In an ongoing study of 102 children, aged 6-17 years old, who have been prevously labelled by clinicians as autistic or schizonphrenic, matching these subjects with young normal children who have the same mean length of utterance (MLU) suggests that the psychotic children employ normal mechanisms of syntax acquisition, and have vocabulary and perceptual development commensurate with their level of grammatical skill. This apparently normal but extremely delayed developmental progress is not indexed by present diagnostic schemes, however. Three frequently used schemes of diagnosis, from Rutter (autism), Rimland (autism), and Creak (schizophrenia) -- all based largely on parental recall of early childhood symptoms and behavior -- serve to group psychotic children's language and perception skills less well than simple tripartite divisions (low, middle, high) of scores on the Frostig visual perception test, and the Peabody Picture Vocabulary test. While all Fs on the Peabody and Frostig tripartite divisions are significant, there is only one significant F across the diagnostic categories (i) autistic (ii) schizophrenic (iii) uncategorized psychotic. Fein has recently found the presence of specific auditory brainstem dysfunction in half of a sample of children diagnosed as autistic: this dysfunction was associated with specific observed behavioral patterns, but not with language performance. To further explore these findings and the findings of our current work, we therefore propose to replicate our language and perception development study, partitioning tested cognitive and observed behavioral skill performance both by diagnostically determined groups as well as by groups formed by neurological analysis (EEG/soft sign), and tests of sensory responsiveness (evoked potentials/sensory stimuli reactions).