Finding the "odd one out": Memory color effects and the logic of appearance

Can what we know change what we see? A line of research stretching back nearly a century suggests that knowing an object's canonical color can alter its visual appearance, such that objectively gray bananas appear to be tinged with yellow, and objectively orange hearts appear redder than they really are. Such "memory color" effects have constituted the strongest and most complete evidence that basic sensory processing can be penetrated by higher-level knowledge, and have contributed to theories of object perception in psychology, neuroscience, and philosophy. Are such phenomena truly perceptual? Or could they instead reflect shifts in judgments and responses without altering online color perception? Here, we take a novel approach to this question by exploiting a "logic" that is inherent in visual processing but that higher-level cognition often cannot follow. In four experiments spanning both classical and contemporary work, we exhaust the predictions of memory color theories, by exploring scenarios where memory color accounts generate tortuous and difficult-to-grasp hypotheses that should nevertheless be easily accommodated by visual processing. We show that such conditions eliminate or even reverse memory color effects in ways unaccounted-for by their underlying theories-especially in a novel "odd one out" paradigm that may help distinguish visual appearance from higher-level judgment in a powerful and general way. We suggest that prior knowledge can influence color judgments in real and robust ways, but that such influences may not truly reflect changes in visual appearance per se. We further discuss the general utility of this approach for isolating perception from judgment, both for memory color effects and beyond.