Q&A – How Does Heredity Influence Behavior?

Question: What role does heredity play in influencing the behavior of a kid like mine?

Answer: Child development experts have argued for more than a century about the relative influence of heredity and environment, or what has been called the "nature-nurture" controversy. Now, at last, it may have been settled. Researchers at the University of Minnesota have spent many years identifying and studying one hundred sets of identical twins who were separated near the time of birth. They were raised in varying cultures, religions, and locations, and for a variety of reasons. Because each set of twins shared the same genetic structure, it was possible for the researchers to examine the impact of inheritance by comparing their similarities and their differences on many variables. From these and other studies, it became clear that much of personality, perhaps 70 percent or more, is inherited. Our genes influence such qualities as creativity, wisdom, loving-kindness, vigor, longevity, intelligence, and even the joy of living.

Consider the brothers known as the "Gem twins," who were separated until they were thirty-nine years old. Their similarities were astonishing. Both were married to women named Linda. Both had dogs named Toy. Both suffered from migraine headaches. Both chain-smoked. Both liked beer. Both drove Chevys, and both served as sheriff's deputies. They even shared a weird sense of humor. For example, both enjoyed faking sneezes in elevators to see how strangers would react. This degree of similarity in the personalities of identical twins raised separately speaks to the remarkable influence of inherited characteristics.

A person's genetic structure is thought to even influence the stability of his or her marriage. If an identical twin gets a divorce, the risk of the other also divorcing is 45 percent. However, if a fraternal twin divorces, sharing only half as many genes, the risk to the other is only 30 percent.

What do these findings mean? Are we mere puppets on a string, playing out a predetermined course without free will or personal choices? Of course not. Unlike birds and mammals that act according to instinct, humans are capable of rational thought and independent action. We don't act on every sexual urge, for example, despite our genetic underpinnings. What is clear is that heredity provides a nudge in a particular direction—a definite impulse or inclination—but one that can be brought under the control of our rational processes.

Obviously, these findings are of enormous significance to our understanding of children. Before you take the full credit or blame for the behavior of your sons, remember that you played an important part in the formative years—but by no means the only one.

As for your rebellious sixteen-year-old, I suggest you give him some time. He will probably settle down in his early twenties. The prayer is that he won't do something with long-term implications before he comes through adolescence.

By Dr. James Dobson