Differences in perceptual processes of good and poor readers relevant to single word perception have been studied in a series of experiments. The major differences between good and poor readers have been shown to occur at the level of the single word; other differences occur in knowledge of spelling patterns and ability to make use of letters' positional redundancy (their tendency to occur very often in a given position) in words. To demonstrate knowledge of positional redundancy, subjects search for a target letter in a string of letters; data from experiments using this visual scanning task suggest that redundancy related to letter position alone is a strong differentiator of reading ability. Regardless of how much of the reading process is visually based and how much is based on phonology, considerable visual processing must precede a phonological stage. Other experiments have addressed a variety of topics, including brain hemispheric specialization in children's reading; differences between good and poor readers in memory processing, use of spatial redundancy, and use of distinctive letter features alone; and positional redundancy effects using novel nonalphabetic symbols. Current research is concerned with determining the relative information value of positional information alone and in conjunction with letter context information. (GW)