Observations linking laterality of hand or eye with difficulty in learning to read have a long history. Samuel Orton is usually credited (if that is the right word) with the idea that reading disability is associated with anomalies of so-called cerebral dominance (Orton, 1925). This term refers to the idea that one half of the brain takes a leading role in specific functions. The notion of cerebral dominance current at the time, propagated with respect to stuttering in particular (Travis & Johnson, 1934), was that one cerebral hemisphere, almost always the left, was in some way dominant over its partner. There appeared also to be a tacit assumption that this state of affairs took some time to develop and that the lack of a strong preference for one hand or the other reflected an intervening or immature state of “sideness”. From here it was but a short step to arguing that incomplete lateralization at the level of the hand and/or eye reflected a failure of one hemisphere to develop dominance over the other. This idea became especially popular within the context of mirror-writing and mirror-reading.