An experiment which would disprove my hypothesis regarding more bidding increments would be something like:

Run at least three auctions for the same or similar items with the same or similar bidders, one using normal estimates and bidding increments for a control, one where the low estimate was lowered to allow more increments, and one with the same estimates, but more granular increments. IF the price paid in each auction was roughly equivalent, THEN the hypothesis is disproven.

The problem with that is the nature of the property we auction -- there's only one of anything. Each auction lot is, in important ways, different from the others. There's only one of this painting; only one of this desk. Even when two objects are similar, there are still often condition differences and so forth.

I'll have to consult with some of the appraisers and see if there's ever an exception to this rule.

But ok, that brings up another interesting question. Is there a way of simulating auction behavior? Has someone written a computer program to do this sort of thing? What kinds of assumptions do they make about the behaviors of individual agents?