Abstract
Crowding refers to impairment in target identification due to the proximity of adjacent objects, and likely reflects inappropriate feature integration. It is the major factor leading to compromised peripheral reading performance. Here, we examined whether crowding can be remediated with dynamic presentation. The dynamic components were introduced through zoom mimicking "zooming" in or out on a document. Specifically, we varied letter size monotonically while maintaining center-to-center letter separation. Although the spatial extent of crowding is size independent above recognition level (Pelli, Palomares & Majaj, 2004), we predict that the coherent expanding/contracting motion within each letter will facilitate feature separation between letters and feature integration within letters, and in turn reduce crowding. We expect greater benefits for smaller zoom ranges and reduced/negative benefits for larger zoom ranges due to spatial and temporal limits. Four subjects identified the middle flanked letters (1° print size) in random strings of three letters presented at 10° below fixation. Performance was measured at 6 letter separations (ranging from 0.8 to 3.2°). The spatial extent of crowding, calculated based on the letter separations yielding 80% accuracy, was obtained for five zoom ranges (0° (size remaining at 1°), 0.125° (size varying between 0.875° and 1°), 0.25°, 0.5°, 0.75°), two zoom directions (inward, outward), and two durations (222ms, 444ms). For each combination of zoom direction and duration, the zoom range corresponding to the smallest spatial extent of crowding (the peak benefit) was determined. Averaged across subjects, the peak benefit (~10% reduction in spatial extent of crowding) was found at the zoom range of 0.22° for inward zooming at 222ms (p = 0.014). The benefits were less pronounced or absent for the longer duration and for outward zooming. The results suggest that crowding in peripheral vision can be alleviated with dynamic presentation which likely facilitates target-flanker feature separation and integration.
Meeting abstract presented at VSS 2013