Analyzing the empirical course of forgetting.

An analysis of the temporal properties of forgetting can be performed whenever memory is assessed at more than one retention interval. With regard to the singular property of forgetting rate, however, any theoretical interpretation is complicated by the possibility of a nonlinear scale relating a given performance measure (e.g., number of items recalled) to an underlying process. Because that scaling relationship is generally unknown, many conclusions about the rate of forgetting based on a performance measure cannot be assumed to reflect the memory process of interest. In an effort to deal with that problem, several methods of analysis have been proposed that generally yield opposing conclusions about whether a higher degree of learning results in a slower rate of forgetting. The present article describes four properties of empirical forgetting functions that may, at different times, be taken to represent the rate of forgetting and illustrates the potentially confusing practice of assigning the same verbal label to each. The difference between performance-based and psychological views of forgetting and the role of that distinction in determining ones approach to the analysis of empirical forgetting functions are also considered. A subject of long-standing interest in the field of learning and memory is the temporal course of forgetting. Recent studies concerned with this issue have examined the form of forgetting functions spanning as few as 15 s to as many as 50