A brief statement of the community of function between certain learning situations, as applied to rats in the Stanford psychology laboratory, is given in a recent paper by Commins, McNemar, and Stone (2). One of the chief contributions of that paper is the fact that a multiple-T alley maze and two diverse patterns of the Miles types of elevated maze (13) repeatedly yielded intercorrelations of approximately .6, whereas each of these instruments yielded only zero coefficients when correlated with a multiple light discrimination apparatus ( 19). The latter fact, confirming in part some unpublished data collected by Stone and Nyswander in 1927, in connection with their study of maze reliability (18), and likewise somewhat similar findings independently obtained by Williams (28), would seem to be a discovery of capital importance for students of individual differences in animals because it clearly establishes the fact that two fairly reliable instruments may have no community of function.We look upon this discovery as one of capital importance because now-a-days many problems in animal psychology are attacked by laboratorymethods masquerading under the same name, but differing from each other in many essential details. So long as this continues to be the case, and so long as we lack accurate information as to the community of function of these diverse techniques of experimentation, just so long shall we continue to grope in the dark while seeking plausible explanations of the divergent results obtained on fundamental problems. Naturally, with the mere demonstration of community of function or absence of the same in different experimental settings we should not stop experimentation, for this demonstration is merely a first step 73