Re: self-sampling assumption is incorrect

From: Russell Standish <>
Date: Sat, 15 Jun 2002 13:59:51 +1000 (EST)

Hal Finney wrote:
> Wei writes:
> > Earlier (at I
> > argued that preference between the two choices is subjective (i.e. depends
> > on your utility function). I now realize this implies that the
> > self-sampling assumption (or SSA, the idea that you should reason as if
> > you were a random sample from the set of all observers, see
> > for more details) cannot be
> > applied universally, because it implies that only choosing the two
> > identical experiences is rational.
> > ...
> What about this variant on the experiment (the full experiment is below).
> Instead of B1 and B2 both getting E1, let B1 get E1 and B2 get E1'.
> E1' is another experience than E1 that is just about as good.
> U(E1) > U(E2) and U(E1') > U(E2). The idea is that this eliminates
> possible issues regarding whether two people (B1 & B2) who get exactly
> the same experience should count twice.
> > Now which strategy I should choose
> > depends on whether U({E1,E1}) > U({E1,E2}), which can be independent of
> > whether U(E1) > U(E2).
> We can change this to whether U({E1,E1'}) > U({E1,E2}) in the modified
> form.
> It does seem that the SSA pretty much implies that if U(E1') > U(E2) then
> U({E1,E1'}) > U({E1,E2}). Is it really rational for this to be otherwise?
> We know that rationality puts some constraints on the utility function.
> We can't have cyclicity in the utility preference graph, for example.
> But in the case above, where U({X,Y}) means the utility of having two
> different independent experiences X and Y, maybe it does follow that
> U({X,Y}) and U({X,Z}) must compare the same as U(Y) and U(Z). You don't
> have any choice but to accept the equivalence. As Lewis Carroll wrote,
> "Then Logic would take you by the throat, and FORCE you to do it!"
> (
> Hal

I find it very hard to see how U({E1,E2}) is anything other than
p(E1)*U(E1)+p(E2)*U(E2) in this sort of experiment.

In the leadup to the discussion, Wei was suggesting that having two
different experiences may be better than repeating the same
experience. Surely this can only be true if you get to keep the first
experience when you experience the second, a situation that is false
in the current setup, since E2 is only experienced if you haven't
experienced E1.

Keep trying, but at this stage the argument against the SSA is not


A/Prof Russell Standish Director
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Received on Fri Jun 14 2002 - 21:04:06 PDT

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