This book describes a quantitative model that can reproduce with great accuracy the results of a number of important studies in the area of memory, including the pioneering experiments published by Ebbinghaus in 1885. The results of a variety of published studies involving the learning of a list of items (or the recall of an individual item) can be explained by discovering how the forgetting of each individual item can be reproduced using only a knowledge of the item’s serial position in a list and the length of the list to which it belongs (even if the list contains only one item), and the duration(s) of any study period(s) and any forgetting period(s) involved. When a list is being learned, the middle items of the list are learned more slowly than those at the beginning or the end, and the list can only be considered fully mastered when the slowest item to be learned can be recalled correctly. The crucial determinant of recall at any point during the learning of a list is the rate of forgetting of each item during each forgetting period. The model includes a component that may be identified with the ‘phonological buffer’ in the working memory model (Baddeley & Hitch,1974) and is similar to the concept of ‘primary memory’ proposed by William James (1907), but not the concept of ‘short-term memory’ as it appears in the ‘modal model’ of Atkinson and Shiffrin (1968). Rather, the evidence shows that forgetting is initially postponed for a short period before recall subsequently begins to decline exponentially against time in a way that requires no distinction between short and long term delays. In the case of each item the size of the forgetting exponent decreases during the first study period and decreases progressively more during successive study periods. The forgetting exponent increases somewhat during any delay before recall, but this increase is reduced by repeated study periods. The magnitude of these effects can be calculated from the available data. When approached in this way, very accurate predictions can be made of the recall of an individual item after any specified delay, and also of the number of readings it will take to learn a list. There is no need to invoke hypothetical ‘stores’ or mechanisms to account for the retention of material, and no need to distinguish between short-term and long-term memory: there is simply a continuum of forgetting. The concept of a ‘short-term store,’ with a limited capacity, such as the ‘magic number 7±2’ (Miller, 1956), and a duration of about 15-18 seconds, that has often been inferred from studies such as that of Peterson and Peterson (1959), is revealed as specious. Such a concept has a simplicity and an apparent ability to explain a narrow range of phenomena, but an in-depth analysis of the available data reveals that those features only emerge in specific circumstances that can be explained within a more comprehensive theory of memory.