Does Sleep Improve Your Grammar? : Preferential Consolidation of Arbitrary Components of New Linguistic Knowledge

We examined the role of sleep-related memory consolidation processes in learning new form-meaning mappings. Specifically, we examined a Complementary Learning Systems account, which implies that sleep-related consolidation should be more beneficial for new hippocampally dependent arbitrary mappings (e.g. new vocabulary items) relative to new systematic mappings (e.g. grammatical regularities), which can be better encoded neocortically. The hypothesis was tested using a novel language with an artificial grammatical gender system. Stem-referent mappings implemented arbitrary aspects of the new language, and determiner/suffix+natural gender mappings implemented systematic aspects (e.g. tib scoiffesh + ballerina, tib mofeem + bride; ked jorool + cowboy, ked heefaff + priest). Importantly, the determiner-gender and the suffix-gender mappings varied in complexity and salience, thus providing a range of opportunities to detect beneficial effects of sleep for this type of mapping. Participants were trained on the new language using a word-picture matching task, and were tested after a 2-hour delay which included sleep or wakefulness. Participants in the sleep group outperformed participants in the wake group on tests assessing memory for the arbitrary aspects of the new mappings (individual vocabulary items), whereas we saw no evidence of a sleep benefit in any of the tests assessing memory for the systematic aspects of the new mappings: Participants in both groups extracted the salient determiner-natural gender mapping, but not the more complex suffix-natural gender mapping. The data support the predictions of the complementary systems account and highlight the importance of the arbitrariness/systematicity dimension in the consolidation process for declarative memories

The differential effects of fluency due to repetition and fluency due to color contrast on judgments of truth

Two experiments contrast the effects of fluency due to repetition and fluency due to color contrast on judgments of truth, after participants learn to associate high levels of fluency with falseness (i.e., a reversal of the fluency-truth link). Experiment 1 shows that the interpretation of fluency as a sign of truth is harder to reverse when learning is promoted with repetition rather than with perceptual fluency. Experiment 2 shows that when color contrast and repetition are manipulated orthogonally, the reversal of the truth effect learned with color contrast does not generalize to repetition. These results suggest specificities in the processing experiences generated by different sources of fluency, and that their influences can be separated in contexts that allow the contrast of their distinctive features. We interpret and discuss these results in light of the research addressing the convergence vs. dissociation of the effects elicited by different fluency sources