The list-strength effect in recall: relative-strength competition and retrieval inhibition may both contribute to forgetting.

According to the principle of relative-strength competition, stronger items in memory block the retrieval of weaker items. This principle, integral to many theories of forgetting over the years, derives much of its support from the list-strength effect (LSE), in which strengthening some items in a study list makes it more difficult to recall other items. Work in the retrieval-induced forgetting literature has challenged the existence of relative-strength competition, 1st by offering many examples of a null LSE and 2nd by proposing that extant observations of the LSE can be explained by retrieval inhibition. In the present study, a series of experiments produced a robust LSE in cued recall under conditions meant to control the contribution of retrieval inhibition. Simulations of the SAM-REM model of recall (K. J. Malmberg & R. M. Shiffrin, 2005) showed that a model based on relative-strength competition can accommodate both the presence and absence of an LSE. The empirical results and model simulations together make a case for the role of strength-based competition in forgetting.