Legibility of Chinese characters in peripheral vision and the top-down influences on crowding.

Written Chinese is distinct from alphabetic languages because of its enormous number of characters with a great range of spatial complexities (stroke numbers). In this study we investigated the impact of spatial complexity on legibility of Chinese characters as well as associated crowding in peripheral vision. Our results showed that for isolated characters, threshold sizes of complex characters increased faster with retinal eccentricity than did those of simple characters, suggesting possible "within-character" crowding among parts of complex Chinese characters. However, such "within-character" crowding was rendered negligible by strong "between-character" crowding introduced by flankers. When the target and flankers belonged to different complexity groups, the intensity and extent of crowding were greatly reduced, which could be explained by top-down influences as well as lower-level mechanisms. We suggest that crowding can be attributed to multiple mechanisms at different levels of visual processing.