Similar criticisms apply to claims from single-subject studies of treatment for some ´class´ of lexical disorders. For example, Partz (1986) described treatment of ´deep dyslexia´ that involved re-teaching sound—spelling correspondences. Their patient (like P.M. noted earlier) improved in oral reading of words (and non-words) using this strategy. But improved oral reading would be a useful gain only for those patients in whom the problem that underlies the behaviours classified as ´deep dyslexia´ stems from damage to the phonological output lexicon.