A single-system interpretation of dissociations between recognition and categorization in a task involving object-like stimuli.

In previous research (Reed, Squire, Patalano, Smith, & Jonides, 1999), amnesic patients performed at near normal levels in a categorization task involving stimuli with discrete features, but showed impaired recall of the features. These results were taken as evidence of the existence of separate memory systems for categorization and recall/recognition. The present research addresses a single-system account of this dissociation. In Experiment 1, results closely matching the dissociation pattern were obtained when normal participants' classification and recognition performance was tested either immediately or after a week delay. In addition, formal modeling of the data suggested that participants use only a few of the dimensions in the categorization task, whereas they must use many dimensions in the cued-recall task. In Experiment 2, we found that many participants could perform the categorization task without any exposure to the training sequence. These results suggest that different memory demands across the two tasks may be responsible for the observed dissociation--separate memory systems are not necessarily involved.