Story of Psychology - Morton Hunt [322]
At Yale in the 1950s, Delgado and several colleagues did equally impressive, if less theatrical, research with electrode implantations in rats and cats. By sending a weak current into a cat’s or rat’s amygdala—a part of the “limbic system” or ancient mammalian brain, a series of structures located between the thalamus and the cortex—they produced fear behavior. Later, Delgado and others did so with human patients during brain surgery. When one patient was receiving the current, he said he felt as if he had just been missed by a car, another as if “something horrible was about to happen” to her. The feelings ceased as soon as the current was turned off.32
A completely different kind of evidence supporting the limbic-system theory of the emotions was produced in the 1970s by J. E. Steiner, a developmental psychologist. He took pictures of newborn infants to whom, before their first feeding by breast or bottle, he gave water flavored sweet, sour, or bitter. The sweet water caused the babies to lick their lips, the sour water to purse them and wrinkle their noses, and the bitter water to open their mouths and spit or retch. Steiner then did the same with anencephalic newborns (anencephaly is a tragic anomaly in which the fetus develops no brain tissue above the brain stem; the newborn soon dies); they exhibited exactly the same facial expressions and reactions. Simple emotions and their facial expressions thus appear to be generated by the brain stem, although the responses are modified later, in normal children, by higher nervous centers as the children learn what is acceptable emotional behavior in their society.33
In the 1950s Magda Arnold, a Czech-born psychologist at Loyola University in Chicago (one of the few women to attain eminence in psychology before midcentury), and others proposed “arousal theory,” an integrated explanation of both motivation and emotion that held their origin to be the “reticular formation” (a network of neurons connecting the brain stem to the thalamus) and the limbic system.
Arousal theory, supported by research using electrode stimulation of the brain, holds that incoming stimuli “activate” parts of the reticular formation and limbic system, which alert the cortex and ready the creature for action.34 Sounds or smells, for instance, will awaken a sleeping animal; a baby’s whimper will bring its sleeping mother wide awake and on her feet in an instant. Such stimuli as deprivation of water, food, or air, or an increase in sex hormone levels, were also shown by electroencephalograms (EEGs)—brain recordings—to activate the reticular formation and, through it, to increase heart rate and overall activity.35 In sum, the theory envisioned the reticular formation as a regulatory device that, on receiving signals by the senses, turns on both physiological activity and emotional responses.
But as Phil Evans, senior lecturer in psychology at North East London Polytechnic, has ruefully said of arousal theory, “Few concepts in psychology have proven so bothersome and yet so superficially attractive.”36 For although it provides a neural explanation of both motivation and emotion, and makes sense of a wide array of data, it is too general. It presents only one dimension of emotion—the degree of arousal— which leaves unexplained the diversity of the emotions. Also, physiological measures of arousal like heart rate and skin conductance often fail