Nature Versus Nurture: How Are Our Personalities Formed?

What Really Shapes Who We Are?

Woman With Child Lying in Grass

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You got your green eyes from your mother and your freckles from your father. But where did you get your thrill-seeking personality and talent for singing? Did you learn these from your parents or was it predetermined by your genes? While it's clear that physical characteristics are hereditary, the genetic waters get a bit murkier when it comes to an individual's behavior, intelligence, and personality. Ultimately, the old argument of nature versus nurture has never really been won. We do not yet know how much of what we are is determined by our DNA and how much by our life experience. But we do know that both play a part.

The 'Nature Versus Nurture' Debate

The use of the terms "nature" and "nurture" as a convenient catch-phrase for the roles of heredity and environment in human development can be traced back to 13th century France. Some scientists think that people behave as they do according to genetic predispositions or even "animal instincts." This is known as the "nature" theory of human behavior. Other scientists believe that people think and behave in certain ways because they are taught to do so. This is known as the "nurture" theory of human behavior.

Fast-growing understanding of the human genome has made it clear that both sides of the debate have merit. Nature endows us with inborn abilities and traits. Nurture takes these genetic tendencies and molds them as we learn and mature. End of story, right? Nope. The "nature vs. nurture" debate still rages on, as scientists fight over how much of who we are is shaped by genes vs. the environment.

The Nature Theory: Heredity

Scientists have known for years that traits such as eye color and hair color are determined by specific genes encoded in each human cell. The nature theory takes things a step further to say that more abstract traits such as intelligence, personality, aggression, and sexual orientation are also encoded in an individual's DNA.

The search for "behavioral" genes is the source of constant debate as some fear that genetic arguments might be used to excuse criminal acts or justify divorce.

The most debated issue about the nature theory is the existence of a "gay gene," pointing to a genetic component to sexual orientation. An April 1998 article in LIFE Magazine, "Were You Born That Way" by George Howe Colt, claimed that "new studies show it's mostly in your genes."

If genetics didn't play a part, then fraternal twins, reared under the same conditions, would be alike, regardless of differences in their genes. But, while studies show they do more closely resemble each other than do non-twin brothers and sisters, they also show these same striking similarities when reared apart, as in similar studies done with identical twins.

The Nurture Theory: Environment

While not discounting that genetic tendency may exist, supporters of the nurture theory believe they ultimately don't matter and that our behavioral traits originate only from the environmental factors of our upbringing. Studies on infant and child temperament have revealed the most crucial evidence for nurture theories.

American psychologist John Watson, best known for his controversial Little Albert experiments with a young orphan named Albert, demonstrated that the acquisition of a phobia could be explained by classical conditioning. A strong proponent of environmental learning, Watson said:

"Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I'll guarantee to take any one at random and train him to become any type of specialist I might select ... regardless of his talents, penchants, tendencies, abilities, vocations and race of his ancestors."

Harvard psychologist B. F. Skinner's early experiments produced pigeons that could dance, do figure eights, and play tennis. Today Skinner is known as the father of behavioral science. He eventually went on to prove that human behavior could be conditioned in much the same way as animals.

Happy Families: A Twin Study of Humour, a study published by faculty at the Twin Research and Genetic Epidemiology unit at St. Thomas' Hospital in London in 2000, suggests that a sense of humor is a learned trait, influenced by family and cultural environment, and not genetically determined.

If the environment didn't play a part in determining an individual's traits and behaviors, then identical twins should, theoretically, be the same in all respects, even if reared apart. But some studies show that they are never exactly alike, even though they are remarkably similar in most respects.

So, was the way we behave engrained in us before we were born? Or has it developed over time in response to our experiences? Researchers on all sides of the "nature versus nurture" debate agree that the link between a gene and behavior is not the same as cause and effect. While a gene may increase the likelihood that you'll behave in a particular way, it does not predetermine or cause behavior.