Although Bogartz (1996) has engaged in an interesting mathematical exercise, he has revealed no new solution to the real-world problem of when a prior infant experience is likely to affect future behavior and has offered no behavioral evidence that his proposed measure yields outcomes substantially different from those obtained with extant measures. Moreover, his proposed measure of retention fails to recognize that response rate is not a parameter of response strength (Collier & Rovee-Collier, 1983). Our measures have concurrent validity: They yield results highly similar to those reported by infant researchers who use vastly different measures and functional relations highly similar to those reported in studies with animals and human adults. In addition, we have published evidence of their predictive validity. To quote an ancient Socratic scholar (Yogi Berra), ''If it ain't broke, don't fix it.'' (C) 1996 Academic Press, Inc.