 Norbert Schwarz's work on categorization and mental construal led to the development of his inclusion/exclusion model that accounts for the emergence of contrast and Assimilation effects in social judgments.Contrast effects occur when exposure to valenced information influences judgments in a way that is incongruent with the valenced information.Assimilation effects occur when exposure to valenced information influences judgments in a way that is congruent with the valenced information.