Re: The Conjunction Fallacy Fallacy [WAS Re: Anti-singularity spam.]

From: Eliezer S. Yudkowsky (
Date: Fri Aug 25 2006 - 15:11:53 MDT

Richard Loosemore wrote:
> Eliezer S. Yudkowsky wrote:
>> Richard Loosemore wrote:
>>> Thus, in common-or-garden nontechnical discourse, the question:
>>> Which of the following is more probable:
>>> 1) Linda is a bank teller and is active in the feminist movement.
>>> 2) Linda is a bank teller.
>>> Would quite likely be interpreted as
>>> Which of the following is more probable:
>>> 1) Linda is a bank teller and is active in the feminist movement.
>>> 2) Linda is a bank teller and NOT active in the feminist movement.
>> Old, old, old alternative hypothesis disconfirmed a dozen ways from
>> Tuesday. I was very quickly summarizing an extensive literature with
>> thousands of papers. These are not my ideas, these are the mainstream
>> conclusions of an experimental science. Go forth and read the
>> literature before you make up your own interpretations. I suggest
>> starting with "Judgment Under Uncertainty" and moving on to
>> "Heuristics and Biases".
> You just attacked an argument that has nothing whatsoever to do with the
> claim that I actually made.

Well, let's see. For one thing, it flatly demonstrates that you're not
familiar with the literature. So does your statement here:

> So in the case of the above experiment, I had forgotten the punchline of the experiment, so I looked at it and did it on the spot.
> Hey presto: my first answer was (2)!
> Why? Because, even though I had been primed by all the Conjunction
> Fallacy stuff in the last week, I completely forgot to notice that the
> the first string was shorter than the other two (perhaps because all the
> RRRR strings misled my eye, in the way that you may, depending on your
> mail client, have had your own eye misled earlier in this sentence). And
> on the other hand I did notice (because I had been primed by the only
> relevant information given in the instructions) that there were
> differences between the proportions of Gs and Rs in the three strings.
> I was also rushing because I felt some urgency to prove to myself that I
> could polish it off quickly.
> Well well well. I am stupid and irrational, apparently! And there is no other explanation for my (or the subjects') behavior: it really cannot be anything except irrational stupidity.

This is, simply put, exactly the standard experimental result *and its
standard interpretation*: subjects substitute judgment of
representativeness for judgment of probability.

You noticed differences between the proportions of Gs and Rs in the
three strings? That's called, "judgment by representativeness" or "the
representativeness heuristic". In a nutshell.

You could not possibly fail to recognize this if you had absorbed any
substantial amount of literature on heuristics and biases. It'll be in
the first chapters of any work on the subject.

> Specifically, there are two interpretations of their role:
> 1) The interfering mechanisms were just dumb, maladaptive strategies.
> Basically, systematic biasses and mistakes.
> 2) These other mechanisms were not just systematic biasses, but may
> actually have been components of very powerful, sensible, adaptive
> cognitive mechanisms that do not use logical reasoning, and without
> which the system as a whole could not function. A number of people have
> arguments that are equal or closely related to this point, so
> Interpretation (1) is the default assumption in the literature. To the
> extent that the literature looked at what was going on in these
> experiments, it tended to treat the situation as one of rationality
> corrupted by mistakes.

The standard approach is that biases can shed light on our actual
reasoning methods, the heuristics, that are producing the mistakes.

Judgment by representativeness, like judgment by availability, is a
heuristic that can often produce useful results - some even say a fast
and frugal heuristic - but the heuristic also produces systematic
biases, which are what reveal to us that the heuristic exists in the
first place, and what pin down how the heuristic must be working to
produce those specific biases.

The field that emphasizes the evolutionary rationale of heuristics would
be the "fast and frugal" crowd. (There is no sign that Loosemore is
familiar with this paradigm, either.)

> You say that your analysis represents the "mainstream conclusions of an
> experimental science". And you tell me that I should "Go forth and read
> the literature before [I] make up [my] own interpretations". You think
> I just made up my own interpretations? I have had extensive discussions
> about these and other issues with people like Mike Oaksford (he and I
> were at UCNW Bangor together, then at Warwick), and to a lesser extent
> with Nick Chater. I have also benefitted from many discussions with Tom
> Ormerod, who does experimental work in the same field. In 1987 I did an
> extensive analysis of Phil Johnson-Laird's work, and although I never
> got to challenge him in person, I did talk to Alan Garnham, one of his
> students, and got a great deal of agreement from him about my
> understanding of the issues and my specific criticisms of J-L.
> Strangely, Oaksford and Chater disagree with your analysis, as do Evans
> and Over. From my limited understanding of them, Maule and Hodgkinson
> (2002), and Tetlock and Mellers (2002) would also be in sympathy with
> the position I just took. As would many others that I have talked with
> over the years, who do not work directly in this area. Given all of
> this, it hardly sounds like you presented the mainstream conclusions of
> an experimental science.

I sampled two of these names, Mike Oaksford and Phil Johnson-Laird. I
didn't hit any papers in the field of heuristics and biases. I see no
evidence that they have ever worked in the field of heuristics and
biases. I did see papers on the construction of mental models, which,
if you happened to be completely unfamiliar with the field of heuristics
and biases, could be mistaken for information relevant to interpreting
the Linda experiment.

I did, indeed, present the mainstream conclusions of an experimental
science. Which, it seems, Richard has never heard of. He is not even
aware of who works in the field and who does not; he does not know
*which* field I am talking about.

I won't say that Richard was "bluffing" - since he has no idea the field
of heuristics and biases exists, he has no idea that his distantly
related reading about other things, is not knowledge of that field. But
he is still rather ignorant and rather unaware of it.

My original email reply to his first message still says all that needed
to be said: RTFM! (To name a specific M, "Judgment Under Uncertainty"
would do him some good.)

Eliezer S. Yudkowsky                
Research Fellow, Singularity Institute for Artificial Intelligence

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