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cousin_it comments on 2013 Survey Results - Less Wrong
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There are (very probably around) 1.7x10^11 galaxies in the observable universe. So I don't understand how can P(Aliens in Milky Way) be so closed to P(Aliens in observable universe)? If P(Aliens in an average galaxy) = 0.0000000001, P(Aliens in observable universe) should be around 1-(1-0.0000000001)^(1.7x10^11)=0.9999999586. I know there are other factors that influence these numbers, but still, even if there's a only a very slight chance for P(Aliens in Milky Way), then P(Aliens in observable universe) should be almost certain. There are possible rational justifications for the results of this survey, but I think (0.95) most people were victim of a cognitive bias. Scope insensitivity maybe? because 1.7*10^11 galaxies is too big to imagine. What do you think?
I wonder how many people cooperated only (or in part) because they knew the results would be correlated with their (political) views, and they wanted their "tribe"/community/group/etc. to look good. Maybe next year we could say that this result won't be compared to the other? So if less people cooperate, then it will indicate that maybe some people cooperate for their 'group' to look good. But if these people know that I/we want to compare the results we this year in order to verify this hypothesis, they will continue to cooperate. To avoid most of these, we should compare only the people that will have filled the survey for the first time next year. What do you think?
I think you shouldn't have corrected anything. When I assign a probability to the correctness of my answer, I included a percentage for having misread the question or made a data entry error.
Would some people be interested in answering 10 such questions and give their confidence about their answer every month? That would provide better statistics and a way to see if we're improving.
Only if our uncertainties about the different galaxies are independent, and don't depend on a common uncertainty about the laws of nature or something. It's true that P2>P1, but they can be made arbitrarily close, I think.
I agree. But I don't think they can be that strongly dependant (not even close). How could they be?
One way would be for most of the expectation of aliens to come from expectation that the Fermi Paradox is somehow illusionary. There are probably other ways, but I can't think of any at the moment.
Toy example:
Suppose that your credence in "aliens in an average galaxy" is split across 2 distinct hypotheses:
A. Life is very common across the universe, but for some reason we can't detect it. (with confidence 10^-4)
B. Life is not common, but any given galaxy has a 10^-16 chance to develop life.
Total confidence that alien life exists in any given galaxy: ~10^-4.
So your confidence in "aliens exist in the observable universe" is likewise split:
A. Life is very common across the universe, but for some reason we can't detect it. (with confidence 10^-4)
B. Life is not common, but 1.7*10^11 galaxies means a chance of 1-(1-10^-16)^(1.7*10^11) = ~10^-5
Total confidence that life exists in the observable universe: ~10^-4.
EDIT 3: I retract the following paragraph because I now understand what Wes_W wrote.
I know, that's why I said "There are possible rational justifications". I mean your reasoning make sense mathematically. But why would your distribution be two deltas at 10^-4 and 10^-16 and not more continuous? It's not a rhetorical question, I want to know the answer -if there's one-, but I don't see how it could be that way. Do you think you are rationalizing your answer? (again, it's not a rhetorical question)
EDIT: After reading other comments, I think another way a discontinuity might be justify is like this: going faster than light speed is either possible or not.
A. if it is, then if there's a sufficiently advance civilisation (anywhere in the Observable Universe) it would probably be able to colonize most of the(ir) observable universe. (so the probability that there are aliens in the Milky Way is similar to the Observable Universe).
B. if it isn't, then it's the probability that there are aliens in the Milky Way is a lot lower than in the Observable Universe.
EDIT 2: Can you think of other reasons for the discontinuity? With what probability do you think the speed of light is the maximum speed one can transfer information/energy?
I don't think I'm rationalizing an answer; I'm not even presenting an answer. I meant only to present a (very simplified) example of how such a conclusion might arise.
I'm totally willing to chalk the survey results up to scale insensitivity, but such results aren't necessarily nonsensical. It could just mean somebody started with "what credence do I assign that aliens exist and the Fermi Paradox is/isn't an illusion" and worked backwards from there, rather than pulling a number out of thin air for "chance of life developing in a single galaxy" and then exponentiating.
Since the latter method gives sharply differing results depending on whether you make up a probability a few orders of magnitude above or below 10^-11, I'm not sure working backwards is even a worse idea. At least working backwards won't give one 99.99999% credence in something merely because their brain is bad at intuitively telling apart 10^-8 and 10^-14.
Edit: I think some degree of dichotomy is plausible here. A lot of intermediate estimates are ruled out by us not seeing aliens everywhere.
Sorry I misunderstood. (Oops) I agree (see my edits in the previous comment). A justify dichotomy is more probable than I initially thought, and probably less people made a scale insensitivity bias than I initially thought.
Because it's a toy example and it's easier to work out the math this way. You can get similar results with more continuous distributions, the math is simply more complicated.
Ok right. I agree.
There's two sorts of uncertainty here. The more physical kind: probability that life arises, intelligence evolves, etc etc.
And there's "our uncertainty" kind of probability - we don't know what it takes for the life to evolve - and this is common for all galaxies.