Eliezer_Yudkowsky comments on Expected utility without the independence axiom - Less Wrong

9 Post author: Stuart_Armstrong 28 October 2009 02:40PM

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Comment author: Eliezer_Yudkowsky 29 October 2009 03:24:01AM *  2 points [-]

Is the new axiom sufficient to show that the agent cannot be money-pumped?

Comment author: Stuart_Armstrong 29 October 2009 10:40:18AM *  0 points [-]

It's enough to show that an agent cannot be repeatedly money-pumped. The more opportunities for money pumping, the less chances there are of it succeeding.

Contrast household applicance insurance versus health insurance. Both are a one-shot money-pump, as you get less than your expected utility out of then. An agent following these axioms will probably health-insure, but will not appliance insure.

Comment author: Eliezer_Yudkowsky 29 October 2009 12:28:38PM 2 points [-]

Can you write out the math on that? To me it looks like the Allais Paradox or a simple variant would still go through. It is easy for the expected variance of a bet to increase as a result of learning additional information - in fact the Allais Paradox describes exactly this. So you could prefer A to B when they are bundled with variance-reducing most probable outcome C, and then after C is ruled out by further evidence, prefer B to A. Thus you'd pay a penny at the start to get A rather than B if not-C, and then after learning not-C, pay another penny to get B rather than A.

Comment author: Stuart_Armstrong 29 October 2009 01:00:54PM 1 point [-]

I'll try and do the maths. This is somewhat complex without independence, as you have to estimate what the total results of following a certain strategy is, over all the bets you are likely to face. Obviously you can't money pump me if I know you are going to do it; I just combine all the bets and see it's a money pump, and so don't follow it.

So if you tried to money pump me repeatedly, I'd estimate it was likely that I'd be money pumped, and adjust my strategy accordingly.

Comment author: RobinZ 29 October 2009 03:27:07AM *  0 points [-]

I believe SilasBarta has correctly (if that is the word) noted that it does not - it is perfectly possible for an agent to satisfy the new axioms and fall victim to the Allais Paradox.

Edit: correction - he does not state this.

Comment author: SilasBarta 29 October 2009 03:43:59AM 0 points [-]

That sounds more like the exact opposite of my position.

Comment author: RobinZ 29 October 2009 04:20:09AM 0 points [-]

I apologize. In the course of conversation with you, I came to that conclusion, but you reject that position.

Comment author: SilasBarta 29 October 2009 02:46:36PM 1 point [-]

To summarize my point: if you follow the new axioms, you will act differently in one-shot vs. massive-shot scenarios. Acting like the former in the latter will cause you to be money-pumped, but per the axioms, you never actually do it. So you can follow the new axioms, and still not get money-pumped.