Paul Grobstein, Bryn Mawr College Department of Biology
Clare Congdon, Bryn Mawr College Computer Science Program

Lab 2: Linear versus non-linear interactions

Your explorations during the first week should have persuaded you that this statement is indeed true, and hence that order can emerge from not only the actions of a designer and from an evolutionary process but also an "emergent property" of "self-organizing systems". How these various possible causes of order relate to one another is a question that has occurred to several of you, and one that we might want to keep in mind as the course proceeds. For the present, we want to begin looking in more detail at what accounts for the appearance of "interesting" behavior in self-organizing systems. One relevant feature is that the interactions among elements are generally "non-linear". This property not only (sometimes) leads to interesting behavior, but is also the reason why such systems were not readily explorable prior to the ready availability of fast computers.

Our objective for this week is to develop some intuitions about the significance of the distinction between "linear" and "non-linear" interactions by looking at a "simplified" complex system, one in which there are only two interacting elements and we can compare the behavior when the elements interact linearly and non-linearly. Serendip's On Beyond Newton provides a discussion and interactive illustration of some of the kinds of interesting behaviors that can emerge from non-linear interactions. A modified version of the Java applet in On Beyond Newton allows one to compare behaviors in the case of linear and several kinds of non-linear interactions.

You should work through these materials, following additional available links (or other materials) as you find them interesting and write in your journal about both the understandings that emerge for you and new questions that arise in your mind. During this week you should also continue developing your own ability to create models of complex systems, by becoming more proficient in either Java programming or StarLogo programming. Resources, including on-line tutorials for the latter are available through the StarLogo Home Page, and the Maine StarLOGO Communities.

A more specific computer-skills assignment:

1. Set yourself a goal for this week that is compatible with your current background in Unix and/or programming. For example:
   • If you are new to Unix, your goal might be simply to learn to use MacX and textedit. For example, learn to do your journal entry entirely on the Unix side.
   • If you've used Unix a bit before, your goal might be to start learning the Emacs editor. Again, maybe the goal is to learn to write your journal entries in Emacs. (Note that you can use emacs via telnet, so you can do this remotely.)
   • If you're familiar with Unix and programming (and are taking this class for CS credit), your goal should be to complete the first several sections of The Java Tutorial. (Stick to the "applets", not the "applications")
   • If you've done Java programming before (I don't think any of us have done applets before), your goal should be to look at the source code for On Beyond Newton or the Game of Life, and learn from it.

2. Seek Clare or Paul's help in defining and pursuing your goal.

3. Pursue your goal and report questions and accomplishments in your journal.