Joe,

Peter M. Todd and Bernhard Borges followed on the idea with a paper
called "Designing Socially Intelligent Agents For The Ultimatum Game."
The paper can be found here:
http://www.mpib-berlin.mpg.de/DOK/full/tod...soci/tpdessoci.html
(I especially recommend reading the first paper. They run a more
sophisticated model with many more variants of limited reasoning
abilities for the agent.)

They seem to have presented more work related to this, but I can't find
where it was published. Try:
http://bucky.stanford.edu/cef97/abstracts/borges2.html
(It is interesting what they say in the abstract: "In particular, our results
suggest that evolution will find and use only those reasoning abilities
that aid RL.") If anybody finds the paper, please tell me!

Hector