Nature vs. Nurture: How Are Personalities Formed?

Is it Genetics or Environment and Experience That Make Us 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 things 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 had a clear winner. While we don't really know how much of our personality is determined by our DNA and how much by our life experience, we do know that both play a part.

The "Nature vs. Nurture" Debate

The use of the terms "nature" and "nurture" as convenient catch-phrases for the roles of heredity and environment in human development can be traced back to 13th-century France. In simplest terms, some scientists believe people behave as they do according to genetic predispositions or even "animal instincts," which is known as the "nature" theory of human behavior, while others believe 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" argument rages on as scientists debate how much of who we are is shaped by genetic factors and how much is a result of environmental factors.

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 by suggesting that abstract traits such as intelligence, personality, aggression, and sexual orientation can also be encoded in an individual's DNA. The search for "behavioral" genes is the source of constant dispute as some fear that genetic arguments will be used to excuse criminal acts or justify antisocial behavior.

Perhaps the most controversial topic up for debate is whether or not there's such a thing as a "gay gene." Some argue that if such genetic coding does indeed exist, that would mean genes play at least some role in our sexual orientation.

In an April 1998 LIFE magazine article titled, "Were You Born That Way?" author George Howe Colt claimed that "new studies show it's mostly in your genes." However, the issue was far from settled. Critics pointed out that the studies on which the author and like-minded theorists based their findings used insufficient data and too narrow a definition of same-sex orientation. Later research, based on a more conclusive study of a broader population sample reached different conclusions, including a 2018 groundbreaking study (the largest of its kind do date) co-conducted by the Broad Institute in Cambridge, Massachusetts, and Harvard Medical School in Boston that looked at the possible links of DNA and homosexual behavior.

This study determined that there were four genetic variables located on chromosomes seven, 11, 12, and 15, that do seem to have some correlation in same-sex attraction (two of these factors are specific only to males). However, in an October 2018 interview with Science, the study’s chief author, Andrea Ganna, denied the existence of a “gay gene” per se, explaining: “Rather, ‘nonheterosexuality’ is in part influenced by many tiny genetic effects.” Ganna went to say that researchers had yet to establish the correlation between the variants they’d identified and actual genes. “It’s an intriguing signal. We know almost nothing about the genetics of sexual behavior, so anywhere is a good place to start,” he admitted, however, the final takeaway was that the four genetic variants could not be relied on as predictors of sexual orientation.

The Nurture Theory: Environment

While not totally discounting that genetic tendency may exist, supporters of the nurture theory conclude that, ultimately, they don't matter. They believe our behavioral traits are defined solely by the environmental factors that affect our upbringing. Studies on infant and child temperament have revealed the most compelling arguments for the nurture theory.

American psychologist John Watson, a strong proponent of environmental learning, demonstrated that the acquisition of a phobia could be explained by classical conditioning. While at Johns Hopkins University, Watson conducted a series of experiments on a nine-month-old orphaned infant named Albert. Using methods similar to those employed by Russian physiologist Ivan Pavlov with dogs, Watson conditioned the baby to make certain associations based on paired stimuli. Every time the child was given a certain object, it was accompanied by a loud, frightening noise. Eventually, the child learned to associate the object with fear, whether the noise was present or not. The results of Watson's study were published in the February 1920 edition of the Journal of Experimental Psychology.

"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. Skinner eventually went on to prove that human behavior could be conditioned in much the same way as animals.

Nature vs. Nurture in Twins

If genetics didn't play a part in the development of our personalities, then it follows that fraternal twins reared under the same conditions would be alike regardless of differences in their genes. Studies show, however, that while fraternal twins do more closely resemble one another than non-twin siblings, they also exhibit striking similarities when reared apart from the twin sibling, much in the same way that identical twins raised separately often grow up with many (but not all) similar personality traits.

If the environment doesn'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 separately. However, while studies show that identical twins are never exactly alike, they are remarkably similar in most respects. That said, in "Happy Families: A Twin Study of Humour," a 2000 study published by faculty at the Twin Research and Genetic Epidemiology Unit at St. Thomas' Hospital in London, researchers concluded that a sense of humor is a learned trait influenced by family and cultural environment, rather than any genetic predetermination.

It's Not "Versus," It's "And"

So, is the way we behave ingrained before we're born, or does it develop over time in response to our experiences? Researchers on both 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 ultimately predetermine behavior. So, rather than being a case of "either/or," it's likely that whatever personality we develop is due to a combination of both nature and nurture.

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