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Dorikka comments on Can anyone explain to me why CDT two-boxes? - Less Wrong Discussion

-12 Post author: Andreas_Giger 02 July 2012 06:06AM

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Comment author: Dorikka 02 July 2012 12:34:30PM 1 point [-]

It seems like if you haven't understood what's going on in a problem until very recently, when people explained it to you, and then you've come up with an answer to the problem that most people familiar with the subject material are objecting to.

How high is the prior for your hypothesis, that your posterior is still high after so much evidence pointing the other way?

Comment author: Andreas_Giger comment score below threshold [+] (14 children)

Comment author: JonathanLivengood 02 July 2012 07:07:19PM 4 points [-]

The claim that actual Newcomb or something suitably close cannot exist in reality is very strong. I wonder how you propose to think about research by Haynes et al. (pdf), which suggests that yes/no decisions may be predicted from brain states as long as 7-10 seconds before the decision is made and with accuracy ranging from 54% to 59% depending on the brain region used (assuming I'm reading their Supplementary Figure 6 correctly). In Newcomb's problem, the predictor doesn't need to do much better than chance in order for two-boxing to have lower expectation than one-boxing; in particular, the accuracy obtained by Haynes et al. is good enough.

So ... do you really mean to say that it is impossible that the sort of predictions Haynes et al. make could be done in real time in advance of the choice that a person makes in a Newcomb problem?

Comment author: Andreas_Giger 02 July 2012 08:59:46PM * -1 points [-]

Huh? It's not as if my current brain state was influenced by a decision I'm going to make in ten seconds; it's the decision I make right now that is influenced by my brain state from 10 seconds ago.

So I don't see your point; a good friend of mine could make a far more accurate prediction than 60%. Hell, you could.

Comment author: JonathanLivengood 02 July 2012 09:13:30PM 1 point [-]

Then let me just re-iterate, I don't see what about Newcomb you think is impossible.

The Newcomb set-up is just the following:

Predictor tells you that you are going to play a game in which you pick one box or two. Predictor tells you the payouts for those choices under two scenarios: (1) that Predictor predicts you will choose one box and (2) that Predictor predicts you will choose two boxes. Predictor also tells you its success rate (or you are allowed to learn this empirically). Predictor then looks at something about you (behavior, brain states, writings, whatever) and predicts whether you will take one box or two boxes. After the prediction is made and the payouts determined, you make your decision.

Indeed, your decision now does not affect your brain states in the past. Nor does your decision now affect Predictor's prediction, though your past brain states might depending on how the scenario is realized. And that's kind of the whole point. What you decide now doesn't affect the payouts. So, for CDT, you should take both boxes.

Notice, though, that the problem is not pressing unless the expected value of choosing one box is greater than the expected value of choosing two boxes. That is, the problem is not pressing if Predictor's accuracy is too low.

Now, you have been claiming that Newcomb is impossible. But in your comment here, you seem to be saying that it is really easy to set up. So, I don't know what you are trying to say cannot exist.

Comment author: Alejandro1 03 July 2012 12:22:10AM 0 points [-]

Predictor tells you that you are going to play a game in which you pick one box or two. Predictor tells you the payouts for those choices under two scenarios: (1) that Predictor predicts you will choose one box and (2) that Predictor predicts you will choose two boxes. Predictor also tells you its success rate (or you are allowed to learn this empirically). Predictor then looks at something about you (behavior, brain states, writings, whatever) and predicts whether you will take one box or two boxes. After the prediction is made and the payouts determined, you make your decision.

I prefer the formulation in which Predictor first looks at something about you (without you knowing), makes its prediction and sets the boxes, then presents you with the boxes and tells you the rules of the game (and ideally, you have never heard of it before). Your setting allows you to sidestep the thorny issues peculiar to Newcomb if you have strong enough pre-commitment faculties.

Comment author: JonathanLivengood 03 July 2012 01:12:05AM 1 point [-]

Both ways of setting it up allow pre-commitment solutions. The fact that one might not have thought about such solutions in time to implement them is not relevant to the question of which decision theory one ought to implement.

Why do you think it matters whether you have heard of the game before or whether you know that Predictor (Omega ... whatever) is looking?

I admit that your way of setting it up makes a Haynes-style realization of the problem unlikely. But so what? My way of setting it up is still a Newcomb problem. It has every bit of logical / decision theoretical force as your way of setting it up. The point of the problem is to test decision theories. CDT (without pre-commitment) is going to take two boxes on your set-up and also on mine. And that should be enough to say that Newcomb problems are possible. (Nomologically possible, not just metaphysically possible or logically possible.)

Comment author: Alejandro1 03 July 2012 09:27:53PM 0 points [-]

What I meant was simply this: if I am told of the rules first, before the prediction is made, and I am capable of precommitment (by which I mean binding my future self to do in the future what I choose for it now) then I can win with CDT. I can reason "if I commit to one-box, Omega will predict I will one-box, so the money will be there", which is a kind of reasoning CDT allows. I thought the whole point of Newcombe is to give an example where CDT loses and we are forced to use a more sophisticated theory.

I am puzzled by you saying "Both ways of setting it up allow pre-commitment solutions." If I have never heard of the problem before being presented with the boxes, then how can I precommit?

I confess I thought this was obvious, so the fact that both you and Dave jumped on my statement makes me suspect we have some miscommunication, or that I have some "unknown unknown" misconception on these issues.

Comment author: TheOtherDave 03 July 2012 10:00:43PM 1 point [-]

I agree that if I know the rules, I can reason "if I commit to one-box, Omega will predict I will one-box, so the money will be there", and if I don't know the rules, I can't reason that way (since I can't know the relationship between one-boxing and money).

It seems to me that if I don't know the rules, I can similarly reason "if I commit to doing whatever I can do that gets me the most money, then Omega will predict that I will do whatever I can do that gets me the most money. If Omega sets up the rules such that I believe doing X gets me the most money, and I can do X, then Omega will predict that I will do X, and will act accordingly. In the standard formulation, unpredictably two-boxing gets me the most money, but because Omega is a superior predictor I can't unpredictably two-box. Predictably one-boxing gets me the second-most money. Because of my precommitment, Omega will predict that upon being informed of the rules I will one-box, and the money will be there. "

Now, I'm no kind of decision theory expert, so maybe there's something about CDT that precludes reasoning in this way. So much the worse for CDT if so, since this seems like an entirely straightforward way to reason.

Incidentally, I don't agree to the connotations of "jumped on."

Comment author: Alejandro1 03 July 2012 10:15:39PM * 0 points [-]

Checking the definition, it seems that "jump on" is more negative that I thought it was. I just meant both of you disagreed in similar way and fairly quickly; I didn't feel reprimanded or attacked.

I do not understand at all the reasoning that follows "if I don't know the rules". If you are presented with the two boxes out of the blue and explained the rules then for the first time, there is no commitment to make (you have to decide in the moment) and the prediction has been made before, not after.

continue this thread »

Comment author: JonathanLivengood 03 July 2012 11:14:32PM 0 points [-]

I agree with what Dave says in his comment, which is basically that you could have a very generic pre-commitment strategy.

But suppose you couldn't come up with a very generic pre-commitment strategy or that it is really implausible that you could come up with a pre-commitment solution at all before hearing the rules of the game. Would that mean that there are no pre-commitment solutions? No. You've already identified a pre-commitment solution. We only seem to disagree about how important it is that the reasoner be able to discover a pre-commitment solution quickly enough to implement it.

What I am saying is that the logic of the problem does not depend on the reasoning capacity of the agent involved. Good reasoning is good reasoning whether the agent can carry it out or not.

Also, sorry if I jumped too hard.

Comment author: TheOtherDave 03 July 2012 01:41:40AM 0 points [-]

Can you expand on the difference here?

If I have a "strong enough" precommitment to do whatever gets me the most money, and Predictor privately sets the payoffs for (1box, 2box) such that 1box > 2box, then Predictor can predict that upon being told the payoffs, I will 1box, and Predictor will therefore set the boxes as for the 1box scenario. Conversely, if Predictor privately sets the payoffs such that 2boxing gets me the most money, then Predictor can predict that upon being told the payoffs I'll 2box.

So what thorny issues does this delayed specification of the rules prevent me from sidestepping?

Comment author: Alejandro1 03 July 2012 09:28:04PM 0 points [-]

See my response to Jonathan.

Dorikka comments on Can anyone explain to me why CDT two-boxes? - Less Wrong Discussion

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