Jack comments on Problematic Problems for TDT - Less Wrong

36 Post author: drnickbone 29 May 2012 03:41PM

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Comment author: ciphergoth 23 May 2012 03:09:44PM *  20 points [-]

Right, but this is exactly the insight of this post put another way. The possibility of an Omega that rewards eg ADT is discussed in Eliezer's TDT paper. He sets out an idea of a "fair" test, which evaluates only what you do and what you are predicted to do, not what you are. What's interesting about this is that this is a "fair" test by that definition, yet it acts like an unfair test.

Because it's a fair test, it doesn't matter whether Omega thinks TDT and TDT-prime are the same - what matters is whether TDT-prime thinks so.

Comment author: Jack 23 May 2012 10:06:14PM 4 points [-]

He sets out an idea of a "fair" test, which evaluates only what you do and what you are predicted to do, not what you are.

Two questions: First, how does is this distinction justified? What a decision theory is is a strategy for responding to decision tasks and simulating agents performing the right decision tasks tells you what kind of decision theory they're using. Why does it matter if it's done implicitly (as in Newcomb's discrimination against CDT) or explicitly. And second why should we care about it? Why is it important for a decision theory to pass fair tests but not unfair tests?

Comment author: APMason 24 May 2012 10:47:29AM 7 points [-]

Why is it important for a decision theory to pass fair tests but not unfair tests?

Well, on unfair tests a decision theory still needs to do as well as possible. If we had a version of the original Newcomb's problem, with the one difference that a CDT agent gets $1billion just for showing up, it's still incumbent upon a TDT agent to walk away with $1000000 rather than $1000. The "unfair" class of problems is that class where "winning as much as possible" is distinct from "winning the most out of all possible agents".

Comment author: ciphergoth 24 May 2012 06:50:28AM 4 points [-]

Real-world unfair tests could matter, though it's not clear if there are any. However, hypothetical unfair tests aren't very informative about what is a good decision theory, because it's trivial to cook one up that favours one theory and disfavours another. I think the hope was to invent a decision theory that does well on all fair tests; the example above seems to show that may not be possible.