Integrating Decay and Interference: A New Look at an Old Interaction

An old but important debate about human memory concerns whether decay (indexed by time) or interference (indexed by amount of distracting information) is the cause of forgetting. We argue, based on a simple functional analysis, that this is a false dichotomy. Both processes must be at work, in that distracting information must decay to allow the cognitive system to have any hope of retrieving target information amidst the unavoidable clutter of a well-stocked memory. This analysis predicts that subtle decay effects should be pervasive, even in data produced by interference theorists to show that decay was impossible. A re-analysis of data from Waugh and Norman (1965) does indeed reveal decay effects that were dismissed by the authors as inconsequential and have been ignored by most investigators since. We fit a formal model integrating decay and interference to the Waugh and Norman data, and to the decay data of Peterson and Peterson (1959) to show that one model provides an improved account of two ostensibly divergent data sets