Forgetting functions

Forgetting functions describe how accuracy or discriminability declines as the temporal distance from the event to be remembered increases. Several two-parameter mathematical functions are equally successful in fitting data from a range of studies. The choice of function must therefore be made on theoretical grounds. Consistent with the proposal that remembering follows the principles of discrimination, remembering is specific to the time of retrieval and is independent of the level of performance at earlier times in the retention interval. Empirical evidence for this temporal independence supports constant-rate forgetting. Exponential functions are therefore favored descriptions of forgetting functions because they describe how the influence of the temporally distant event declines at a constant rate. A combination of exponential generalization with an exponential decrease in the effect of the temporally distant stimulus holds promise as a theoretical account of forgetting functions.