TUCSON, Ariz. — Ever wonder why some people are “huggers,” and others aren’t so into contact with others? It turns out biology may be behind that, at least for women. Researchers from the University of Arizona say that genes are a major deciding factor regarding how affectionate women are. They didn’t find the same relationship among men, however.
Affection levels among nearly 500 sets of twins were analyzed by researchers, in an effort to ascertain how much loving behavior is a result of genetics versus one’s environment. For women, they note that genetics can account for about 45% of affectionate behavior. Environment decides the remaining 55%, they believe. “Environment” in this case refers to the media, prior relationships, and other unique life experiences.
Conversely, genetics don’t seem to influence affectionate behavior among men. Even the study’s authors were surprised to see that men’s affection levels appear to be 100% determined by their environment.
“The question that drove the study was: Recognizing that some people are more affectionate than others, what accounts for that variation, and is any part of that variation genetic?” says study leader and UA professor Kory Floyd in a release.
“In my field, there is a really strong underlying assumption that whenever we see differences in a trait level in people’s social behaviors – like how talkative they are or how shy they are or how affectionate they are – those differences are learned; they’re a function of the environment,” Floyd explains. “A study like this makes room for us to talk about the possibility that a number of social and behavioral traits that we automatically assume are learned may also have a genetic component.”
How affection differs among twins
For this research, 464 pairs of adult twins were studied. The twins varied greatly in age (18-84 years old), and about half were fraternal, with the other half being identical. Twins are often used for “nature versus nurture” studies because, though usually raised in the same household and exposed to the same experiences in adolescence, only identical twins share the exact same genetics. In comparison, from a genetic perspective, fraternal twins are about as similar as any other pair of siblings.
Each participating twin rated how strongly they agreed with a series of statements about affectionate behavior. Then, responses among pairs of twins were compared to one another.
Now, if genetics don’t influence affection at all, that would mean that both fraternal and identical twins would have largely the same answers. That’s not what happened, at least regarding female twin pairs. Identical female twins gave much more identical answers than fraternal female twins. This is a strong piece of evidence that at least some aspect of affection is determined via genetics among women.
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Why is affection a genetic trait for women and not men? Floyd and his team don’t have a concrete answer to that question yet. But they did note that men are generally less affectionate than women.
“When we measure people’s tendency to be affectionate and to receive affection from other people, almost without exception we find that women score higher than men,” Floyd comments. “The trait of being affectionate may be more adaptive for women in an evolutionary sense. There is some speculation that affectionate behavior is more health supportive for women than it is for men, and that it helps women to manage the effects of stress more than it does for men. That may be partly why women are more likely than men to inherit the tendency to behave that way rather than that tendency simply being a product of their environment.”
Environment vs. genetics
Interestingly, researchers note that environments twins share, such as a childhood home or their socioeconomic background, seems to have little effect on affection. Instead, factors like a person’s friends and social interactions have a larger influence.
“It’s not exactly what we would expect, but for many behaviors and personality characteristics – including how affectionate you are – what twins do and experience differently in their lives plays a much bigger role than anything they experience together,” Floyd says.
The authors made it a priority to emphasize that their findings apply on a population, not individual, level. This means that not every woman’s affection is determined 55% by environment and 45% by genetics. It’s also quite possible for a person to be more or less affectionate than what their genes may predispose them toward. Nothing is written in stone.
“Our genes simply predispose us to certain kinds of behaviors; that doesn’t automatically mean we’re going to engage in those behaviors,” Floyd concludes. “And it certainly doesn’t mean that we have no control over them.”
The study is published in Communication Monographs.