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In recent years the brain systems which underlie and produce the phenomena called instinct have been delineated. For the first time the systems, which when stimulated cause either various kinds of pleasure or various types of negative avoiding, painful or fearful reactions, have been discovered and studied in great detail. Work has been accomplished on rats (16), cats (23), (1), monkeys (1), (7), dolphins (8), and in humans (20), (21), which has far-reaching implications for the systematic development of the theory of instincts.
In this paper the levels of discourse must be very carefully delineated to avoid confusion. Experiments using rats, cats, and monkeys involve extremely simple nervous systems compared with those of the human and of the dolphin. The phenomena elicited are completely reproducible. The responses to stimulation of the rat brain are simple and amazingly repetitive kinds of behavioral patterns: the cat introduced slightly greater variability; and the monkey steps up the complexity considerably. However, it is not until one investigates a brain comparable in size with that of the human that the full range of human complexity, which is dealt with in psychoanalysis, is achieved. The phenomena of speech, of writing, of love and hate of mental symbols, etc., do not appear in