The two chapters of this monograph deal with the issue of the existence of a perceptual grammar that influences reading proficiency, particularly initial reading proficiency. The first chapter indicates the importance of studying reading and writing in terms of readers' and writers' knowledge of visuo-spatial processing rules. It discusses research into the processing of single shapes, the processing of arrays of shapes, and the production of shapes, and it suggests some readily testable hypotheses relating to the grammar of two-dimensional space. The suggested hypotheses deal with five areas: (1) mirror image confusions and writing reversals, (2) internal (mind's eye) scanning, (3) differences between production and recognition of graphic symbols, (4) readers' use of Cartesian spatial rules, and (5) low versus high skills. The second chapter describes Lila Ghent Braine's work indicating that children have a concept of "right-side-up" different from that of adults and discusses evidence that this concept contributes to children's rotation errors in copying symbols. It also discusses factors that contribute to children's mirror image confusions, outlines some practical implications, and offers hypotheses about reasons for the persisting orientation errors of children who have difficulty learning to read. (GT)