One has to be extraordinarily patient to be a sounding board. One must being willing to follow long lines of errant reasoning just to allow a student to abandon a fruitless line of reasoning on his own. Computers are easily programmed to allow a student to create detailed representations of his thinking, and to allow him to pursue or modify that line of thinking. One must be willing to allow students to pose their own answers and investigate their own thoughts. Computers can exhaustively capture whatever options students generate, letting the students pursue them as they wish.
Computer systems acting as sounding boards serve as design tools for thinking.
They can enable a student to capture the structure of his thought, help him focus on some part of the structure, and prod him with critical questions about that part. Permitted to speculate with a someone who is making helpful comments or suggestions, students can become, in effect, their own teachers. This goal underlies the Learning by Reflection Architecture.