A hypothesized hierarchy of tasks in the development of tactual discrimination (an essential skill for reading) was tested in 60 blind primary level children. For five braille and five Optacon (optical to tactile converter) sequences, Ss were asked to identify the different stimulus from the four presented. Scalogram analysis was used to examine the results using a variety of criteria of mastery for all tasks. Results validated the hypothesized sequence of tasks and indicated that many first grade and most second grade Ss completed at least half of the simple discriminations given on the Optacon. Data supported the suggested use of raised line forms in Optacon readiness materials. (Four appendixes include a 40-page review of the literature.) (CL)