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Perhaps the most basic finding in memory research is the repetition effect--the fact that repetition enhances memory. Peterson and Mulligan (2012) recently documented a surprising "negative repetition effect," in which participants who studied a list of cue-target pairs twice recalled "fewer" targets than a group who studied the pairs only once. Words within a pair rhymed and across pairs, the target words were drawn from a small set of categories. In the repetition condition, the pairs were initially presented in a random order and then presented a second time blocked by the category of the target words. In the single presentation condition, the pairs were presented only in the blocked order. Participants in the former condition recalled fewer target words on a free recall test despite having seen the word pairs twice (the negative repetition effect). The encoding conditions necessary to produce this effect were examined in 4 experiments. Presenting the repetitions in a single study list elicited the negative repetition effect in free and category-cued recall. However, eliminating the strong within-trial, rhyme relationship eliminated the effect in both tests. Finally, presenting a disorganized but unrelated set of rhyming word pairs as List 1 reduced recall (relative to the single-presentation condition) to the same degree as the repetition condition. The negative repetition effect is due to reduced interitem relational processing during the presentation of the organized list (or half list), a reduction that requires a competing within-target relationship but can be induced by an unrelated as well as identical set of word pairs.

Research suggests that spaced learning, compared with massed learning, results in superior long-term retention (the spacing effect). Son (2010) identified a potentially important moderator of the spacing effect: metacognitive control. Specifically, when participants chose massed restudy but were instead forced to space the restudy, the spacing effect disappeared in adults (or was reduced in children). This suggests spacing is less effective (or possibly ineffective) if implemented against the wishes of the learner. A closer examination of this paradigm, however, reveals that item-selection issues might alternatively explain the disappearance of the spacing effect. In the current experiments, we replicated the original design demonstrating that an item-selection confound is operating. Furthermore, relative to a more appropriate baseline, the spacing effect was significant and of the same size whether participants' restudy choices were honored or violated. In this paradigm, metacognitive control does not appear to moderate the spacing effect.

The reniform nematode (Rotylenchulus reniformis) is a sedentary semi-endoparasitic species that is pathogenic on many row crops, fruits, and vegetables. Here, the authors present a draft genome assembly of R. reniformis using small- and large-insert libraries sequenced on the Illumina GAIIx and MiSeq platforms.

A fundamental property of human memory is that repetition enhances memory. Peterson and Mulligan (2012) recently documented a surprising "negative repetition effect," in which participants who studied a list of cue-target pairs twice recalled fewer targets than a group who studied the pairs only once. Words within a pair rhymed, and across pairs, the target words were drawn from a small set of categories. In the repetition condition, the pairs were initially presented in a random order and then presented a 2nd time blocked by the category of the target words. In the single presentation condition, the pairs were presented only in the blocked order. Participants in the former condition recalled fewer target words on a free recall test despite having seen the word pairs twice (the negative repetition effect). This phenomenon is explored in a series of 5 experiments assessing 3 theoretical accounts of the effect. The experiments demonstrate that the negative repetition effect generalizes over multiple encoding conditions (reading and generative encoding), over different memory tests (free and cued recall), and over delay (5 min and 2 days). The results argue against a retrieval account and a levels-of-processing account but are consistent with the item-specific--relational account, the account upon which the effect was initially predicated.

Across 3 experiments, we investigated the factors that dictate when taking a test improves subsequent memory performance (the "testing effect"). In Experiment 1, participants retrieving a set of targets during a retrieval practice phase ultimately recalled fewer of those targets compared with a group of participants who studied the targets twice, a "negative" testing effect. In Experiments 2 and 3, theoretically motivated modifications to the basic design of Experiment 1 reversed this pattern, demonstrating the more typical positive testing effect. The results from all 3 experiments were predicted by the multifactor account, an explanatory account applied to the "generation effect" (improved memory for self-generated material), which details why generation typically improves memory, as well as those conditions under which generation can impair memory performance. These results suggest the testing effect and the generation effect may be understood within a common framework.