The NetLogo model discussed in my paper Modalizing Mechanisms.
Put modalizing-mechanisms.nlogo and utils.nls in the same directory and
open modalizing-mechanisms.nlogo with
NetLogo. Any 5.x version should work.
Please refer to the info tab of the model and to the related paper for explanation of what it attempts to show.
I'll try to keep an up-to-date copy of this model over at Modeling Commons.