Most Russian work follows Pavlov's theory that schizophrenia is due to excessive protective inhibition in the cerebral cortex and is devoted to demonstrating in detail the truth of this hypothesis. According to a large number of reports, schizophrenics differ from normals in orientation reactions, sympathetic reactivity, EEG, conditionability, and word association tests. There appear to be 2 groups of schizophrenics: a majority group in whom sympathetic tone and reactivity are low, and a minority group in whom these are high.