Abstract
Because vision blends seamlessly into memory, vision's imprint can yield unique insights into memory processes. To exploit this possibility we examined errors in short term episodic recognition and source memory for simple visual stimuli. On each trial of three experiments, subjects saw and had to remember a trio of sequentially-presented compound sinusoidal gratings. The study items were followed quickly by a probe grating. On some trials, the probe matched one of three study items; on other trials, the probe was novel. Subjects made source memory judgments, identifying the serial position of the study item that matched the probe (Experiments 1 and 2), or made old-new, recognition judgments (Experiment 3). About 25% of correct recognitions were accompanied by incorrect source identifications. Such errors were deterministic: When subjects misidentified serial position, they still retained partial information about the actual memory source, namely its perceptual or serial order characteristics. ROCs for recognition memory were generated from all three experiments, either by aggregating source identification responses (Experiments 1 and 2), or directly from recognition responses (Experiment 3). The three sets of recognition ROCs were very similar to one another, suggesting that memory loses little information in generating recognition judgements from stored exemplars. Slopes of zROCs for old-new judgments were consistently >1, indicating that distributions on old and new trials had different variances. This result could be easily explained within a summed-similarity model for visual memory (NeMO; Kahana & Sekuler, Vision Research 2002).
Supported by AFOSR Award F49620-03-1-0376 and NIH grant MH068404