Regarding Alan Dean's last contribution:

I wonder if Alan would agree that his discussion implies that there are
limits to (or constraints on :-)) what can emerge and how fast emergence
can proceed.  These limits are physical, chemical and biological.
Because we don't learn everything all at once (itself I imagine a
physical/chemical/biological constraint) there is a limit to the rate at
which we can adapt to changes in the physical or social environment.

Within those limits, cultural norms and institutional arrangements
evolve or coevolve through agent interaction.  Alan did not say, but it
seems compatible with what he did say, that where the culture and
institutiional forms become constraining, the elimination of those
constraints becomes an objective with cultural/institutional changes
consquent upon the constraint-shifting action.  There is plenty of clear
evidence for this sort of constraint-shifting in the history of
technology and business history.

alan also wrote:

> This would seem to suggest that when working with models of natural systems
> care needs to be taken when assigning constraint to different dimensions of
> the system, and when looking for predictable outcomes ..., otherwise the
> simulation may become dysfunctional.
>
I am not sure what he means by dysfunctional in this context.  If he
means that the model is misspecified in the sense that it does not
capture the intended empirical phenomena, then (going back to one of my
earlier points) the limit on the speed of agents' cognitive processes
implies that the features of the institutional/cultural environment that
can be treated as fixed will vary with the length of historical time a
model is intended to capture.  Consequently, it will be essential to
ensure that any comparison of simulation output with real data takes
into account the time interval implied by the choice of fixed
constraints.  I offer this as an example of how care might be taken
"when assigning constraint to different dimensions of the system."

scott

--
Scott Moss                              telephone: +44 (0)161 247 3886
Director                                fax:       +44 (0)161 247 6802
Centre for Policy Modelling
Manchester Metropolitan University
Aytoun Building
Manchester M1 3GH
UNITED KINGDOM

http://www.cpm.mmu.ac.uk/~scott


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