Dissociations in Grammar Learning 1 Running Head: DISSOCIATIONS IN GRAMMAR LEARNING Dissociations of Grammaticality and Specific Similarity Effects in Artificial Grammar Learning

Three artificial grammar learning experiments investigate the memory processes underlying classification judgments. In Experiment 1, the effects of grammaticality, specific similarity and chunk frequency are found to be similar between classification and recognition. In Experiment 2a and 2b, instructions to exclude "old " and "similar " items under conditions that make conscious recollection difficult are found to dissociate grammaticality and similarity effects in classification. Finally, dividing attention at test in Experiment 3 also dissociates these effects, but the pattern of data underlying the dissociation is different from Experiments 2a and 2b. On the basis of these results, it is concluded that grammaticality effects are based on automatic memory processes, whereas intentional uses of memory largely support the specific similarity effect. It is argued that these results are consistent with a dual-process model of classification, but inconsistent with unitary mechanism accounts. The experiments also indicate that chunk frequency has both implicit and explicit influences on classification judgments