People asked to categorize exemplars of 2 categories often respond more accurately to the prototypes of those categories than to other exemplars. The authors suggest that this prototype effect may often have been confounded with apeak shift as is observed when pigeons are trained to discriminate between two wavelengths (S+ = 550 nm and S-= 560 nm), and the peak of their postdiscrimination gradient lies at 540 or 530 nm rather than at 550 nm. Three experiments established that a similar peak shift can occur when people are asked to categorize 2 sets of stimuli. but the authors also provide evidence of a true prototype effect uncontaminated by any peak shift. These results appear to pose considerable problems for exemplar-based theories of categorization.If people are required to classify two sets of stimuli, patterns, shapes, letter strings, and so forth into two different categories in which each set can be described as a series of variants on two prototypes, they will often, on test, classify the two unseen prototypes significantly more accurately than new exemplars of either category (e.g., Posner & Keele, 1968); also there are instances of better performance on the prototypes or stimuli close to them than on the actual stimuli on which participants were trained (e.g.,
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.