Caroline Myers¹, Justin Halberda¹; ¹Johns Hopkins University

Which forms of memory truly depend on sensory codes, and which do not? Iconic memory depends on a sensory code - it preserves a sensory trace that is rapidly overwritten by subsequent visual input. Some contemporary sensory-recruitment accounts of visual working memory (VWM) suggest that VWM may depend on a sensory code as well - e.g., early perceptual areas may be recruited to maintain activity related to a remembered item. Here we investigated interference effects on Iconic and VWM using matched orientation-discrimination tasks with and without dynamic spatially overlapping visual masks. In both experiments, participants judged the direction of a small orientation change between a sample and test grating. Critically, the very same masks were used across experiments, allowing us to isolate the level at which interference occurs for each. Fitting psychometric functions to the data revealed that Iconic and VWM exhibit qualitatively different patterns of interference. Whereas observers’ precision and guess rate in the VWM task were robust to the masking manipulation, performance in the Iconic memory task was substantially impacted. These divergent signatures demonstrate that the two forms of memory rely on distinct representational formats: one that is overwritten by incoming sensory input, and one that is not. Together, these results offer a direct behavioral dissociation between Iconic and VWM, advancing a representational account in which Iconic memory is genuinely sensory while VWM operates at a more insulated, non-sensory level of the visual system.