This article has two purposes. The first is to describe four theoretical models of yes-no recognition memory and present their associated measures of discrimination and response bias. These models are then applied to a set of data from normal subjects to determine which pairs of discrimination and bias indices show independence between discrimination and bias. The following models demonstrated independence: a two-high-threshold model, a signal detection model with normal distributions using d' and C (rather than beta), and a signal detection model with logistic distributions and a bias measure analogous to C. C is defined as the distance of criterion from the intersection of the two underlying distributions. The second purpose is to use the indices from the acceptable models to characterize recognition memory deficits in dementia and amnesia. Young normal subjects, Alzheimer's disease patients, and parkinsonian dementia patients were tested with picture recognition tasks with repeated study-test trials. Huntington's disease patients, mixed etiology amnesics, and age-matched normals were tested by Butters, Wolfe, Martone, Granholm, and Cermak (1985) using the same paradigm with word stimuli. Demented and amnesic patients produced distinctly different patterns of abnormal memory performance. Both groups of demented patients showed poor discrimination and abnormally liberal response bias for words (Huntington's disease) and pictures (Alzheimer's disease and parkinsonian dementia), whereas the amnesic patients showed the worst discrimination but normal response bias for words. Although both signal detection theory and two-high-threshold discrimination parameters showed identical results, the bias measure from the two-high-threshold model was more sensitive to change than the bias measure (C) from signal detection theory. Three major points are emphasized. First, any index of recognition memory performance assumes an underlying model. Second, even acceptable models can lead to different conclusions about patterns of learning and forgetting. Third, efforts to characterize and ameliorate abnormal memory should address both discrimination and bias deficits.

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This paper reports perceptual identification thresholds for 150 pictures from the 1980 Snodgrass and Vanderwart picture set. These pictures were fragmented and presented on the Apple Macintosh microcomputer in a picture-fragment completion task in which identification thresholds were obtained at three phases of learning: Train (initial presentation), New (initial presentation after training on a different set), and Old (repeated presentation of the Train set). Pictures were divided into five sets of two subsets of 15 pictures each, which served alternately as the Train and New sets. A total of 100 subjects participated in the task, with 10 subjects assigned to each subset. Individual thresholds for each picture at each phase of learning are presented, along with the fragmented pictures identified by 35% of the subjects across the Train and New learning phases. This set of fragmented pictures is provided for use in experiments in which a single level of fragmented image is presented for identification after a priming phase. Correlations between the Snodgrass and Vanderwart norms and identification thresholds at the three phases of learning are also reported.

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A set of procedures implemented in Microsoft BASIC is described that creates fragmented versions of pictures scanned into the Apple Macintosh, stores them as resource files, and presents them in a computerized perceptual memory test. A total of 150 pictures were selected from the Snodgrass and Vanderwart (1980) set for fragmentation. The perceptual memory test provides for five forms of 30 pictures each, divided into two sets of 15 that serve alternately as the training or old set and the new set. A training set of 15 pictures is presented for identification during the first (training) phase of the test. The second (test) phase presents the training pictures again, randomly mixed with 15 new pictures for identification. The performance of 100 subjects on the memory test is presented, along with results for each form. Overall, subjects showed improvement on the task with practice (skill learning), indexed by a decrease in thresholds from the training set to the new set. Subjects also showed large savings for the repeated pictures (perceptual learning), indexed by a decrease in thresholds from the new to the old set. This paper describes a set of procedures for fragmenting picture stimuli, storing them as resource files, and presenting them in a computerized test of perceptual learning that runs on an Apple Macintosh Plus. The test follows the GoUin Picture Test (Gollin, 1960) in spirit. In the Gollin test, subjects are shown a series of pictures from which fragments have been deleted, starting with the most fragmented level. Increasingly more complete versions of each picture are shown until all pictures can be identified. Subjects are then retested on the old items to measure perceptual memory. Although the test was initially developed for use with children, it has been used extensively with clinical populations (e.g., Corkin, 1982), following the demonstration by Warrington and Weiskrantz (1968) that amnesic patients show substantial learning and retention as measured by decreased thresholds for repeated pictures after a delay of as long as 3 months. This preserved learning ability in amnesics-along with demonstrations in normal subjects that effects of many variables are dissociated in perceptual, compared with episodic, learning tasks-has led several investigators to postulate