Nature, Nurture: Let’s Call The Whole Thing Off

How much freedom each person has to develop returns us to the issue of whether nature and nurture can be separated. Thinking of traits as being either environmentally or genetically caused cripples our understanding of human development. As Kagan puts it, “To ask what proportion of personality is genetic rather than environmental is like asking what proportion of a blizzard is due to cold temperature rather than humidity.”

A more accurate model is one in which chains of events split into further layers of possible paths. Let’s return to alcoholism. Drinking produces greater mood change for some people. Those who find alcohol to serve a strong palliative function will be more likely to use it to calm themselves. For example, if they are highly anxious, alcohol may tranquilize them. But even this tranquilizing effect, we should recognize, is strongly influenced by social learning.

Among drinkers who are potentially vulnerable to alcohol’s addictive effects, most will nonetheless find alternatives to drinking to deal with anxiety. Perhaps their social group disapproves of excessive drinking, or their own values strongly rule out drunkenness. Thus, although people who find that alcohol redresses their anxiety are more likely to drink addictively than others, they are not programmed to do so.

Mirror, Mirror

The goal of determining what portion of behavior is genetic and environmental will always elude us. Our personalities and destinies don’t evolve in this straightforward manner. Behavioral genetics actually shows us how the statistical plumbing of the human spirit has reached its limits. Claims that our genes cause our problems, our misbehavior, even our personalities are more a mirror of our culture’s attitudes than a window for human understanding and change.

How To Interpret Genetic Discoveries

1. Nature of the study

   Does the study involve humans or lab animals? If animals, additional factors will almost certainly affect the same aspect of human behavior. If humans, is the study a statistical exercise or an actual investigation of the genome? Statistical studies apportioning variation in behavior between genes and environment can’t tell us whether individual genes actually cause a trait.

2. Mechanism

   How exactly is the gene claimed to affect the proposed trait to which it is linked? That is, does the gene affect people in a way that leads logically to the behavior or trait in question? For example, to say that a gene makes some people welcome alcohol’s effects doesn’t explain why they would regularly drink until they become unconscious, destroying their lives along the way.

3. Representativeness

   Are the populations studied large and diverse, and does the same genetic result appear in different families and groups? Are those studied selected randomly? Early claims about manic-depression, schizophrenia, and alcoholism were made with limited groups and didn’t hold up. Findings about homosexuality will likely suffer a similar fate.

4. Consistency

   Are the results of the study consisitent with other studies? Have other studies found a similar genetic loading for the behavior? Have gene studies identified the same gene or area of the chromosome? If every positive study implicates a different section of DNA as the major determinant of the behavior, the likelihood is that none will hold up.

5. Predictive power

   How closely linked are gene and trait? One measure of power is the likelihood a syndrome or disease will appear given a genetic disposition. With Huntington’s gene, the disease may be inevitable. In other cases, only a small minority with a claimed genetic predisposition may express a trait. For example, accepting the original Blum-Noble figures for the A1 Allele, many more of those with the gene would not be alcoholic than would be.

6. Usefulness

   What use can be made of the proposed discovery? Simply warning people they will have a problem may be little help to them. Teenagers with an “alcoholism gene” who are told they are genetically predisposed to alcoholism may believe they cannot drink normally. Since most of them nonetheless will drink, they are then set up for a self-fulfilling prophecy in which they act as they have been told they would. If a proposed genetic discovery is not useful, it is merely a curiosity or, worse, a distraction from real solutions.

Richard DeGrandpre contributed to this article.

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    Last reviewed: By John M. Grohol, Psy.D. on 27 Aug 2007
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