When some items on a list are strengthened by extra study time or repetitions, recognition of other, unrelated, list items is not harrned (Ratcliff, Clark, & Shiffrin, 1990). Shiffrin, Ratcliff, and Clark (1990) accounted for this list-strength finding with a model assuming that different items are stored separately in memory, but that repetitions are accumulated together into a single stronger memory trace. Repeating words in the contest of different sentences might cause separate storage of the repetitions of a given word, because either word or sentence traces are stored separately. ¶te storage would, in effect, convert a list-strength manipulation into a list-length manipulation and thereby induce a positive list-strength effect. In Experiment 1, this result was produced for single-word recognition ant for two types of sentence recognition. In Experiment 2, both words and sentences were repeated together, which should have caused repetitions to be stored in a single, stronger, trace. As expected, the list-strength effect was eliminated. A sentence trace model was fit to the data, supporting the account of Shiffrin et al. ( 1990) and supporting an account of word and sentence recognition in which activation is summed for representations of all list items. The results from the two studies are inconsistent with most cur- rent models of memory (as shown by the theoretical analyses of Shiffrin et al., 1990) and pose an additional challenge for theory.