Dissociations among implicit and explicit memory tasks: the role of stimulus similarity

This article compares the effect of picture fragmentation level at study on performance on a variety of implicit and explicit memory tests. Consistent with previous research, a moderately fragmented study picture produced the most learning on the implicit memory task of picture fragment completion (Experiment 1) and speeded picture identification (Experiment 4). In contrast, an intact study picture produced the most learning on the implicit memory task of naming intact pictures (Experiment 3). These results suggest that performance on 2 implicit memory tasks can be dissociated by differences in visual similarity between the study and test forms of a stimulus. More surprising, parallel effects were observed in recognition memory. Recognition memory was best when fragmentation levels of the study and test pictures matched (Experiment 2) or were comparable (Experiment 1). In contrast to many results in the literature, recognition memory was acutely sensitive to surface form differences. We discuss the results in terms of 2 types of study-test similarity-stimulus similarity and process similarity.