http://www.weeklystandard.com/Content/Public/Articles/000/000/002/852lodkv.asp
This fascinating article shows pretty conclusively that at least some people are optimizers, although maybe they're the exception. BTW, if you ever need to have an A+ grade removed from your academic record, read the article because it shows you how. On a different note, I have some comments on why many people seem to be rule followers rather than optimizers. Consider evolution as an AI designer. Any AI designer faces two major problems: 1. Design a decision algorithm that improves utility, taking into account the costs of computation. 2. Prevent misinterpretation and random drift of the utility function. Problem 1 obviously implies using simpler subroutines when stakes are low, and more complex resource-intensive subroutines when stakes are high. The traditional justification for modeling people as perfect optimizers is that the model will match reality when stakes are high enough, and who cares about the low stakes situations? But if you think about problem 2, you'll realize that there may be a net advantage to following rules blindly even when the stakes are high. A perfect optimizer who behaves according to decision theory (or some bounded-rationality version of it) is very vulnerable to small changes in its utility function definition or the module responsible for interpreting the meaning of terms in the utility function definition. Such a change, say a bit flip caused by cosmic radiation, or the introduction of a new philosophical idea, could cause the agent to behave completely counter to the designer's intentions. In the rule-based agent, on the other hand, the utility function definition and its interpretation are effectively dispersed throughout the set of rules. If the rules are designed with appropriate redundancy, it should be much less likely for a catastrophic change in behavior to occur.
