The author's stated purpose is to convince the reader that there is practical and theoretical importance in a general principle whereby the greater the amount of interference present during the initial learning of a particular task, the better the subsequent retention to new situations. The author attempts to convince the reader with empirical data showing that interference during learning facilitates subsequent retention or transfer, and also attempts to describe this relationship in a way that makes good intuitive sense. On the basis of the empirical evidence presented, it is concluded that these psychological experiments on the effects of intratask interference during original learning on subsequent retention or transfer, leaves no alternative but to take seriously the facilitative nature of these effects. The need is also expressed for research conducted in educational and applied-learning settings, rather than the psychological laboratory, to determine whether the principle can in fact be generalized to nonlaboratory situations. (BW/Author)