What You Can Change . . . And What You Can't*: The Complete Guide to Successful Self-Improvement (8 page)

Antidepressants, like antipsychotics, have nasty side effects. The monoamine-oxidase (MAO) inhibitors, a once commonly used type of antidepressant, can be fatal. The tricyclics are milder, but they can produce cardiac problems, mania, confusion and memory loss, and extreme fatigue; a large minority of patients cannot tolerate them. The newest entry—Prozac—produces less drowsiness, dry mouth, and sweating than the older ones, but it produces more nausea, nervousness, and insomnia. Eli Lilly, its maker, may now be reaping the consequences of premature media hype, for there are case histories suggesting that Prozac causes unprecedented suicidal preoccupation. No controlled study has yet been done.
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Anxiety
. Anti-anxiety drugs relieve anxiety. They relax you dramatically and make life seem rosier. But like the antidepression and antipsychotic drugs, they are cosmetic. Once you stop taking them, anxiety returns in full force. Worse, when the anxiety stems from a real problem, you find you have done nothing in the meantime to surmount it. To the extent that anxiety is a message to do something about your life, anti-anxiety drugs prevent your getting the message. In addition, these drugs are overused in anxiety disorders: They are probably useless for panic disorder and for generalized anxiety disorder.
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Anti-anxiety drugs do not have the nasty side effects that the antipsychotics and antidepressants have. They probably won’t kill you, even in megadoses. But unlike the others, the antianxiety drugs become less potent the longer you take them, and they probably are addictive.
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Mania
. Lithium works well on mania. The main problem with lithium is that many manics refuse to take it because they like staying manic. In past centuries lithium had been used as a drug, but it was in disrepute (because it produced heart attacks) when John Cade, the Australian researcher, revived it by discovering its anti-manic property. Unlike the rest of the aforementioned drugs, lithium therefore generated few unpleasant surprises.
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The medical field was forewarned, and from the outset, patients who took lithium to relieve manic-depression were carefully monitored by their physicians.

Your Genes and Your Personality

The final principle of biological psychiatry is that personality is genetic. This is so contrary to the political sensibility of our times that its rediscovery is a shock to the system. How did biological psychiatry come to believe in such an “unenlightened” idea? Consider the fashionable explanation of child abuse.

Andy is a terrible two. Steven, his father, beats him whenever Andy throws a tantrum—not just a spanking: Black eyes and broken fingers
result. Once Steven starts, he can’t stop. Andy’s crying eggs his father on, and Steven doesn’t stop until Andy is whimpering quietly. All this came out when Andy’s mother took him, suffering from a “fall,” to the emergency room. Steven was arrested
.

Steven was mercilessly beaten by his own father through most of his childhood, and Steven remembers his father claiming to have been beaten by his own father when he was a boy
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Social scientists tell us that this cycle of child abuse is learned. Steven learned to beat Andy by being beaten by his father, and his father learned it the same way. It is quite possible that the children of abusers beat up their own children more often than do children who were not beaten up by their parents. But this evidence is equally compatible with another theory, one that is so unfashionable as to be omitted as a possibility by the social scientists who discovered the generational transmission of child abuse.
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What evolution works on
. The alternative explanation is that aggression is inherited, and that more aggressive people have “more aggressive genes.” People who beat little children are loaded with them, this theory suggests. If these little children are the abusers’ biological children, they will, in turn, grow up aggressive—not because they “learn” anything while being beaten, but because they inherit their parents’ aggressive tendencies.

Does Steven beat Andy because he inherited an aggressive disposition (which he has passed on to his doubly unfortunate son), or did he learn to beat up children from his own childhood beatings? How can this question be answered?

We are used to the idea of genes controlling simple characteristics like eye color. But can something complex, like a personality trait—aggression, for example—be inherited? To approach this question, it is useful to think about evolution: What does evolution work on and what gets selected?

I believe that genes, the particular molecular string of DNA, and simple traits like eye color are selected only
indirectly
. These get selected because their owner is more successful at reproducing and surviving than the owners of different strings of DNA. What gets directly selected, however, are the characteristics that cause their owner to outreproduce and outsurvive the competition. It is complex, “molar” traits like beauty, intelligence, and aggression that are the primary material of natural selection, which cares only about “modules,” the traits that lead directly to reproductive success. This means that complex trait selection is the normal mechanism of evolution.

Molecular biology has it backward. This field looks exclusively at simple traits and molecular building blocks (DNA strings), which can be measured—respectable, quantitative science. But this does not mean that nature is at all interested in simple traits or their molecular constituents, or that the inheritance of simple traits illuminates the inheritance of the more fundamental, complex traits.

Evolution, for example, has certainly worked on the complex trait of “beauty,”
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which is passed on from one generation to the next, as is the propensity to be attracted to it. Natural selection sees to it that attractive people have higher reproductive success than people less so. Beauty in turn is made up of traits like eye color, and eye color in turn has building blocks—for example, a particular chain of DNA. But beauty, like automobiles, comes in many models, and its definition changes within limits over time and culture. There are many ways to be attractive: many combinations of eye color, teeth, and hair. More important, a greater number of combinations will be ugly and will thus be eliminated from the gene pool. If there are myriad kinds of beauty, then there are myriad molecular ways to construct “beauty,” all of which get selected.

The upshot is that there is unlikely to be a molecular biology of beauty. There will not be “beauty genes,” or there will be so many combinations of genes underlying beauty as to be scientifically unwieldy. But beauty will still be subject to natural selection and will still be inherited. So too with intelligence, aggression, and all complex traits.
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It follows that the notion of “aggressive genes” may not make much sense, but that the notion of the heritability of aggression makes good, scientific sense.

How the inheritance off personality is studied
. Beauty, aggression, nervousness, depression, intelligence, and the ability to make up limericks all run in families. But if you can’t find the genes underlying a personality trait, how can you possibly find out if it is inherited rather than learned? This formidable question has a surprisingly simple answer: Study twins and study adopted children.

Identical twins are genetically identical. They always have, for instance, the same color eyes. Fraternal twins have, on average, half their genes in common. Sometimes one twin is green-eyed and the other blue-eyed. They are no more alike genetically than any other two siblings. When identical twins are more similar for some trait than fraternal twins, we say that the trait is
heritable
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This is true for eye color, but how about more complex traits, like limerick composing? Even if identical twins have the same limerick-composing ability (or its lack), and fraternal twins are not as similar, this talent could still be the result of child rearing. Everyone knows that identical twins are raised more similarly: Their parents dress them the same, they share the same bedroom more often, they take the same classes, and so on. Identical twins reared apart have the same genes, but they grow up in vastly different environments. If they are similar for some personality trait, it must be heritable and not learned. The study of identical twins reared apart is the best way to untangle the effects of child rearing from the effects of genetics.
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Indeed, if you want to attach a number for degree of heritability, simply take the correlation for identical twins reared apart: When that correlation is 1.00, the trait is completely determined genetically; when it is lower, say .50, this means that the trait is half genetic and half nongenetic in origin.

Identical twins reared apart
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Tony and Roger were given up for adoption as infants. Tony grew up in a warm and effusive working-class Italian home in Philadelphia. Roger was raised in Florida by austere, highly educated Jewish parents. While in his twenties, Tony, a traveling salesman, was eating at a restaurant in New Jersey when he was accosted by a very insistent woman diner. “Roger, how have you been? You haven’t called.” With effort, Tony was able to convince her that he wasn’t Roger and that he knew no such Roger. But he was intrigued and tracked Roger down. When they traded birth dates, each discovered he had a twin brother
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The similarity was spooky. Of course, they looked and sounded identical. But their IQ was also exactly the same. They used the same toothpaste. They had both been atheists since grade school. Their school grades had been the same. They both smoked Lucky Strikes and wore Canoe after-shave. They had the same politics. They had similar jobs and liked similar types of women. On their next birthday, they sent each other surprise gifts by mail: identical sweater-and-tie sets
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Over the last twelve years, a diligent group of University of Minnesota psychologists led by Tom Bouchard, David Lykken, and Auke Tellegen has studied the psychological profiles of twins. The group started with the “Jim” twins (both were named Jim), a pair whose reunion was written about in the press in the 1970s. The project snowballed. People who knew they had a long-lost twin came to the University of Minnesota for help in finding their twins. Minnesota has now accumulated no pairs of identical twins reared apart and 27 pairs of fraternal twins reared apart. Many of these twins’ very first reunions have taken place in the Minnesota laboratory. The stories of spooky similarity are repeated over and over (e.g., two identicals who each divorced a Linda to marry a Betty; another pair who named their sons James Allen and James Alan, respectively). Could it just be coincidence? Unlikely: These “coincidences” do not seem to occur in the lives of fraternal twins reared apart.

To scientists, the degree of heritability and the range of personality traits that are heritable are more impressive than the anecdotes. All of the following are strongly related in identical twins reared apart, and are much less related in fraternal twins reared apart:
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These findings have been duplicated in another massive study carried out with five hundred pairs of Swedish twins, identical and fraternal, reared apart and reared together, and now middle-aged.
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The results are similar, but you can add to the list:

• Optimism
  

• Pessimism
  

• Hostility
  

• Cynicism
  

Adopted children
. In addition to studying identical twins reared apart, there is a second way to separate the effects of genes from those of child rearing: by comparing adopted children to their biological parents versus comparing them to their adoptive parents. Hundreds of adoption studies have been done: Denmark keeps complete records of adoptions (and complete criminal records as well), so the Danish Population Register is a gold mine for untangling childrearing from biology. The criminal records (or their absence) for the fathers, both biological and adoptive, of all the adopted boys born in Copenhagen in 1953 and the criminal records of the sons have been scrutinized.

If neither the natural nor the adopted father had ever been convicted of a crime, 10.5 percent of the sons turned out to be criminals. If the adopted father was a criminal, but the natural father was not, 11.5 percent of the sons were criminals, an insignificant difference. So having a criminal rearing a child does not increase the child’s risk of himself becoming a criminal.