British Journal of Social Psychology (2019), 58, 105–128 © 2018 The British Psychological Society www.wileyonlinelibrary.com Special section paper Nonlinear societal change: The perspective of dynamical systems Andrzej Nowak 1,2 and Robin R. Vallacher 2 * 1 Department of Psychology, University of Warsaw, Poland 2 Florida Atlantic University, Boca Raton, Florida, USA Although rapid social change reflects each society’s unique combination of myriad social, historical, political, and economic factors, we argue that the defining features of such change can be understood with recourse to the dynamic processes inherent in complex systems. Accordingly, we present a formal model that describes, in minimalist terms, the dynamics associated with rapid societal transitions in a society’s norms and attitudes— and to the potential for rapid reversals of these transitions. The model predicts that societies in the midst of rapid change are characterized by dual realities corresponding to the new and the old, so that models focusing only on changes in the central tendency of a societal attitude provide a misleading account of rapid social change. This model is implemented in computer simulations and validated with empirical data concerning the transition in Eastern Europe from communism to democracy and a free market economy in the late 1980s. Background Societies around the world are undergoing significant changes that are rapid, complex, and often unanticipated. Norms, beliefs, and attitudes that have withstood the test of time and seemingly were permanent fixtures within a culture have been challenged and undergone substantial revision in often astonishing short periods of time. This is readily apparent with respect to economic and political change. The Soviet-dominated regimes that held sway in Eastern Europe for several decades after World War II, for example, gave way to democratic and capitalist reforms in a matter of months in the late 1980s. Recent years, meanwhile, have witnessed the rapid rise of radicalization and terrorism emanating in parts of the Middle East, the sudden ascendance of nationalism and populism in stable European countries, and the overnight emergence of the Arab Spring followed in short order by the Arab Winter. Rapid changes have also occurred with respect to social values. Attitudes towards homosexual relations which had persisted unchanged for decades, for example, have shifted substantially in recent years: the percentage of Americans who support gay marriage almost doubled from 1997 (35%) to 2017 (64%) (Gallup poll, 3–7 May 2017). A similarly dramatic shift in opinion has occurred regarding acceptance of inter-racial marriage—a mere 4% approved of marriage between white and black *Correspondence should be addressed to Robin R. Vallacher, Department of Psychology, Florida Atlantic University, 777 Glades Road, Boca Raton, Florida 33433, USA (email: vallacher@gmail.com). DOI:10.1111/bjso.12271 105