses 1 out of every 2 times he's wrong, because there are 2 of him that are wrong in the room that pays $52.

So it is Bostrom's division-of-responsibility, with the justification. It is probably more apt to name it division-of-reward.

Here's is the correct green roomer calculation:

EV = P(heads)(payoff given heads)(rate of payoff given heads)+ P(tails)(payoff given tails)(rate of payoff given tails)

=.9($12)(1/18)+.1(-$52)(1/2) = -2

(By the way, this doesn't modify what I said about pointers, but I must admit I don't understand at the moment how the two perspectives are related. Yet; some thoughts.)

Comment author: byrnema 11 September 2009 09:13:39AM 0 points [-]

It was 3:30 in the morning just a short while ago, and I woke up with a bunch of non-sensical ideas about the properties of this problem, and then while I was trying to get back to sleep I realized that one of the ideas made sense. Evidence that understanding this problem for myself required a right-brain reboot.

I'm not surprised about the reboot: I've been thinking about this problem a lot, which signals to my brain that it's important, and it literally hurt my brain to think about why the green roomers were losing for the group when they thought they were winning, strongly suggesting I was hitting my apologist limit.