This study demonstrates a manipulation that has opposite effects on old/new recognition and source monitoring. Deep processing of target items improved performance on an old/new recognition test in which subjects were to discriminate between targets and new distractors, but it impaired performance on a source monitoring test in which subjects were to discriminate between targets and distractors that had also been deeply processed during the experimental session. We argue that the relationship between old/new recognition and source monitoring varies with the specifics of the situation. The aspects of memories that support recognition judgments are not necessarily the same as those that support source monitoring judgments, and memory performance is the joint product of what is stored in memory and how memory is tested.According to the source monitoring model, event memories are attributed to particular sources in one's past experience by means of decision processes performed (often without awareness) during remembering (see, e.g., Hashtroudi, Johnson, & Chrosniak, 1989;Johnson, 1988;Lindsay & Johnson, 1987;Lindsay, Johnson, & Kwon, 1990). The term source refers to a variety of attributes that, collectively, specify the conditions under which an event memory was acquired (e.g., its spatial and temporal context, medium, modality, etc.) . Source monitoring processes are involved in the remembering of such things as where and when an event occurred, how it was perceived, and who and what were involved in it. Reality monitoring decisions-discriminations between memories of actual perceived events and memories of imagined, internally generated events-represent a particularly intriguing type of source discrimination (Johnson & Raye, 1981).Support for the hypothesis that memories are attributed to particular sources via decision-making during remembering comes from a variety of studies that have demonstrated effects of memory content on source monitoring accuracy. Most of these studies have consisted of a study phase, during which subjects receive information from different sources, followed by a test phase, in which subjects are tested on their ability to identify the source of particular test items. In general, we have found that manipulations that increase the similarity between to-bediscriminated sources lower source monitoring perforCorrespondence concerning this manuscript may be addressed to Marcia Johnson, Department of Psychology, Green Hall, Princeton University, Princeton, NJ 08544, or to D. Stephen Lindsay, Department of Psychology, McMaster University, Hamilton, Ontario L8S 4K I, Canada.mance (see Johnson, 1988, andJohnson &Raye, 1981, for reviews of these studies and discussions of their relation to other areas of the memory literature).What is the relationship between source monitoring and old/new recognition? Both tasks require that subjects discriminate between test items on the basis of their prior experience with those items. Old/new recognition tests require subjects to differentiate between items that...