What some concepts might not be.

A discussion of the difficulties of prototype theories for describing compositional meaning motivates three experiments that inquire how well-defined concepts fare under paradigms that are commonly interpreted to support the prototype view. The stimulus materials include exemplars of prototype categories (sport, vehicle, fruit, vegetable) previously studied by others, and also exemplars of supposedly well-defined categories (odd number, even number, female, and plane geometry figure) Experiment I, using these materials, replicated the exemplar rating experiment of Rosch (1973). It showed that both the well-defined and prototypic categories yield graded responses, the supposed hall-mark of a family resemblance structure. Experiment II, using the same sorts of stimulus materials, replicated a verificationtime paradigm, also from Rosch (1973). Again, the finding was that both welldefined and prototypic categories yielded results previously interpreted to support a family-resemblance description of those categories, with faster verification times for prototypical exemplars of each category In Experiment *We are indebted to quite a large number of colleagues for discussion of the issues addressed in this paper, and for reading and commenting on prior drafts of this manuscript. Particularly, we wish to thank B. Armstrong, D. Bolinger, J. A. Fodor, J. D. Fodor, R. Gallistel, F. W. Irwin, R. Jackendoff, J. Jonides, J. Katz, L. Komatsu, B. Landau, J. Levin, J. Moravschik, E. Newport, S. Peters, M. Posner, M. Seligman, E. Shipley, E. Spelke, E. Wanner, K. Wexler, M. Williams, and an anonymous reviewer. All of us, but especially Lila Gleitman, particularly thank Scott Weinstein for his long and patient attempts to explicate the issues in philosophical semantics for us; this service, as well as reading drafts of the current paper, he has heroically extended over two years; nevertheless, he is not accountable for the manner of review of these, nor for the positions we take here, quite obviously. The work reported was funded in part by a National Institutes of Health postdoctoral Fellowship to S. L. Armstrong, and by a grant to L. R. Gleitman and B. Landau from the National Foundation of the March of Dimes. We thank these agencies for their support of this work. Felice Bedford, Manuel Ayala, and Jordan Klemes arc thanked for helping us collect the data for these studies. Reprint requests should be sent to: Lila R. Gleitman, Department of Psychology, University of Pennsylvania, 3815 Walnut Street, Philadelphia, Penna., 19104, U.S.A. 0010-0277/83/514.30 © Elsevier Sequoia/Printed in The Netherlands 264 S. L. Armstrong, L. R. Gleitman and H. Gleitman III, new subjects were asked outright whether membership in the category of fruit, odd number, etc., is a matter of degree, or is not, and then these subjects were rerun in the Experiment I paradigm. Though subjects judged odd number, etc., to be well-defined, they provided graded responses to all categories once again. These findings highlight interpretive difficulties for the experimental literature on this topic. Part I of the discussion first outlines a dual theory of concepts and their identification procedures that seems to organize these outcomes. But Part II of the discussion argues that feature theories are too impoverished to describe mental categories in general.