# Oscar_Cunningham comments on Utility is unintuitive - Less Wrong Discussion

-6 09 December 2010 05:39AM

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Comment author: 09 December 2010 11:22:04PM 2 points [-]

Utils aren't just another form of currency. They're a currency that we've adjusted the value of so that we're exactly twice as happy with two utils than with one. Hence if the 1000 utils range is contentment, the 100 utils range can't possibly really really suck, instead it's exactly 10 times worse than contentment.

Comment author: 09 December 2010 11:27:52PM 4 points [-]

Thinking about them as a currency is in general misleading, since they're not fungible - what is worth 1 util to you isn't necessarily worth 1 util to anyone else.

Comment author: 10 December 2010 03:01:06AM 1 point [-]

I understand that part, as far as it goes.

So, by definition, if I'm content with 1000 utils, then given 100 utils I'm a tenth of content. (Cononet?) And being cononet is, again by definition, not bad enough that a 99% chance of it is something I could rationally choose to avoid, even if it meant giving up a 1% chance at being gloriously conthousandt.

Well, OK, if y'all say so. But I don't understand where those quantitative judgments are coming from.

Put another way: if the range I'm in right now is 1000 utils, and I want to estimate what range I was in during the month after my stroke, when things really really sucked... a state that I would not willingly accept a 99% chance of returning to... well, how do I estimate that?

I mean, I understand that 100 is too high a number, though I don't know how you calculated that, but what is the right number? 10? 1? -100? -10000? What equations apply?

Comment author: 10 December 2010 03:19:34AM 2 points [-]

Imagine this bet: If you win, you'll get to a point that is twice as good as the one you're at right now: 2000 utils. If you lose, you'll be at a point that sucked as much as that post-stroke month. What would the probabilty of winning have to be for you to be indifferent to this bet?

The utility of the awful state is then x in the equation 2000P(w) + x(1 - P(w)) = 1000, where P(w) is the probability of winning.

If x were 100, the bet would be worth taking if it offered odds better than 9 in 19. If you wouldn't take that bet, x is lower. On this scale, I suspect your utility for x is very, very far below 0.

Comment author: 10 December 2010 03:45:53AM 3 points [-]

OK... that question at least makes sense to me. Thank you.

Hm. Would I take, say, a 50% bet along those lines? I flip a coin, heads I have another stroke, tails things suddenly get as much better than they are now as now is better than then. Nope, I don't take that bet.

A 25% chance? Hm.

No, I don't take that bet.

A 5% chance? Hmmmmmmmm... that is tempting. And I'll probably always wonder what-if. But no, I don't think I take that bet.

A 1% chance? Yeah, OK. I probably take that bet.

So P(w) is somewhere between .01 and .05; probably closer to .01. Call it .015.

I think what I've probably just demonstrated is that I'm subject to cognitive biases involving small percentage chances... I think my mind is just rounding 1% to "close enough to zero as makes no difference."

But, OK, I guess utils can measure biased preferences as well as rational ones. All that matters is that it's my preference, right, not why it's my preference.

So, all right. 2000P(w) + x(1 - P(w)) = 1000 => 2000(.015) + x(1 - .015) = 1000 => 30 + .985x = 1000 => x=(1000-30)/.985 = ~985.

OK, cool. So my current condition is 1000 util, and my stroke condition (which really really sucks) is 985 utils.

What does that tell us?

Comment author: 10 December 2010 04:14:56AM 2 points [-]

You got your numbers flipped. P(w) is your chance of winning. You want

2000(.985) + x(1 - .985) = 1000 => 1970 + .015x = 1000 => x = (1000-1970)/.015 = -64,666.66...

That tells you that you really don't want to have another stroke. Which is hopefully unsurprising.

Comment author: 10 December 2010 04:21:10AM 2 points [-]

Ah! That makes far more sense. (That number seemed really implausible, but after triple-checking my math I shrugged my shoulders and went with it.)

OK. So, it no longer seems nearly so plausible that I'd turn down the original bet... it really does help me to have something concrete to attach these numbers to. Thanks.

And, yeah, that is profoundly unsurprising.

Comment author: 10 December 2010 01:20:25PM 0 points [-]

You offered me a series of bets about "twice as good as the one you're at right now: 2000 utils" vs "a point that sucked as much as that post-stroke month". I interpreted that as "I have another stroke" vs. "things suddenly get as much better than they are now as now is better than then" and evaluated those bets based on that interpretation.

But that was a false interpretation, and my results are internally inconsistent. If how-things-were-then is -64.5K, then 2000 is not as much better than they are now as now is better than then... they are merely 1/65th better. In which case I don't accept that bet, after all... a 1% chance of another stroke vs a 99% chance of a 1/65th improvement in my life is not nearly as compelling.

More generally, I accepted the initial statement that the state we labeled 2000 is "twice as good as" the state we labeled 1000, because that seemed to make sense when we were talking about numbers. But now that I'm trying to actually map those numbers to something, it's less clear to me that it makes sense.

I mean, it follows that my stroke was "-64 times worse" than how things are now, and... well, what does that even mean?

Sorry... I'm not trying to be a pedant here, I'm just trying to make sure I actually understand what we're talking about, and it's pretty clear that I don't.

Comment author: 17 January 2011 09:59:16PM *  1 point [-]

Yeah, the notion of "twice as good as things are now" doesn't actually make sense, because utility is only defined up to affine transformations. (That is, if you decided to raise your utility for every outcome by 1000, you'd make the same decisions afterward as you did before; it's the relative distances that matter, not the scaling or the place you call 0. It's rather like the Fahrenheit and Celsius scales for temperature.)

But anyway, you can figure out the relative distances in the same way; call what you have right now 1000, imagine some particular awesome scenario and call that 2000, and then figure out the utility of having another stroke, relative to that. For any plausible scenario (excluding things that could only happen post-Singularity), you should wind up again with an extremely negative (but not ridiculous) number for a stroke.

On the other hand, conscious introspection is a very poor tool for figuring out our relative utilities (to the degree that our decisions can be said to flow from a utility function at all!), because of signaling reasons in particular.

Comment author: 17 January 2011 11:51:57PM 0 points [-]

conscious introspection is a very poor tool for figuring out our relative utilities

Certainly. Or, really, much of anything else. Is there a better tool available in this case?

Comment author: 18 January 2011 06:16:34AM 0 points [-]

Not that I know of. Just a warning not to be too certain of the results you get from this algorithm- your extrapolations to actual decisions may be far from what you'd actually do.

Comment author: 10 December 2010 10:07:12AM 0 points [-]

I think what I've probably just demonstrated is that I'm subject to cognitive biases involving small percentage chances... I think my mind is just rounding 1% to "close enough to zero as makes no difference."

Maybe, but I find it easier to fall for the opposite bias, the one known as "There's still a chance, right?"

Comment author: 10 December 2010 07:31:46PM 3 points [-]

(nods) Sadly, my succeptability to rounding very small probabilities up when I want them to be true is not inversely correlated with my succeptability to rounding very small probabilities down when I want to ignore them. Ain't motivated cognition grand?

I do find that I can subvert both of these failure modes by switching scales, though. That is, if I start thinking in "permil" rather than percent, all of a sudden a 1% chance (that is, a 10 permil chance) stops seeming quite so negligible.

Comment author: 17 January 2011 10:02:16PM 0 points [-]

if I start thinking in "permil" rather than percent, all of a sudden a 1% chance (that is, a 10 permil chance) stops seeming quite so negligible.

Huh, that's a pretty neat hack!