cousin_it comments on Decision Theories: A Less Wrong Primer - Less Wrong

69 Post author: orthonormal 13 March 2012 11:31PM

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Comment author: gRR 12 March 2012 12:07:38PM *  4 points [-]

Thanks for the recap. It still doesn't answer my question, though:

If X is a causal decision theorist, the choice is clear: whatever Omega decided, it decided already

This appears to be incorrect if the CDT knows that Omega always makes correct predictions

the problem looks much the same if Omega has a 90% success rate rather than 100%.

And this appears to be incorrect in all cases. The right decision depends on exact nature of the noise. If Omega makes the decision by analyzing the agent's psychological tests taken in childhood, then the agent should two-box. And if Omega makes a perfect simulation and then adds random noise, the agent should one-box.

Comment author: cousin_it 12 March 2012 01:29:57PM 1 point [-]

If Omega makes the decision by analyzing the agent's psychological tests taken in childhood, then the agent should two-box.

Sorry, could you explain this in more detail?

Comment author: Gabriel 12 March 2012 03:03:19PM *  7 points [-]

I think the idea is that even if Omega always predicted two-boxing, it still could be said to predict with 90% accuracy if 10% of the human population happened to be one-boxers. And yet you should two-box in that case. So basically, the non-deterministic version of Newcomb's problem isn't specified clearly enough.

Comment author: ksvanhorn 13 March 2012 06:47:23PM 2 points [-]

I disagree. To be at all meaningful to the problem, the "90% accuracy" has to mean that, given all the information available to you, you assign a 90% probability to Omega correctly predicting your choice. This is quite different from correctly predicting the choices of 90% of the human population.

Comment author: drnickbone 13 March 2012 07:37:03PM 0 points [-]

I don't think this works in the example given, where Omega always predicts 2-boxing. We agree that the correct thing to do in that case is to 2-box. And if I've decided to 2-box then I can be > 90% confident that Omega will predict my personal actions correctly. But this still shouldn't make me 1-box.

I've commented on Newcomb in previous threads... in my view it really does matter how Omega makes its predictions, and whether they are perfectly reliable or just very reliable.

Comment author: jimmy 14 March 2012 06:18:16PM *  0 points [-]

Agreed for that case, but perfect reliability still isn't necessary (consider omega 99.99% accurate/10% one boxers for example)

What matters is that your uncertainty in omegas prediction is tied to your uncertainty in your actions. If you're 90% confident that omega gets it right conditioning on deciding to one box and 90% confident that omega gets it right conditional on deciding to two box, then you should one box. (0.9 * 1M>1K+0.1 * 1M)

Comment author: gRR 12 March 2012 03:33:14PM 1 point [-]

Far better explanation than mine, thanks!

Comment author: orthonormal 12 March 2012 04:22:00PM 0 points [-]

Good point. I don't think this is worth going into within this post, but I introduced a weasel word to signify that the circumstances of a 90% Predictor do matter.

Comment author: cousin_it 12 March 2012 03:09:11PM 0 points [-]

Very nice, thanks!

Comment author: gRR 12 March 2012 02:22:08PM *  0 points [-]

Hmm, I'm not sure this is an adequate formalization, but:

Lets assume there is an evolved population of agents. Each agent has an internal parameter p, 0<=p<=1, and implements a decision procedure p*CDT + (1-p)*EDT. That is, given a problem, the agent tosses a pseudorandom p-biased coin and decides according to either CDT or EDT, depending on the results of the toss.

Assume further that there is a test set of a hundred binary decision problems, and Omega knows the test results for every agent, and does not know anything else about them. Then Omega can estimate
P(agent's p = q | test results)
and predict "one box" if the maximum likelihood estimate of p is >1/2 and "two box" otherwise. [Here I assume for the sake of argument that CDT always two-boxes.]

Given a right distribution of p-s in the population, Omega can be made to predict with any given accuracy. Yet, there appears to be no reason to one-box...

Comment author: cousin_it 12 March 2012 02:38:06PM *  0 points [-]

Wait, are you deriving the uselessness of UDT from the fact that the population doesn't contain UDT? That looks circular, unless I'm missing something...

Comment author: gRR 12 March 2012 02:58:03PM *  0 points [-]

Err, no, I'm not deriving the uselessness of either decision theory here. My point is that only the "pure" Newcomb's problem - where Omega always predicts correctly and the agent knows it - is well-defined. The "noisy" problem, where Omega is known to sometimes guess wrong, is underspecified. The correct solution (that is whether one-boxing or two-boxing is the utility maximizing move) depends on exactly how and why Omega makes mistakes. Simply saying "probability 0.9 of correct prediction" is insufficient.

But in the "pure" Newcomb's problem, it seems to me that CDT would actually one-box, reasoning as follows:
1. Since Omega always predicts correctly, I can assume that it makes its predictions using a full simulation.
2. Then this situation in which I find myself now (making the decision in Newcomb's problem) can be either outside or within the simulation. I have no way to know, since it would look the same to me either way.
3. Therefore I should decide assuming 1/2 probability that I am inside Omega's simulation and 1/2 that I am outside.
4. So I one-box.

Comment author: XiXiDu 12 March 2012 02:27:18PM *  0 points [-]

If Omega makes the decision by analyzing the agent's psychological tests taken in childhood, then the agent should two-box.

Sorry, could you explain this in more detail?

Humans are time-inconsistent decision makers. Why would Omega choose to fill the boxes according to a certain point in configuration space rather than some average measure? Most of your life you would have two-boxed after all. Therefore if Omega was to predict whether you (space-time-worm) will take both boxes or not, when it meets you at an arbitrary point in configuration space, it might predict that you are going to two-box if you are not going to life for much longer in which time-period you are going to consistently choose to one-box.

ETA It doesn't really matter when a superintelligence will meet you. What matters is for how long a period you adopted which decision procedure, respectively were susceptible to what kind of exploitation. If you only changed your mind about a decision procedure for .01% of your life it might still worth to act on that acausally.