Biology 361 = Computer Science 361
Bryn Mawr College
Spring 2006

Agent Based Modelling
V. Beyond "Simple" Agents and Environments ... ?

Paul Grobstein
20, 22 February 2006

Last week's assignment:

Do some more learning about/playing with Netlogo models. What is, is not gained by increased model complexity? What additional complexities might one want to introduce, why? And a little reflecting on where we've been, might go ...

Some Blog Thoughts

When I think of emergence, I feel like I have to "change my glasses" (not that I wear them) and put on something that makes the world fresh again. Something that gives me back that sense of wonder that we all had when we were children. ... Julia_Ferraioli

As unreliable as our minds (and sensory perceptions and concepts of reality) might be, I figure this idea of trying on different perspectives whenever possible is a good way to guard against complacency and self-deception ... Kathy Maffei

I have been troubled by the idea that in making computer models, our objective "is to be 'surprised', to 'surprise' others, to establish that some pattern/phenomenon that is presumed to depend on complexity/planning/a directive element can be produced without that. To show what might be, rather than what is." This has been a recurring theme in lecture and it just does not sit well with me. Why is it that models cannot be used to solve problems? Why don't they portray what is? ... If the modeling method has no utility beyond surprise, then it is little more than an intellectual jack in the box ... aren't models also used as a tool to extend the possibilities of thought? ... the importance of the surprise seems to me overshadowed by the importance of its implications ... FloraShepherd

I think the study of emergence shows that when you have sufficiently interesting interacting agents, then the system will undoubtedly have surprises ... DougBlank

I very much agree with you that the point of modelling is "to extend the possibilities of thought". "Surprise", as I meant the term, is the signal that such a thing might in fact happen. And, I agree, worthwhile if and only if it is in fact used to do that ... PaulGrobstein

I noticed that all of the books appear to be written by white men ... Flora Shepherd

Here is the model with two of Langton's ants ... LeslieMcTabish

Why are we surprised? What have we presumed that we need to rethink? In what way does the observation require us to "extend the possibilities of thoughts"? What new observations do we need?

I thought that even if we only consider two colors of people, we should still probably consider the fact that in real life there isn't often an equal number of each. It seems as though it would be useful to be able to adjust the proportion of color quantities (and so there's an enhancement suggestion). ... KathyMaffei

I wholeheartedly agree with you--though the segregation model does do a good job of keeping things simple, it almost oversimplifies the problem by leaving out some parameters central to the question of segregation ... BenKoski

What I'm trying to get at is this: how do we know that our understanding is complete? How do we know that there isn't more math out there that we haven't discovered? What if that math transcends human thought? ... This leads me to the bane of my existence: the idea of "randomness" ... Sunny Singh

The digits of pi are definitely not random; considering that there are formulae that return the nth digit of pi where n is any real number. I am no mathematician, but my problem with that movie's portrayal of this kind of research is that patterns in the digits of pi are meaningless, because like any PSEUDO-random number, or large enough body of information, it is possible to find any conceivable pattern if you look hard enough ... DavidRosen

I'm less disturbed by the idea of randomness, though. Like I said before, I think randomness might give us the philosophical wiggle-room for free will in what might otherwise appear to be a deterministic system ... But then again, I'm not disturbed by the idea that the universe is deterministic ... I was satisfied with Doug's comment on this in class (please forgive the paraphrase): does it really matter, since we can't tell the difference? ... Kathy Maffei

" ... science itself will teach man (though to my mind it's a superfluous luxury) that he never has really had any caprice or will of his own, and that he himself is something of the nature of a piano-key or the stop of an organ, and that there are, besides, things called the laws of nature; so that everything he does is not done by his willing it, but is done of itself, by the laws of nature. Consequently we have only to discover these laws of nature, and man will no longer have to answer for his actions and life will become exceedingly easy for him.

... even if man really were nothing but a piano-key, even if this were proved to him by natural science and mathematics, even then he would not become reasonable, but would purposely do something perverse out of simple ingratitude, simply to gain his point. And if he does not find means he will contrive destruction and chaos, will contrive sufferings of all sorts, only to gain his point! He will launch a curse upon the world, and as only man can curse (it is his privilege, the primary distinction between him and other animals), may be by his curse alone he will attain his object--that is, convince himself that he is a man and not a piano-key! If you say that all this, too, can be calculated and tabulated--chaos and darkness and curses, so that the mere possibility of calculating it all beforehand would stop it all, and reason would reassert itself, then man would purposely go mad in order to be rid of reason and gain his point! I believe in it, I answer for it, for the whole work of man really seems to consist in nothing but proving to himself every minute that he is a man and not a piano-key!"

Fyodor Dostoyesky, Notes from the Underground, 1864.

Deterministic versus non-deterministic: can we tell the difference?

Variation with the agents: choosing, learning, evolving

Beyond agents and environments ... multilevel architectures
Langton's Ant and Segregation/Integration both involve no more than local interactions among agents, among environmental locations, and between agents and environmental locations. They also lack any explicit representation of "purpose" in the agents. Can one add more global information to agents? Some more explicit representation of "purpose"? Are there universes within which more elaborate agents perform better than simpler ones?

Taking motivation from the brain

  • the brain functions emergently
    • neurons = interconnected agents communicating locally
    • multilevel architecture
    • generates meaningful, causally significant "purpose"
and from forms of social organization
and from emergence

Local interactions with bilevel architectures yielding more global information and greater "purpose"?

The beginnings of an exploration along these lines

How evolve from flat architectures to multilevel ones?

Consider modifications of either Langton's Ant or Segregation/Integration or further development of the explorer problem or ???? in light of the above questions and constraints. We'll next start looking more at learning, rule changes, evolution ... keep your models in mind for further elaboration as course projects? Thoughts in blog about where we are? where we still ought to be exploring?

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