The production effect in recognition memory: Weakening strength can strengthen distinctiveness.

Producing items (e.g., by saying them aloud or typing them) can improve recognition memory. To evaluate whether production increases item distinctiveness and/or memory strength we compared this effect as a function of the percentage of items that participants typed at encoding (i.e., 0%, 20%, 50%, 80%, and 100%). Experiment 1 revealed a strength-based pattern: The production effect was similar across pure-list (i.e., 0% vs. 100%) and mixed-list (i.e., 20%, 50%, 80%) designs, and there was no observed influence of statistical distinctiveness (i.e., 20% vs. 80%). In Experiment 2, we increased the study time for unproduced items to minimise the strength difference between produced and unproduced items. The manipulation attenuated the pure-list effect without eliminating the mixed-list effect, providing support for the inference that the mixed-list effect reflects distinctiveness. An influence of statistical distinctiveness also emerged: The mixed-list effect was larger when participants produced only 20%, rather than 80%, of the items. These findings suggest that both strength and distinctiveness contribute to the production effect in recognition.