DEVELOPMENTAL REVIEW 16, 284–300 (1996) ARTICLE NO. 0012 Measuring Infant Memory RICHARD S. BOGARTZ University of Massachusetts, Amherst Existing memory measures L/I, L/B, L/(L / I) and L/(L / B) are defined in terms of baseline response rate, B, response rate immediately after acquisition, I, and response rate at a long-term retention test, L. These measures are compared to a new measure S Å (L 0 B)/(I 0 B). S, the fraction of acquired kicking rate remaining at the end of the retention interval, is preferred to the existing measures. S graphically portrays the forgetting function. Point estimates and confidence intervals can be used to describe the proportion retained and to test hypotheses about the memory level. This is an improvement over the ordinal tests performed with the existing measures. ANOVAs can be performed on S values to compare retention over days and between treatment groups. S estimates provide the basic data for fitting candidate forgetting laws to the obtained data. S appears to be a virtually unbiased estimator of the true proportion retained and has sensitivity comparable to that of the best of the existing measures.  1996 Academic Press, Inc. Recent research has been devoted to the study of infant memory in the early months of life (Bhatt & Rovee-Collier, 1994; Bhatt, Rovee-Collier, & Shyi, 1994; Bhatt, Rovee-Collier, & Weiner, 1994; Butler & Rovee-Collier, 1989; Davis & Rovee-Collier, 1983; Fagen, Yengo, Rovee-Collier, & Enright, 1981; Fleckenstein & Fagen, 1994; Greco, Hayne, & Rovee-Collier, 1990; Hill, Borovsky, & Rovee-Collier, 1988; Ohr, Fleckenstein, Fagen, Klein, & Pioli, 1990; Rovee-Collier, 1990; Rovee-Collier, Adler, & Borza, 1994; Rovee-Collier, Borza, Adler, & Boller, 1993; Rovee-Collier & Dufault, 1991; Rovee-Collier & Hayne, 1987; Rovee-Collier & Shyi, 1992; Rovee-Collier, Sullivan, Enright, Lucas, & Fagen, 1980; Shields & Rovee-Collier, 1992; Sullivan, 1982). Using an operant conditioning paradigm, the basic approach has been to measure the base rate of a kicking response, condition the kicking response by making motion of a mobile contingent upon kicking as a result of a direct connection from the infant’s foot to the mobile, and then study I am indebted to two anonymous reviewers for suggestions concerning the content of the section on Broader Considerations. Address correspondence and reprint requests to Richard S. Bogartz, Department of Psychology, University of Massachusetts, Amherst, MA 01003. E-mail: Bogartz@Wilde.Umass.edu. 0273-2297/96 $18.00 Copyright  1996 by Academic Press, Inc. All rights of reproduction in any form reserved. 284