COMPUTATIONAL SOCIAL SCIENCE – Order without Optimality – Axtell
COMPUTATIONAL SOCIAL SCIENCE FRIDAY SEMINAR
Professor Robert Axtell
Computational Social Science Program, Department of Computational and Data Sciences, College of Science
Department of Economics, College of Humanities and Social Sciences
Center for Social Complexity
George Mason University
Order without Optimality
Friday, February 2, 3:00 p.m.
Center for Social Complexity Suite
3rd Floor, Research Hall
ABSTRACT: Long ago Hunter Mill Road in Reston, Virginia, was surrounded by farmland and little travelled. Where it crosses Colvin Run creek a single-lane bridge was adequate for the traffic at the time. However, as the region grew in the post-WWII era the traffic on Hunter Mill Road increased until the single-lane bridge is today a bottleneck for rush-hour traffic, southbound toward the Dulles Toll Road in the morning and northbound in the evening. There are no stop signs on either side of the bridge but warning signs that the bridge is too narrow to handle two vehicles moving in opposite directions at the same time. During periods of low traffic—queue length 0 or 1—the usual first-come-first-served (FCFS) driver discipline is observed at the bridge, by which the first vehicle to approach from either side has the right-of-way. However, during periods of heavy traffic, such as the morning and evening ‘rush hours’, a different behavioral regime is observed: pairs of cars moving in the same direction cross the bridge together, in single file. This departure from the FCFS protocol clearly permits higher vehicular flowrates over the bridge in each direction. However, from the layout of the bridge and vehicular dynamic we demonstrate that the globally optimal behavior for the system during busy times would involve larger numbers of vehicles moving together across the bridge, i.e., groups of 3, 4, or even 5 produce shorter wait times overall, dominating the 2-car norm. We argue that this is an example of a sub- optimal spontaneous order, and go on to suggest that there is little reason to believe that (m)any spontaneous orders operate at anything like peak performance. Essentially, spontaneous orders in this context represent behavioral norms for multi-agent coordination problems that improve on so-called anarchic solutions identified with Nash equilibria of the underlying non-cooperative game. The welfare improvements associated with following the emergent social conventions represent a kind of satisficing solution of the type identified by Herbert Simon as a good description of human behavior in a wide variety of social situations, bounded by cognitive constraints, limited information, and incentive problems. We conclude by arguing that F.A. Hayek implicitly associated his conception of spontaneous order with high welfare, but that this view is untenable. Rather, the more general idea of emergence, which makes no welfare assertions, seems to subsume spontaneous order as a very special case, suggesting that Hayek’s contribution to this area has been largely supplanted by more recent developments in the science of complex systems, as has been argued elsewhere.