Re: Criticisms and defense of ABM

[Paul Johnson]

Hey, Paul. I have some experience with this too!

Paul Charteris wrote:
> Dear Swarm Modelling Group
>
> Yesterday I gave a rather informal seminar on the use of agent-based 
> modeling to the animal genetics group at Colorado State University and 
> (not unexpectedly) received a couple of criticisms - especially from my 
> Ph.D. major advisor. Anyway, the two main criticisms that I attempted to 
> defend myself against were:
>
> Criticism 1. One of my dissertation objectives is stated in this way: 
> "To explore the utility of Agent-Based Models in describing the 
> industry-level outcome of breeding decisions made by individual 
> enterprises" As a note, these breeding technologies are animal genetic 
> technologies that allow farmers to make more accurate genetic selection 
> decisions.
>
> Their view - The aim of assessing whether a methodology is appropriate 
> to a problem is not a suitable research objective in its own right, i.e. 
> the study should not undertake simulation for the sake of determining if 
> simulation works.

I think you have a "disciplinary boundary" issue here. For a person in 
computer science or whose training is mostly about research methodology, 
then exploring the suitability of the approach would be an acceptable 
topic, especially if suitability had a rigorous definition.  If your 
main area of study is methodology, you could make your case by 
investigating two models of the same thing. One ABM model, one game 
theory, or whatever.

On the other hand, if your training is substantive in nature, then 
perhaps it is not the right question to ask.  Your advisors may fear 
that you will lose track of your focus on animals when you launch off in 
to the simulation world. I know they fear that because I fear it, both 
for myself and my students.
> Criticism 2 - All agent-based modeling is essentially prediction.
>
> Their view - any outcomes of an agent-based model are a prediction of 
> entities or processes in the system. Prediction can be thought of as any 
> declaration or estimate regarding the future.
I think they are making a a silly point here. All theories, whether they 
are represented as differential equations, game theory, or ABM, have 
both assumptions and structures (the "explanatory" part) as well as some 
predictive statements about outcomes.

In social science, we strive for theories that let us compare outcomes 
under different conditions (comparative statics or dynamics).  Any 
theory has to have some implications for outcomes, even if it is such a 
weak statement as "anything can happen under conditions X".  The ABM is 
no different.

In political science, my contention has been that ABMs don't help you 
get deeper insight into individual behavior, but rather they help you 
explore the impact of institutions and environment.  One can imagine 
life under alternative constitutions or with different decision making 
rules.

I think there is a growing literature to which you could refer your 
advisors.  There was a great paper 2 swarm fests ago presented by John 
Pepper. It was animal foraging behavior on a patchy landscape.

I think your advisors are correct in that the answer to the question 
"does my ABM match up well with reality" is hard to answer and often 
requires somewhat dubious comparisons of predictions against observed 
data, though.


> My view - No the aim of agent-based modeling is frequently not a 
> declaration or estimate of the future but frequently relates to 
> observing the processes that lead to some future outcome. They argue 
> that observing these processes is prediction in its own right. I 
> counter-argued that we do not make a declaration or estimate of these 
> processes at all- rather we simply parameterize the agents in their own 
> model world and hope some "goodies" come out of the model. I guess the 
> point is subtle, we (the modeler) do not try and anticipate the future - 
> we only parameterize the present and observe what possible futures may 
> exist. Maybe this is an estimate of the future after all?
>
> Any thoughts or comments on these points of view would be most welcome.
>
> Cheers, Paul Charteris


--
Paul E. Johnson                       email: address@hidden
Dept. of Political Science            http://lark.cc.ku.edu/~pauljohn
University of Kansas                  Office: (785) 864-9086
Lawrence, Kansas 66045                FAX: (785) 864-5700



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