The Von Restorff Effect in Free Recall, Recognition, and Source Memory

Distinct items encountered in a sequence are better recalled than the less distinctive items (Von Restorff, 1933). This is often referred to as a von Restorff or an isolation effect. There is rarely an isolation effect for recognition, which is inconsistent with intuition and all known theories of memory. Three experiments extend prior findings to a multilist procedure, confirming a free recall advantage for unexpected words, but no recognition advantage unless recall is tested before recognition. A somewhat ambiguous effect was observed when source memory was tested. Based on these results, we hypothesized that the lack of a von Restorff effect for recognition is due to constraints on traditional designs used to study isolation effects and perhaps uncontrolled factors during testing. In three additional experiments targeted specifically at observing isolation effects in recognition and source memory, we obtained more observations per subject in the critical condition, reducing measurement error, and controlled the order in which items in recognition and source memory were tested. The results revealed von Restorff effects for both recognition and source memory. Implications for models of memory are discussed.