Lexical decision performances in P-type dyslexic, L-type dyslexic, and normal reading boys.

Lexical decision performances in P-type dyslexic, L-type dyslexic, and normal reading boys were investigated using three-letter and four-letter words (familiar words) and nonwords presented in the central visual field. For words, P-type dyslexics displayed significantly longer latencies for four-letter than for three-letter word decisions, whereas L-type dyslexics and normal readers did not. For nonwords, all subject groups showed significantly larger mean latencies for four-letter than for three-letter nonword decisions. In general, the error data corresponded to the latency data. L-type dyslexics, however, made more errors during four-letter words than during three-letter words, although they had similar latencies in both conditions. The results are discussed with reference to the hypothesis that P-type dyslexics would use a sequential processing mode for reading familiar words, whereas L-type dyslexics would employ a parallel processing mode for reading familiar words.