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Description: Presenting items multiple times on a study list increases the probability that they will be recalled or recognized on a subsequent memory test—a process known as item strengthening. The list-strength effect (LSE) refers to the finding that, compared to unstrengthened (pure) lists, lists for which a subset of the items have been strengthened produce enhanced memory for the strong items and depressed memory for the weak items. In other words, the strong-item advantage is larger in mixed lists than pure lists. Although the LSE is found in free recall (Tulving & Hastie, 1972), it does not occur in recognition (Ratcliff, Clark, & Shiffrin, 1990). Interestingly, the free-recall and recognition literatures on the LSE have largely developed independently, such that proposed explanations in free recall have not been tested in recognition and vice versa. In free recall, the LSE is attributed to a sampling bias for strong items in mixed lists and consequent output interference of mixed-weak items. We suggest that the disruption of this pattern through randomized test probes in recognition is responsible for the null LSE. We present several pilot experiments consistent with this account, and propose a registered study that will provide a clearer test.