Recent researches in the schizophrenias have led to the identification of systematic relationships between sensory, perceptual, and cognitive response parameters, on the one hand, and on the other, symptom variables and their interactions with "premorbid adjustment" and length of hospitalization variables.Certain psychological and physiological reaction patterns and the mechanisms which appear to underlie them are examined in various schizophrenic and nonschizophrenic groups. These response mechanisms, conceptualized as serving significant defensive and adaptive functions, are shown to assume quite different forms in clinically differentiable schizophrenic subtypes.