Int. J. Human-Computer Studies (1999) 50, 000-000 Article No. ijhc.1998.0255 Available online at http://www.idealibrary.com on IDEL Simulating arcs and rings in gatherings CHARLES W. TUCKER Department of Sociology, University of South Carolina, Columbia, SC, USA. email: cwtucker@sc.edu DAVID SCHWEINGRUBER AND CLARK MCPHAIL Department of Sociology, University of Illinois-Champaign, Urbana, IL, USA. email: cmmcphail@uiuc.edu;dschwein@uiuc.edu A theory of collective behavior must be able to account for simple and common collective phenomena such as arcs and rings. Using a computer simulator designed according to the principles of Perceptual Control Theory, based on a model how a human being. as a living control system, engages in movement alone and with others in temporary gatherings we produced a highly symmetrical ring that remotely corresponds to the non-simulated world because it is made up exclusively of individua1s. When we simulated the pairs that compared to non-simulated gatherings, the outcome was an arc but was still unlike those we have observed in many temporary gatherings. When we introduced disturbances into the gatherings in the form of other simulated actors they more closely represented what we have observed in the non-simulated world of parks, plazas, states fairs and school yards as well as those at political, religious and rallies. We offer several proposals for future research. .. ,. @ 1999 Academic Press 1. Introduction In public places like London's Hyde Park or New York City's Washington Square, it is common to see persons arrayed in arcs or rings around entertainers, political and religious speakers, or other points of common focus. Of these arrangements, Milgram and Toch write (1969, p. 518): If individuals are randomly distributed over a fiat surface in the starting situation, a point of common interest in the same plane creates a crowd tending toward circularity. The circular arrangement is not accidental but seems an important function. It permits the most efficient arrangement of individuals around a point of common focus. A theory of collective behavior must be able to account for simple and common collective phenomena such as arcs and rings. Elsewhere we have examined arcs, rings and clusters, Collective locomotion and other simple forms using field observation (McPhail, 1991, 1994b; McPhail & Wohlstein, 1986), experiments (McPhail & Wohlstein, 1986) and computer simulations (McPhail, Powers & Tucker, 1992; Schweingruber, 1993). We have argued that Perceptual Control Theory (PCT) (powers, 1973, 1989) is the best existing theory for accounting for purposive individual behavior and have proposed an explanation for collective behavior based on this theory (McPhail & Tucker, 1990; McPhail, @ 1999 Academic Press 1071-5819/99/00000o + 08 $30.00/0