Since Professors David Lykken and Auke Tellegen, both from the University of Minnesota, published Happiness is a Stochastic Phenomenon in the May 1996 edition of Psychological Science, they and their work have generated a remarkable amount of national and international media attention. Their work is based on demographic and questionnaire data gathered from a large sample of adults drawn from the birth-record-based registry of middle-aged twins born in Minnesota from 1936 to 1955, the Minnesota Twins Registry. Lykken and Tellegen's article on happiness is a well-wrought but small piece of a body of research based on samples drawn from the Minnesota Twins Registry.

In the article below, "The Heritability of Happiness," Professor David Lykken reflects on the implications of his research for individuals and society as a whole.

The Heritability of Happiness

David T. Lykken, Professor of Psychology

University of Minnesota

(This article is published in the Harvard Mental Health Letter)

Better is a handful of quietness,
Than both the hands full of labour
And striving after wind.
Ecclesiastes 4:6

When T. J. Bouchard, Jr. and colleagues, at the University of Minnesota, measured the systolic blood pressure (BP) of 56 pairs of monozygotic twins who were separated in infancy and reared apart (MZA twins), we found a within-pair similarity, measured by the intraclass correlation, of .64. If we neglect the intrauterine and neonatal environments, then the only likely cause for this cotwin resemblance in adult BP is the twins' genetic identity. Therefore, we can say that the heritability of BP is about .64, which means that about 64% of the variation in these single BP readings is associated with genetic variation between the twin pairs.

But every physician knows that BP changes from time to time depending upon health status, emotional arousal, recent activity, and a variety of other factors. If the genes determine anything about BP, surely it is the basal BP, the characteristic set-point to which an individual's BP returns after perturbation, not the momentary level measured at some arbitrary time. To get an estimate of the heritability of the BP set-point we should make repeated measurements and then compute the MZA correlation of the average BP values. If this increases the correlation to .85 (let us say) this would mean that the heritability of the BP set-point is about 85%.

Happiness or subjective well-being (SWB), like BP, also varies from time to time about an average value that is characteristic of the individual. My colleague, Auke Tellegen, and I have measured SWB on hundreds of pairs of middle-aged twins, both MZs and dizygotic (DZ) twins reared together and also on Bouchard's twins reared apart. In addition, we have obtained estimates of average SWB by repeating these measurements after intervals ranging from 4 to 10 years. The heritability of single assessments of SWB is about 50% while the heritability of the set-point or mean happiness level is about 80%. What these data seem to indicate is that about half the variance in one's momentary feelings of SWB is determined by the great genetic lottery that occurs at conception (which determines 80% of individual differences in the set-points) and the other half depends on fortune's favors, good or bad.

Psychologists David Myers, at Hope College, and Ed and Carol Diener at the University of Illinois have been studying SWB for years with remarkable results. They find first that SWB is essentially unrelated to socioeconomic status, to income, to level of education, to gender or to race. We have replicated all but the race findings (fewer than 2% of births in Minnesota are to minority parents so that our twin samples are almost exclusively Caucasian). Those who ride to work in overalls and on the bus are just as happy on average as those in suits and ties who drive in their Mercedes. Although men still have a tenuous hold on the reins of power, women's average SWB is at least as high as men's (this is especially surprising since we know that clinical depression is far more prevalent in women).

Second, to explain these curious results, the Illinois researchers have shown that the effects on current SWB of both positive and negative life events are largely gone after just 3 months and undetectable after 6 months. A happiness reading on a victim of a spinal injury---or on a winner in the lottery---taken a year after the event, is likely to give about the same value obtained before the event. Most people, within 6 months or so, will have adapted back to their genetically-determined set-point. Getting that promotion, having Miss or Mr. Right say "Yes", even having a "born again" religious conversion---each of these may send the happiness meter right off the scale for a while but, in a few months, it will drift back to the set-point that is normal for that individual. (Perhaps this is why evangelicals have annual "revival" meetings---to revive their faith and also their feelings of subjective well-being.)

One further replicated finding is that most people's happiness set-point is above zero, that is, on the happy side of neutral. Nearly 87% of some 2,300 middle-aged twins in our sample rated themselves to be in the upper third in over-all, long-term contentment. It seems plausible to suppose that, over the millennia of human evolution, those ancients who were grouchy or sad did less well in the struggle for survival and had less luck in the mating game. Our species has become biased toward positive well-being by natural selection.

Many interesting questions remain to be answered. It seems probable, for example, that people differ genetically in the amplitude of their time-to-time variation about their happiness set-points; this is Hippocrates' notion that some of us are naturally phlegmatic (think of former football coach Bud Grant or tenor Placido Domingo) while others are more labile and easily aroused (think of another former coach, John Madden or another tenor, Luciano Pavarotti). That emotional lability, too, is genetically influenced could be tested by repeatedly assessing our middle-aged twins, say, weekly for a year. If the MZ twins correlated in the variability of their scores at least twice as strongly as the DZ twins (who share, on average, just half their polymorphic genes), that would confirm this supposition.

Cyclothymic individuals, and certainly the more extreme cyclothymes with bipolar affective disorder, seem to have variable set-points. Is this the same neurochemical mechanism that determines SWB differences among people in general or is normal-range emotionality different in kind from the instability that leads to mania and clinical depression? Moreover, this concept of a happiness "set-point" itself needs further clarification: are we talking about just an average of repeated measurements or is there a true homeostatic process that is activated by any deviation from the value characteristic of the individual?

Meanwhile, however, there are important implications of the findings already in hand. Much of the angst and debate generated by Herrnstein's and Murray's The Bell Curve stemmed from the apparent unfairness of their demonstration that successful people have higher IQs on average than do less successful people and that individual differences in IQ are determined largely by genetic differences. The scientific support for these conclusions is unequivocal and strong. By more nearly equalizing opportunities and improving social mobility, we have created a meritocracy in which those with greater talent and drive rise to the top while those with less drift downwards. Yet it seems to be intolerable to some that one's social status, often achieved by years of effort, is determined by attributes that are governed in part by one's genetic blueprint which was present from birth.

Now, however, we can factor in the finding that happiness is virtually uncorrelated with income or socioeconomic status. One can predict a person's SWB far more accurately from his identical cotwin's score even ten years earlier than from that person's income, professional status, or social position today. Those favored genetically by high IQs are indeed more likely to become doctors, lawyers, or chieftains of industry than are those destined to be plumbers or garbage collectors---but those clever ones are not likely to end up any happier.

My wife and I have always enjoyed watching the crew who swing by each Wednesday morning to collect our garbage. Those young men do their job with skill and athleticism and they seem always to be enjoying themselves. They are doing an essential job and doing it with style; why shouldn't they feel good about it? And I always get a lift from visiting my local plumbing supplies store. There one finds several men, all master plumbers, on one side of the long counter, making jokes and solving problems for the customers, either plumbers themselves or duffers like myself, on the other. The cashier at the end of the counter is as skilled and quick at her job as they are at theirs and I firmly believe that the average levels of amour propre, savoir-faire, and joie de vivre (the French seem to understand these matters best) at Park Plumbing Supply are higher than in many Wall Street boardrooms. Not all plumbing shops are as cheerful and well-run as this one and not all garbage collectors are as high-spirited as the crew who work my neighborhood but the data indicate that people in these lower status jobs have the same range of SWB set-points as do captains of industry. The people in my examples either have above-average set-points or they transcend their set-points by doing their jobs with skill and good humor---or, most probably, both.

The well-known Peter Principle, that people tend to rise to the level of their incompetence, would be less universally valid if more of us would recognize and act upon these happiness findings. How many skilled and happy school teachers have accepted promotion to principal only to discover a decline in their job satisfaction? A good news reporter may not make a good editor, a skilled actor might bomb as a director, a successful salesman might fail as sales manager. What if they all knew that the lure of higher pay and status is chimerical and that their SWB will bounce along above their personal set-points most reliably if they stay in the jobs that they do best? This is not to say that it is wrong or fruitless to aspire to and work toward high and distant goals, as long as one realizes that getting there---that is, the striving and the quotidian sense of accomplishment---really is at least "half the fun." If the goal is reached at last, a new one will have to be set in six months or so when the joy of the achievement will have largely faded. If the goal is not reached, then one must be able to say that the effort was itself worthwhile. Some Olympic athletes can see it that way when they fail to win a medal but many, I fear, cannot, especially those vulnerable young gymnasts and swimmers who have been acting out their parents' dreams rather than their own.

There is another lesson here also for parents. A former professor at my university, an expert on the assessment of high intellectual ability, had a son whose only interest was cars and engines. That father might have pushed and prodded his son through college into some unfulfilling white-collar career. Wisely, instead, he let his son study auto mechanics and helped him to establish his own garage which the university faculty patronized enthusiastically because the young man did such good work.

The interest shown by the media in this research has been unprecedented, suggesting that indeed the pursuit of happiness intrigues journalists as much as it interests psychologists. Our study has been written up in Science, Nature Genetics, and Science News, in the London Times and Daily Mail, in the Manchester Guardian, in the New York Times, Newsweek, and the many papers served by the Associated Press, as well as periodicals in Italy, Germany, and South America. Radio stations have solicited interviews, including the BBC in London, Edinburgh, and Belfast, plus others in Chicago, Los Angeles, and New York. All this has led me to speculate more freely about these findings than I might otherwise have done and a call from a San Francisco station suggested the following idea which, even on mature reflection, seems to me to worth further study.

The male homosexual whom I knew best, a cousin of my wife's, was someone who brought new life and joy to any room he entered. He was funny, he livened up any gathering, he was a delightful and imaginative host, an ideal guest, and a boon companion. His special qualities were wonderfully captured by actor William Hurt in the film, Kiss of the Spider Woman. Hurt plays a gay man, in some South American prison on a minor morals charge, who is celled with a political prisoner with whom Hurt's character, predictably, falls at once in love. This very macho cellmate is at first repelled by Hurt's effeminate ways but the Hurt character tells such interesting stories, produces a dinner party out of meager materials, and generally creates a light, fantastical atmosphere that mitigates the boredom and foreboding of imprisonment.

The actor Harvey Fierstein exemplifies the same qualities; only the intractably homophobic would fail to get a lift when he enters the room. What I am suggesting is that many gay men, at least those with more feminine natures, seem to make an art of daily living, they enliven the tedious, decorate the drab, make the mundane more amusing. These are all behaviors designed to keep one's SWB up above one's innate set-point. Perhaps this is a feminine trait---the single item on the Strong Vocational Interest Inventory that best distinguishes women from men is: "Decorating a room with flowers." Our Minnesota female twins in fact described themselves as somewhat happier on average than the males. Perhaps the euphemism "gay" is more apt than I had previously thought.

Stephen Bertman, a professor of classics at the University of Windsor, has shared with me an essay from which I borrowed the epigraph above. King Solomon, said to be the author of Ecclesiastes, concluded in old age that "there is no other good in life but to be happy while one lives. Indeed, every man who eats, drinks, and enjoys happiness in his work---that is the gift of God." Cicero discovered "the pleasures of agriculture, in which I find incredible delight" and Diocletian came to realize that being Emperor of Rome could not compare to the satisfactions of raising vegetables with his own hands. Voltaire's Candide and his companions, after many disappointments, discovered the same thing: "we must cultivate our garden." Perhaps because of its endless variety and annual renewal, gardening was both a solace and delight to the ancients as it is to many still today, a source of SWB that does not wear out.

But it is interesting that, like gardening, most of the things that can be counted on to give us a welcome, if transitory, lift above our individual happiness set-points are active rather than passive, and usually also constructive---activities that have a useful product. My personal set-point happens to be very close to the population mean (at least the Minnesota mean, which may be somewhat above average) yet I manage to bounce along above my set-point much of the time by growing vegetables, baking (I have mastered the perfect lemon meringue pie), fixing things around the house, and writing papers. And this effectance motivation is not merely cultural, the Protestant work ethic, for example. Our species is the only one to have the capacities for language, for developing a conscience, and for the enjoyment of making things.

Like language, however, these other two propensities require to be elicited, encouraged, and shaped by the parents, else a child may grow up an inarticulate, conscienceless, couch-potato. Worse yet, since breakage and destruction is the primitive manifestation of effectance motivation, seen in many youngsters, parental malfeasance can and often does produce a guiltless vandal and delinquent. Nurturing the child's innate pro-social proclivities, which include the inclination toward constructive endeavor, constitutes the most important responsibility of parents, the socialization of their offspring. The children of parents who fail in this responsibility grow up to be misfits, unskilled and poorly educated, rejected by their peers, economically dependent and often criminal---deprived of their birthright to life, liberty and the pursuit of happiness.

It appears that fathers have especially important roles to play in the socialization of children. We know for example that 70% of delinquents currently in custody in the U. S. were reared without the participation of their biological fathers. Young men thus deprived, whether they are black or white, are seven times more likely to end up in prison than those growing up with both biological parents. The proportion of young men aged 15 to 25 (the group at highest risk for violent crime) who were raised without fathers has more than trebled in the U.S. since 1973 due to accelerating rates of illegitimacy and divorce. Contemplating what this portends for our collective future is not a happy-making activity---unless we think constructively. The recent book, Licensing Parents, by Jack Westman, MD, is a good place to start.