Robert,
===>Robert Holmes wrote:<===
==>Schelling's segregation model is completely misrepresented. The notion that
segregation decreases as the individuals' desire to be segregated increases is
wrong. Nick - have a play with the Netlogo model! As you increase the
"%-similar-wanted" slider, the end-point of the "percent-similar" plot get
closer to 100%<===
I DID play with the model! Although you are the last person I would want to go
up against on such a geek matter, I think it performs pretty much as the paper
describes. In fact, I have it running at this very moment. Percent similar
sought is set to 85, average percent similar achieved is running around 50
percent and everybody is unhappy. There is, I think, a dramatic phase change
between 70 percent sought and 80 percent sought, in fact, now that I explore
it, between 75 and 76%.
Steve, and others: I wonder if this is not a case where increasing the
gradient actually DECREASES the structure?
===>Hempels' symmetry of explanation and prediction has been dead and buried
for years so really can't be used to support any argument; <===
I think the paper puts it around the other way: that scientific practice
supports Hempel, not other way around. "Precisely the same point holds for the
other examples—which, collectively, serve to confirm, not undermine, Carl
Hempel's sixty-year old "Symmetry Thesis" concerning explanatory and predictive
power (Hempel 1948)."Can you think of any examples of good scientific theories
that do not provide good, clear, expectations of observation?
===>hypothesizing micro-rules in models is actually a perfectly reasonable
thing to do;<===
I think I agree; where do Derr and I contradict this assertion?
===>the burden-of-proof should rest with the modeler, not with anyone who dares
to disagree with her.<===
Again, not clear what you have in mind, here, or how it stands in contradiction
to Derr and Thompson.
Thanks for the comments,
Nick
Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology,
Clark University ([email protected])
----- Original Message -----
From: Robert Holmes
To: The Friday Morning Applied Complexity Coffee Group
Sent: 2/1/2009 1:20:35 PM
Subject: [FRIAM] Contra Thompson: problems with the explanation ofexplanations
Although I agree with the overall tenor of Nick's "Contra Epstein" piece
(http://jasss.soc.surrey.ac.uk/12/1/9.html), there's one glaring error:
Schelling's segregation model is completely misrepresented. The notion that
segregation decreases as the individuals' desire to be segregated increases is
wrong. Nick - have a play with the Netlogo model! As you increase the
"%-similar-wanted" slider, the end-point of the "percent-similar" plot get
closer to 100%. It does NOT suddenly start dropping. The interesting point that
the model illuminates is that you need surprisingly low values of
"%-similar-wanted" to generate high "percent similar" environments.
Robert
P.S. There's some other parts of the paper I'd argue with, viz:
Hempels' symmetry of explanation and prediction has been dead and buried for
years so really can't be used to support any argument;
hypothesizing micro-rules in models is actually a perfectly reasonable thing to
do;
the burden-of-proof should rest with the modeler, not with anyone who dares to
disagree with her.
...but having already demolished 40% of Nick's paper, I thought I'd better give
it a rest :-) Nick - buy me a coffee and I'll give you details!
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