When is Motion ‘Motion’?

Abstract

Examples of visual motion have become more and more abstract over the years, leading up to ‘third-order’ stimuli where direction is actually determined by the observer through top–down attention. But how far can this be pushed—are there motion stimuli that are yet more arbitrary and abstract? Actually, there is a broad class of ‘conceptual motion’ stimuli—things like a moving grating of faces, or a shifting pattern of words—that are perfect analogs to traditional ‘perceptual motion’ stimuli, solvable by the same motion computation and for which observers can readily make direction-of-motion judgments. Interestingly though, these do not produce a sensation of motion (among other automatic consequences of motion detection). Here we compare a luminance-based perceptual motion stimulus to a semantic-based conceptual motion stimulus to contrast the psychophysical hallmarks of these motion categories.