The interaction between environment and temperament is inordinately complex, of course, and it only gets more complex the more it is studied. All animals are shaped not only by their genes, but by the circumstances under which they develop; as the science writer Matt Ridley has put it, “Nature versus nurture is dead. Long live nature via nurture.” Mice and rats, we know, grow more neurons in the hippocampus when they are brought up in an enriched environment rather than in a standard laboratory cage. Rat pups removed from their nests and given more freedom to explore for a few minutes every day for the first three weeks of life show less anxiety and more exploratory behavior later. Rhesus monkey infants raised in an enriched environment, with a terrycloth-covered movable surrogate monkey and a terrycloth diaper covering a “water bed”—rather than in a standard environment, with a stationary surrogate and only a terrycloth diaper—do much better when they are tested later on a variety of problem-solving and motor tests. There is, as well, an interaction between an animal’s innate temperament and how it is raised. Those monkeys who do the best on subsequent testing are those who rate low on fearfulness during their first month of life and who are also reared in an enhanced environment. Those who do worst, on the other hand, are those who display a fearful temperament when very young and have no exposure to an enhanced environment.
Strong temperamental differences in young nonhuman as well as human infants, together with findings from studies of identical and nonidentical twins demonstrating a strong genetic influence on temperament, make it clear that biological factors are importantly involved in exuberant behavior. One of the most consistently implicated of these biological factors is dopamine, a neurotransmitter of ancient origins. Dopamine, one of many neurotransmitters in the brain responsible for the regulation of moods and motivated behaviors (others include, importantly, serotonin and norepinephrine), long predates our earliest mammalian ancestors; indeed, its existence can be traced back to mollusks and other invertebrates that lived more than half a billion years ago. Dopamine does many things: it heightens attention to unexpected happenings in the environment; it regulates movement; and, most critically here, dopamine is central to reward. Dopamine is released in the brain in response to behaviors of obvious evolutionary value such as obtaining food, drink, and sex. But the plunge downward on a roller coaster also increases dopamine, as does a win at gambling or a line of cocaine. Music, too, as we shall see, has a powerful effect. Brain imaging studies conducted while a person is listening to music show that there are increases in cerebral blood flow in the same reward areas of the brain that are active when food, sex, or highly addictive drugs are involved. (Music may also, like other inducers of positive mood, decrease activity in those regions of the brain associated with negative emotions, such as anxiety or revulsion.)
In the 1950s, James Olds and Peter Milner at McGill University in Canada carried out a famous series of experiments on the brain’s “pleasure center.” They placed an electrode deep into the brains of rats and demonstrated that rats will press a bar connected to the electrode in order to stimulate a particular area within the hypothalamus, a part of the brain crucial to, among other things, regulating reward and punishment. Indeed, rats find the pleasure so extraordinarily reinforcing they will press the bar thousands of times an hour and actually starve to death rather than stop. A major nerve pathway, which runs through this pleasure area of the brain, pours out dopamine when stimulated. Rats injected with drugs that block the effects of dopamine press the bar far less frequently.
Dopamine, which is concentrated in the frontal lobes of the brain and in the limbic system, or “emotional brain,” strongly influences the emotional system that motivates both exploratory and anticipatory behaviors. The anticipation of sex or food, of meeting up with a close friend, or of discovering or experiencing something new brings with it an expectation or hope that pleasure will follow. Expectation, in turn, motivates behaviors likely to lead to the desired outcome. The release of dopamine that accompanies both the anticipation and the consummation of these activities makes it more likely that the behaviors will be repeated.
Scientists believe that the brain’s sensitivity to dopamine is correlated with extraversion. If, for example, a drug that increases dopamine transmission is injected into the brain of a mouse, the animal will become more “outgoing” and exploratory. A mouse born without the genes necessary to make dopamine, on the other hand, becomes essentially catatonic, unable to take action. The dopamine-deprived mouse is as pervasively uninterested in its environment as the dopamine-enhanced mouse is actively curious.
Psychologists find that extraverts are exquisitely sensitive to rewards. Researchers at the University of Illinois at Urbana—Champaign, for example, studied individuals from thirty-nine countries and found that only those facets of Extraversion that are most linked to reward sensitivity—Affiliation (friendliness, enjoyment in the company of others); Ascendance (leadership and social dominance); Venturesomeness (seeking out of exciting, stimulating situations); and Social Interaction (preference for being with others)—cluster together on a single higher-order Extraversion factor. This factor, in turn, correlates strongly with positive emotion. It may well be that individuals who seek out novelty and adventure are biologically more likely to feel an intense rush from having done so and, therefore, are more likely to seek out novelty yet again.
Dopamine is strongly associated with positive affect and importantly implicated in its most pathological manifestation, acute mania. The staggeringly high level of physical energy and mental activation that, together with an abnormally excited mood, is so characteristic of mania creates an extreme state of mental and physical exuberance. Amphetamines promote the release of dopamine and inhibit its uptake; they usually produce hypomania if given to patients who have a genetic vulnerability to manic-depressive illness. So does the dopamine precursor L-dopa, which is used in the treatment of Parkinson’s disease. Likewise, drugs that increase dopamine levels tend to have an antidepressant effect. Antipsychotic medications, in turn, exert much of their therapeutic effect against mania by selectively blocking dopamine receptors in the brain.
There are specific areas in the brain particularly linked to pleasure and high mood, as well as to exploratory behavior. Greater activation in the left frontal area of the brain is associated with joyful emotions, for example, and is more common in highly uninhibited children and in adults who are unusually enthusiastic and energetic. The left frontal portion of the brain is associated with physical and cognitive behaviors involved in novelty-seeking and reward, and the left prefrontal cortex with the anticipation of pleasure. Neuroimaging studies show that photographs with highly interesting or positive content activate the left amygdala but not the right (the amygdala is involved in emotional processing and the formation of emotional memories). An individual with damage in the left frontal areas of the brain is more likely to be depressed and apathetic; damage or abnormal growths in the right frontal region of the brain, on the other hand, not uncommonly result in inappropriate laughter or actual mania. Recent brain imaging studies show that patients with manic-depressive illness are more likely to have a reduction in gray-matter volume in areas of the right prefrontal cortex than in the left.
In a 2003 study reported in Science, Carl Schwartz, Jerome Kagan, and their colleagues reported that at least one aspect of brain functioning associated with temperament is relatively consistent from infancy through early adulthood. They used functional magnetic resonance imaging (fMRI) techniques to measure the response of the amygdala to neutral expressions on either a novel face or a familiar one. Their subjects were young adults who, in the second year of their lives, had been categorized as having either an inhibited or uninhibited temperament. When shown novel faces, those who had been evaluated as inhibited at two years of age showed greater responses in both the left and right amygdala than those who had been categorized as uninhibited. There was no difference between the two groups when they were shown familiar faces. Kaga
n suggests that the amygdala is primarily responsive to novelty, rather than to a fear-inducing stimulus, and that exuberant individuals seek and enjoy new experiences in part because of their amygdalar chemistry (not because they are not fearful).
Exuberance is not only greatly influenced by the biological activity of the brain, it in turn exerts its own sway over mind and body. That effect is a salutary one. “A merry heart doeth good like a medicine,” says Proverbs, and mirth, wrote Robert Burton four hundred years ago in The Anatomy of Melancholy, is one of the true nepenthes: it “purgeth the blood, confirms health, causeth a fresh, pleasing, and fine colour … whets the wit, makes the body young, lively, and fit for any manner of employment.” The merrier the heart, alleged Burton, the longer the life. Modern science tends to support his contention: positive emotions such as joy act as breathers from stress and in doing so they help to restore physical and psychological health after draining or stressful times.
In one test of this idea, Barbara Fredrickson and her colleagues at the University of Michigan conducted an experiment in which they induced a high-arousal, negative emotional state in their research subjects. The experimenters measured the cardiovascular effects of the negative induction; they then followed up the negative induction with one that produced either a neutral mood, mild joy, sadness, or contentment. They found that subjects who received positive inductions, of joy or contentment, took far less time to return to their normal level of cardiovascular functioning than those who had not.
Shelley Taylor of the University of California at Los Angeles, along with others, suggests that positive attitudes such as optimism and the propensity to find benefit in difficult experiences—such as chronic or terminal illness, natural disaster, or being the parent of an acutely ill newborn—may improve the course and outcome of the illness or distress. Psychologists increasingly believe that positive emotions and expectations may improve the body’s immune functioning, make it more likely that an individual will act in healthy ways, and increase the chances of having better and more sustaining personal relationships. (A study of 180 nuns who had been asked when they were in their twenties to write brief autobiographical statements found that 24 percent of those who had expressed the most positive emotions had died by the age of eighty; in contrast, 54 percent of those who expressed the least positive emotions had died.) William Hazlitt wrote that our attachment to life depends upon our interest in it, that “passion, imagination, self-will, the sense of power, the very consciousness of our existence, bind us to life, and hold us fast in its chains, as by a magic spell.” Those who are exuberant or positive by nature hold on to life and move forward when many others cannot.
Positive emotions affect not only physical health but thinking and behavior as well. “Lively passions commonly attend a lively imagination,” wrote David Hume over 250 years ago, and his observation finds support in recent psychological research. Alice Isen at Cornell University has, with others, developed a variety of ways to temporarily induce elevated moods in experimental subjects in order to compare changes in their behavior and thinking with those of subjects whose moods have not been elevated. Methods used to evoke mood changes include music, film comedies, cartoons, and unexpected gifts or praise. Most of these inducers are relatively mild but the results are nonetheless striking. (It would perhaps require drugs, dance, or ecstatic music to provoke actual exuberance.) Those who have had their mood experimentally elevated are more likely to make decisions quickly and efficiently, to help others when given the opportunity, to speak more and faster, to be more sociable, and to take greater risks. They also more actively explore their surroundings and engage in a greater variety of activities. It is as if a dollop of galumphing had been injected into their brains.
Originality and fluency of thinking are particularly affected by changes in mood. This has been shown not only in mood induction studies but also in research that has looked at cognitive changes during mild manias. (Mild mania is almost always accompanied by a vivid elevation in mood; exuberance, as we shall see later, is a frequent feature of both mild and more severe manias.) Mood induction studies repeatedly show that individuals whose moods have been experimentally elevated give a larger number of responses, as well as a larger number of unusual responses, to neutral words presented during a word association task, a measure that is linked to creativity. (If, for example, a subject is asked to offer as many words as possible in response to the word “tulip,” both the number of words, and the number of unusual words, can be compared with the responses of thousands of others who have been given the same task.) They are also more likely to classify visual forms and verbal concepts in a global way than in a specific way. An individual in a positive mood tends to see the forest and the pattern among the trees; an individual who is in neither a positive nor a depressed mood picks out the trees. Someone who is depressed focuses in on the bark (and then notes, as well, where it is peeling). “Not by constraint or severity shall you have access to true wisdom, but by abandonment and childlike mirthfulness,” wrote Thoreau in his journal. “If you would know aught, be gay before it.”
In a typical study of positive mood induction, twenty-two eighth-grade students were given tests designed to assess creativity and problem-solving ability. One task required the students to come up with as many words as possible in response to the words “fruit” and “bird.” In the other, each child was given a box, some tacks, a candle, and a book of matches and asked to set up the candle vertically so that it could act as a lamp without dripping wax. Positive mood was induced in half of the students and a neutral mood in the other half. Those students in the positive mood group generated significantly more words than those in the neutral group (twenty-nine and sixteen words, respectively), and the words they generated were much more likely to be unusual. Seven out of eleven in the positive mood group were able to solve the candle problem, whereas only two of the eleven in the neutral mood group were able to do so.
Positive mood, in this and in other studies, increased creativity and flexibility in thinking. No one really understands how these changes in thinking are brought about. To some extent, positive mood may work simply because it is incompatible with anxiety and other negative emotions that hinder productive thought. But it is of course more complicated than that. Isen and her colleagues suggest that positive mood influences the way in which cognitive material is organized and retrieved from the memory, a sensible hypothesis that has yet to be adequately tested. Because positive mood is associated with increased dopamine levels in the brain, they also speculate that the increase may account for the facilitation of cognitive processing during elevated mood states. Surges in dopamine appear to draw attention to unexpected events or conditions, including those that predict reward; this, in turn, may make more likely the active pursuit, exploration, and understanding of the circumstances surrounding such events.
The effect of positive mood on thinking and behavior is by no means straightforward, nor is it consistent across studies. Scientists at Washington University in St. Louis found that college-age subjects in whom a positive mood had been evoked did better on verbal tasks but worse on visual ones. Subjects in whom an anxious mood had been generated, however, did precisely the opposite: they performed better on visual tasks and less well on verbal ones. Perhaps because the detection of physical danger is based largely on visual cues, it makes sense that anxiety and fear, which are highly primitive and instinctive emotions, focus and improve visual perception. Language, a far more recent addition to the brain’s repertoire, may be more obviously linked to younger systems in the brain that generate pleasure.
It is not obvious to what extent mental activation, and not just mood, is important in increasing cognitive fluency. Too-great activation may overwhelm and ultimately undermine originality and productivity. But some activation is crucial to attentiveness, motivation, and the capacity to translate thought into action. Intellectual and creative advantages prompted in a laboratory situation may not be important
in the real world, unless the individual is also physically alert and compelled to act.
Manic-depressive illness, because it is strongly heritable and often characterized by exuberance (as well as being related to a spectrum of exuberant temperaments), is a particularly important, naturally occurring psychological laboratory for looking at the effects of mental activation and euphoric and expansive mood states on thinking and behavior. Manic-depression, also known as bipolar disorder, is unique in its importance to understanding these effects. It is possible to see in mania and depression the impact of powerful mood changes on an individual and to compare in the same individual the effects of positive mood changes (for example, those of mild mania) with those that are negative (for example, those of depression).
Manic-depression is a well-studied illness that has been carefully observed and described since the time of Hippocrates, five hundred years before the birth of Christ. It is relatively common, occurring in its most severe forms in 1 percent of the population and, in its very mild and briefer variations, in at least another 5 percent. Bipolar illness encompasses a wide range of temperaments and psychopathologies. In the classic form of the disease, both mania and depression are severe, potentially life-threatening clinical conditions characterized by extreme changes in mood, thinking, energy levels, sleep patterns, and behavior. Mania—a state during which, as the composer Hugo Wolf put it, “the blood becomes changed into streams of fire”—is distinguished by an often wildly exuberant mood (albeit one joined by irritability and, not infrequently, depression), expansive and grandiose thinking, cascading speech, phenomenally high levels of energy, little need for sleep, a frenzied tendency to seek out others, terrible judgment, and rank impulsiveness. Mania, an inherently unstable state, is often accompanied by florid psychosis, that is, by delusions and hallucinations. Depression, in stark contrast, is characterized by a flat, irritable, and apathetic mood, sluggish and morbid thinking, profoundly disturbed sleep, reclusive behavior, and an almost unimaginable lethargy and mental pain. Psychic life is dull and colorless, and virtually every aspect of living is laborious. Depression conserves energy; mania expends it. If exuberance is the Champagne of moods, mania is its cocaine. Mania is exuberance gone amok.