SIMILARITY IN CONTEXT

Similarity comparisons are highly sensitive to judgment context. Three experiments explore context effects that occur within a single compar ison rather than across several trials. Experiment 1 shows reliable in transitivities in which a target is judged to be more similar to stimu lus A than to stimulus B, more similar to B than to stimulus C, and mo re similar to C than to A. Experiment 2 explores the locus of Tversky' s (1977) diagnosticity effect in which the relative similarity of two alternatives to a target is influenced by a third alternative. Experim ent 3 demonstrates a new violation of choice independence which is exp lained by object dimensions' becoming foregrounded or backgrounded, de pending upon the set of displayed objects. The observed violations of common assumptions to many models of similarity and choice can be acco mmodated in terms of a dynamic property-weighting process based on the variability and diagnosticity of dimensions.