This article was presented at the May 1995 meeting of the Midwestern Psychological Association in Chicago. Work on this article was supported in part by a National Science Foundation fellowship to G. Scott Acton.
Correspondence concerning this article should be addressed to G. Scott Acton, Department of Psychology, Northwestern University, 2029 Sheridan Rd., Evanston, Illinois 60208-2710. Electronic mail may be sent to acton@northwestern.edu.