Full context:   Political and socioeconomic revolutions have been studied in many social sciences, particularly sociology, political science and history. Scholars of revolution differentiate four generations of theoretical research on the subject of revolution. Theorists of the first generation, including Gustave Le Bon, Charles A. Ellwood, and Pitirim Sorokin, were mainly descriptive in their approach, and their explanations of the phenomena of revolutions were usually related to social psychology, such as Le Bon's crowd psychology theory. The second generation sought to develop detailed frameworks, grounded in social behavior theory, to explain why and when revolutions arise. Their work can be divided into three categories: psychological, sociological and political.