A preference for negative reciprocity is an important part of the human emotional repertoire. We model its role in sustaining cooperative behavior but highlight an intrinsic free-rider problem: the fitness benefits of negative reciprocity are dispersed throughout the entire group, but the...

We discuss how small group interactions overcome evolutionary problems that might otherwise erode vengefulness as a preference trait. The basic viability problem is that the fitness benefits of vengeance often do not cover its personal cost. Even when a sufficiently high level of vengefulness...

This paper analyzes seller characteristics and choices in approximately 1000 eBay auctions for a particular model of PDA. Seller characteristics include frequency of selling, reputation, and the qualities of the product sold. Seller choices include the length of the auction, information provided...

This paper analyzes seller choices and outcomes in approximately 700 recent Internet auctions on eBay. The 'Buy it Now' option that is available in these auctions allows the seller to supplement or replace the auction with a posted price offer. We use a structural model to control for the...

Human players in our laboratory experiment received flow payoffs over 120 seconds each period from a standard Hawk-Dove bimatrix game played in continuous time. Play converged closely to the symmetric mixed Nash equilibrium under a one-population matching protocol. When the same players were...

A complete set of transactions, more than 40 million within a 1.8 year span, allows us to track the evolution of the trader network and the goods network in an on-line trading community. The computer platform was designed to make barter exchange as attractive as possible; money was not part of...

Prior laboratory experiments have studied general equilibrium economies constructed from “induced preferences” for artificial goods. We introduce new methods that allow us to study economies constructed instead from subjects' actual, “homegrown" preferences. Our subjects reveal their...

We explore a variety of risk preference elicitation procedures that involve direct choice from a set of lotteries, including budget lines (BL) and binary choice lists (HL). We find statistically significant violations of the expected utility hypothesis (EUH) consistent with disappointment...

We report agent-based simulations of religiosity dynamics in a spatially dispersed population. Agents' religiosity responds to neighbors via pairwise interactions as well as via club goods effects. A simulation run is deemed fundamentalist if the final distribution contains a sizable minority of...

Investors' Exchange LLC (IEX) is a newly approved public exchange that is designed to discourage aggressive high-frequency trading. We explain how IEX differs from traditional continuous double auction markets and present summary data on IEX transactions by trader class and or- der type. Our...