Frequency and consistency effects in a pure surface dyslexic patient.

Data are presented from a neurological patient (M.P.) with an acquired deficit for naming words with atypical spelling-sound correspondences. In Experiment 1, the degree of consistency within neighborhoods of orthographically similar words had a parallel impact on M.P.'s pronunciations of regular and irregular words and nonwords. This result is more compatible with models in which the same basic procedure, sensitive in a graded fashion to both frequency and consistency, computes pronunciations for all types of letter strings than it is with models postulating separate lexical and nonlexical mechanisms. In Experiment 2, both correct and regularized pronunciations of exception words yielded response times significantly modulated by word frequency, a finding not predicted by an current model. Neuropsychological observations provide an important additional source of evidence regarding models of cognitive function.