Norm Theory : Comparing Reality to Its Alternatives

probe such as a category name, and that a norm is This work was supported by the Office of Naval Research under Grant NR 197-058, and by grants from the National Science and Engineering Research Council of Canada and from the Social Sciences and Humanities Research Council of Canada (410-68-0583). Dale Griffin, Leslie McPherson, and Daniel Read provided valuable assistance. Many friends and colleagues commented helpfully on earlier versions. The comments of Anne Treisman and Amos Tversky were especially influential. The preparation of the manuscript benefited greatly from a workshop entitled "The Priority of the Specific," organized by Lee Brooks and Larry Jacoby at Elora, Ontario, in June of 1983. Correspondence concerning this article should be addressed to Daniel Kahneman, who is now at the Department of Psychology, University of California, Berkeley, California 94720, or Dale Miller, Department of Psychology, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada. produced by aggregating the set of recruited representations. The assumptions of distributed activation and rapid aggregation are not unique to this treatment. Related ideas have been advanced in theories of adaptation level (Helson, 1964; Restle, 1978a, 1978b) and other theories of context effects in judgment (N. H. Anderson, 1981; Birnbaum, 1982; Parducci, 1965, 1974); in connectionist models of distributed processing (Hinton & Anderson, 1981; McClelland, 1985; McClelland & Rumelhart, 1985); and in holographic models of memory (Eich, 1982; Metcalfe Eich, 1985; Murdock, 1982). The present analysis relates most closely to exemplar models of concepts (Brooks, 1978, in press; Hintzman, in press; Hintzman & Ludlam, 1980; Jacoby & Brooks, 1984; Medin & Schaffer, 1978; Smith & Medin, 1981). We were drawn to exemplar models in large part because they provide the only satisfactory account of the norms evoked by questions about arbitrary categories, such as "Is this person friendlier than most other people on your block?" Exemplar models assume that several representations are evoked at once and that activation varies in degree. They do not require the representations of exemplars to be accessible to conscious and explicit retrieval, and they allow representations to be fragmentary. The present model of norms adopts all of these assumptions. In addition, we propose that events are sometimes compared to counterfactual alternatives that are constructed ad hoc rather than retrieved from past experience. These ideas extend previous work on the availability and simulation heuristics (Kahneman & Tversky, 1982; Tversky & Kahneman, 1973). A constructive process must be invoked to explain some cases of surprise. Thus, an observer who knows Marty's affection for his aunt and his propensity for emotional displays may be surprised if Marty does not cry at her funeral—even if Marty rarely cries and if no one else cries at that funeral. Surprise is produced in such cases by the contrast between a stimulus and a counterfactual alternative that is constructed, not retrieved. Constructed elements also play a crucial role in counterfactual emotions such as frustration or regret, in which reality is compared to an imagined view of what might have been (Kahneman & Tversky, 1982). At the core of the present analysis are the rules and constraints that govern the spontaneous retrieval or construction of alter-