Context eects in political judgement: assimilation and contrast as a function of categorization processes HERBERT BLESS 1 * and NORBERT SCHWARZ 2 1 Psychologisches Institut, University of Trier, Germany 2 University of Michigan, U.S.A. Abstract Two experiments demonstrate that thinking about a given politician may result in assimilation as well as contrast eects in evolutions of the politician's party. In two experiments, assimilation eects were observed when an experimental categorization task elicited the inclusion of a highly respected politician in the representation formed of his party, whereas contrast eects were observed when the categorization task elicited his exclusion from the representation, with the control group falling in between. Hence, the same information may elicit assimilation as well as contrast eects, depending on its use in mental construal. # 1998 John Wiley & Sons, Ltd. INTRODUCTION The notion that social judgments are context dependent has a long tradition from ancient philosophical treatments of human reasoning to current theorizing in social cognition (see Eiser, 1990; Tartarkiewicz, 1984). Here, we focus on a particular instantiation of context eects, namely the impact of a given politician on evaluations of his or her party. There is wide agreement among researchers that assimilation and contrast eects may re¯ect the operation of a number of dierent processes, which have been conceptualized in independent, and apparently unrelated, theories (see Eiser [1990] for a review). One group of theories focused on the distribution of the contextual stimuli, assuming that they in¯uence the adaptation level (Helson, 1964), standard of comparison (e.g. Thibaut & Kelley, 1959), or scale anchor (e.g. Ostrom & CCC 0046±2772/98/020159±14$17.50 Received 10 September 1996 # 1998 John Wiley & Sons, Ltd. Accepted 2 January 1997 European Journal of Social Psychology Eur. J. Soc. Psychol. 28, 159±172 (1998) * Address for correspondence: Herbert Bless, FB-I Psychologie, UniversitaÈ t Trier, D-54286 Trier, Germany. The reported research was supported by grant Bl 289/5-1 from the Deutsche Forschungsgemeinschaft to H. Bless, N. Schwarz and M. WaÈnke.