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Perceiving the motion of an object is thought to involve two stages: Local motion energy is measured at each point in space, and these signals are then pooled across space to build coherent global motion. There are several theories of how local-to-global pooling occurs, but they all predict that global motion perception is a continuous process, such that increasing the strength of motion energy should gradually increase the precision of perceived motion directions. We test this prediction against the alternative that global motion perception is discrete: Motion is either perceived with high precision or fails to be perceived altogether. Data from human observers provides clear evidence that, whereas pooling local motion energy is continuous, the segmentation of local signals into coherent global motion patterns is a discrete process. This result adds motion perception to the growing list of processes that exhibit evidence of all-or-none visual awareness. Public Significance StatementVisual perception requires that objects are isolated from other objects, a process that is accomplished in part by analyzing motion energy across space. For example, although individual parts of a running dog may be moving in many directions at any moment, all of them share motion energy in the direction he's running, which helps the visual system to build the perception of a coherently moving object. This global motion process develops early in life, and deficits in it have been identified in disorders including autism, dyslexia, and schizophrenia. Whereas current theories of global motion perception predict that motion perception is analog, taking on any value from weak to strong, here we show that it is discrete: coherent motion is either perceived nearly perfectly, or not at all. This finding suggests that current models of global motion perception, and theories of why deficits in this process occur, may require substantial revision.

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SUMMARYView-based matching theories of orientation suggest that mobile organisms encode a visual memory consisting of a visual panorama from a target location and maneuver to reduce discrepancy between current visual perception and this stored visual memory to return to a location. Recent success of such theories to explain the orientation behavior of insects and birds raises questions regarding the extent to which such an explanation generalizes to other species. In the present study, we attempted to determine the extent to which such view-based matching theories may explain the orientation behavior of a mammalian species (in this case adult humans). We modified a traditional enclosure orientation task so that it involved only the use of the haptic sense. The use of a haptic orientation task to investigate the extent to which view-based matching theories may explain the orientation behavior of adult humans appeared ideal because it provided an opportunity for us to explicitly prohibit the use of vision. Specifically, we trained disoriented and blindfolded human participants to search by touch for a target object hidden in one of four locations marked by distinctive textural cues located on top of four discrete landmarks arranged in a rectangular array. Following training, we removed the distinctive textural cues and probed the extent to which participants learned the geometry of the landmark array. In the absence of vision and the trained textural cues, participants showed evidence that they learned the geometry of the landmark array. Such evidence cannot be explained by an appeal to view-based matching strategies and is consistent with explanations of spatial orientation related to the incidental learning of environmental geometry.

People vary in their performance on visual working memory tasks, and these individual differences covary with a wide range of higher-level cognitive processes including fluid intelligence. Performance also varies across study displays, purportedly driven by both low- and higher-level processes. Understanding what causes these sources of systematic variability has been crucial for developing theories of working memory. However, here we find that all such variability in performance on a test of visual working memory can be accounted for by concurrent variability in visual iconic memory: A person with relatively high working memory capacity will have high iconic memory capacity, and a particularly easy working memory display will also be easy under iconic memory conditions. These results are supported by a nonparametric factor analysis and hierarchical Bayesian model comparison. In a second experiment the relationship between iconic and working memory holds even when they are measured with substantially different experimental paradigms, and a third experiment suggests that the relationship between tests of iconic and working memory is driven by mechanisms other than iconic or working memory storage, such as variation in perceptual or attentional processes.