Every time we open our eyes, our visual system is overloaded with information. This is especially true in the peripheral visual field: Although we feel that we are aware of the details of individual objects in our periphery, the number and density of objects in natural scenes means that we are unable to perceive detailed information such as identity or quantity. This inability to scrutinize objects in the periphery when other objects are present is called visual crowding. Counterintuitively, crowding may be beneficial. A number of models have emphasized that crowding can improve processing efficiency or allow us to detect statistical regularities in natural scenes--tasks that are fundamental to all aspects of visual perception. Despite the existence of a unique psychophysical definition for crowding, and its clear importance in visual processing, there are major gaps in our understanding of where in the visual hierarchy crowding occurs, the sorts of objects on which it operates, and the underlying neural mechanism that causes crowding. With funding from the National Science Foundation, Dr. David Whitney and his colleagues at the University of California, Davis, are pursuing two major research goals. First, by measuring behavioral performance, Dr. Whitney will test the hypothesis that crowding operates independently at multiple levels of visual analysis, for low-level visual features such as contours or gratings, and also for high-level objects such as faces. Second, Dr. Whitney's team will isolate and identify the neural mechanisms that mediate both low and high-level crowding using a non-invasive brain imaging method known as fMRI-adaptation.
Understanding visual crowding is fundamental to understanding most other aspects of visual perception. Every natural scene we look at is densely filled with objects, but only a very few of these can be simultaneously scrutinized, largely because visual crowding prevents the visual system from having access to all the details at once. Perception, therefore, is subject to the costs (and benefits) of crowding. Because human vision is perhaps the most thoroughly examined operational visual system, investigating the impact of crowding on human perception will be important in developing a realistic artificial visual system in the future. More broadly, understanding the limits of human spatial vision, including crowding, has the power to improve a range of applications including data visualization (e.g., crowding interferes with visualizing abnormalities on an x-ray), advertising (e.g., too many words or images on a billboard causes car accidents), computer graphics (e.g., too many flashing icons on a website becomes ineffective), visual art and movies (e.g., do not crowd the star actor with too many other nearby faces), and a host of other applications. In addition to the broader impacts noted above, this proposal will support the training of a graduate student. Moreover, Dr. Whitney will establish a unique outreach program in local high schools, with predominantly Hispanic populations, that will use art as a way to introduce visual neuroscience research questions and methods. The educational outreach program is specifically aimed at stimulating interest and increasing the participation of under-represented groups in basic science research.
