It seems reasonable to assume that without the fast, accurate guidance of a central control mechanism, the brain might show the kinds of symptoms which we see in dyslexia. For instance, poor allocation of neural space and insufficient arousal of the left hemisphere might encourage inappropriate reliance on right hemispheric strategies during language and number processing. Without the sustained attention and focus provided by a robust corpus callosum, you would expect the kind of distractibility and inattentiveness so often seen in dyslectic children. Considering the extremely fine and rapid interhemispheric transfer of information necessary for smooth ocular functioning, it is reasonable to assume that slow or degraded transfer of input across the hemispheres might result in poor ocular motor skills. By the age of ten, however, when myelinization is virtually complete, normals have no trouble with this.
Dyslectics score like everybody else at age six, but they still score poorly in adulthood.
People without a corpus callosum cannot do it at all. One of the most interesting pieces of evidence comes from some work done with high speed photography which showed that dyslectics' movements on one side of the body are out of synchrony with movements on the other. For instance, if a dyslectic child hears a click, his right side turns toward the sound a fraction of a second before his left side turns. When he blinks, the right eyelid starts down before the left. When he smiles, the right side of his mouth turns up before the left one.