The role of background knowledge in speeded perceptual categorization

We examined the time-course of the influence of background knowledge on per ceptual categorization by manipulating the meaningfulness of labels associa ted with categories and by manipulating the amount of time provided to subj ects for making a categorization decision. Extending a paradigm originally reported by Wisniewski and Medin (1994) (Cog, Sci. 18 (1994) 221), subjects learned two categories of children's drawings that were given either meani ngless labels (drawings by children from 'group 1' or 'group 2') or meaning ful labels (drawings by 'creative' or 'non-creative' children); the meaning fulness of the label had a significant effect on how new drawings were clas sified. In addition, half of the subjects were provided unlimited time to r espond, while the other half of the subjects were forced to respond quickly ; speeded response conditions had a relatively large effect on categorizati on decisions by subjects given the meaningless labels but had relatively li ttle effect on categorization decisions by subjects given the meaningful la bels. These results suggest that some forms of background knowledge can sho w an influence at relatively early stages in the time-course of a categoriz ation decision. (C) 2000 Elsevier Science B.V. All rights reserved.