On the reliability of implicit and explicit memory measures

Functional dissociations between implicit and explicit memory tests often take the form of large differences between groups or experimental conditions (e.g., amnesics and controls, elderly and younger persons, or persons learning with and without a distracting secondary task) when performance is assessed using explicit memory tests, whereas no difference is observed with implicit memory tests. We argue that the interpretation of such dissociations in terms of the memory processes or systems involved in performance is problematic because the same data pattern would emerge as a result of a mere methodological artifact, that is, the situation that implicit memory tests have low reliability whereas explicit memory tests are fairly reliable measurement instruments. We present reasons for such a reliability difference, and we demonstrate it empirically in Experiments 1a, 1b, and 2. However, our analysis also shows, and Experiment 3 confirms empirically, that implicit memory tests need not necessarily be less reliable measurement instruments than explicit memory tests.