The study of collective behavior spun its wheels for many years, but began to make progress with the appearance of Turner and Killian's "Collective Behavior" (1957) and Smelser's "Theory of Collective Behavior" (1962). Both books pushed the topic of collective behavior back into the consciousness of American sociologists and both theories contributed immensely to our understanding of collective behavior (; ). Social disturbances in the U. S. and elsewhere in the late '60s and early '70s inspired another surge of interest in crowds and social movements. These studies presented a number of challenges to the armchair sociology of earlier students of collective behavior.