Abstract
One theory proposed to account for the remarkable capacity and fidelity of visual memory is that visual memories are supported by an underlying structure of conceptual knowledge around which visual information is organized. However, some findings of visual memory learned in visual search tasks are not well explained by this theory. This study examines the importance of episodic, task-relevant, visual information in the organizational structure of visual memory. In two experiments, participants learned 36 target objects (750 ms presentation) in serial presentation search tasks, followed by additional searches containing varying numbers of new exemplars of the targets to introduce retroactive interference for the original search targets. Following the search trials, participants completed a 2-AFC memory test. The critical difference between the two experiments was the form of search instructions given. In Experiment 1, search instructions identified targets by color and conceptual category, making a perceptual feature, (i.e., color), relevant to the task, whereas in Experiment 2, the target was defined by the conceptual category alone making the perceptual feature irrelevant. In Experiment 1, memory test results showed that new exemplars that matched learned objects on both color and conceptual category induced more interference (80%) than those matched on conceptual category alone (87%). Experiment 2, in contrast, showed that new exemplar objects that matched only on conceptual category induced the same amount of interference (78%) as those matched on both color and conceptual category (77%). Results indicate that when made task-relevant, perceptual, as well as conceptual, information contributes to the organization of visual long-term memory. However, when made episodically non-relevant, perceptual information does not contribute to memory organization, and memory defaults to conceptual category organization. This finding supports a theory of an episodically defined organizational structure in visual long-term memory that is overlaid upon an underlying conceptual structure.
Meeting abstract presented at VSS 2015