Do You Hug Left or Right?

You probably don’t remember, because hugs are (usually) performed without much worry about their logistics. But if you’re like most people, you hugged to the right, unless—unless!—you happened to have a very emotional embrace.

A new study published last week found that when people are emotional, some switch from the preferred right-side hug to the left, a phenomenon that can be explained by a quirk of our brains: they’re not symmetrical.

The brains is lateralized, which means its two sides, right and left, process information and produce actions in different ways. The most well known example of this is which hand you write with, or handedness. In most people, the right hand is dominant, which reflects how the left hemisphere of the brain is more specialized for fine motor movements. (Remember that the brain is contralateral, so what happens on the right side of the brain affects the left side of the body, and vice versa.)

“It’s not like your left hand can’t do anything,” says Gina Grimshaw, a cognitive neuroscientist at Victoria University of Wellington, who has studied hemispheric asymmetry for 25 years. “It’s not all or none, but some functions are sort of optimized to run better in one hemisphere or the other.”

When a person has a stroke on the left side of the brain, it often affects speech—but it won't if they have a stroke on the right side. The seat people choose in a movie theater will preferentially be on the right side, but when choosing a seat in a classroom it will more likely be on the left. This is in part because the brain anticipates different experiences in theaters vs. classrooms—ones that are optimally processed in different sides of the brain.

Past case reports have shown that people with brain damage to the right hemisphere had trouble identifying emotional faces, leading to a generalization that the brain processes emotions more in the right hemisphere. Researchers have found that in photos of academics on their university profile pages, there are significant differences in the direction English academics’ faces are turned, compared to science academics (English to the left, science to the right). This is because, the authors surmised, that “academics in the sciences would seek to pose as non-emotional rationalists and put their right cheek forward, while academics in the arts would express their emotionality and pose with the left cheek forward.”

A recent study found that when mothers hold their babies, they’re biased to do so on the left side, so that the emotional and social-processing of the right sides of their brain are more dominant in their interaction. A co-author of that study, Yegor Malashichev, says they’ve tracked similar left-leaning behaviors in a dozen other mammalian species too. “We have found that the infants follow the mother in such a way to keep her in the field of vision of the left eye,” he says. “We have further found that female animals like walruses and fruit bats keep their babies on the left arm as well as humans.”

One hypothesis, called the Right Hemisphere Hypothesis (RHH) says that all emotions are processed on the right side of brain, like the early brain damage cases suggested. But a competing theory called the Valence Hypothesis (VH) says that positive emotions are processed on the right, and negative emotions on the left, based on EEG studies that found this split in brain activity. Other guesses propose that emotions that involve approaching (happiness, love, anger) are processed on the right, while emotions that involve withdrawal (depression, fear) are processed on the right.

To address these theories directly, researchers have had to continually look for behaviors that are influenced by both positive and negative emotions, and see how they might change. What have they turned to now? The hug.

“The interesting thing about hugs is that they can be emotionally very different,” says cognitive neuroscientist Julian Packheiser, a co-author on the new hug study. “They can occur in so many different situations. For something like kisses, it’s theoretically conceivable to be in a very negative emotional state, but that’s rare to be honest.” Packheiser and his group observed more than 2,500 hugs at the departures and arrivals gates in a large German airport. They guessed that when a person was leaving, they were more likely to be feeling negative emotions, either from saying goodbye or from a fear of flying.

When people hugged as they arrived, the team guessed they were positive embraces, and they monitored the international arrivals to hopefully see people hugging who were coming from farther away, who had potentially been gone longer. They compared these hugs to YouTube videos of people blindfolding themselves in public, and being hugged by strangers walking by.

Overall, they found a strong preference for right-side hugs. When they compared hugs from the arrivals and departure gates, they didn’t find a difference. But, there was a significant difference between the emotional hugs at the airport and the neutral hugs. When people hugged strangers, they hugged to the right almost 92 percent of the time, compared to 83 percent of the time in the emotional hugs. What Packheiser says this implies, is that the right side of your brain—involved more in emotion—had a bigger influence in those emotional hugs, and was steering some people left, instead of right.

“Everybody thinks about how they feel as an individual person, but then, it turns out that a lot of people are actually doing the same thing, a lot more than chance would predict,” Sebastian Ocklenburg says, the senior author of the paper. “Your brain controls that, in a way. As long as you don’t actively intervene, it can happen.”

When they brought the experiment to the lab, they watched people hug mannequins after listening to short emotional stories. Again, they found that people usually hugged to the right, but that number was significantly less if people listened to an emotional story before their hug—whether it be happy or sad.

But emotions aren’t everything, as seen in the fact that more than 80 percent of the people they observed still hugged to the right, even at the arrivals or departure gates. Packheiser thinks there could be a couple explanations. First they had to assume the emotional states of the huggers they saw at the airport, and “there might have been a lot of neutral embraces at the airport and we just didn’t know about it," he says. Also, emotions are just one variable that control the way the body hugs. They found that if you’re right-handed or left-handed, that strongly influences the hug as well, and in most cases emotions were not enough to override this factor.

Still, Packheiser says that their hugging study offers evidence that the Right Hemisphere Hypothesis holds up, at least for hugging—any emotion, good or bad, was preferentially processed in the right side of the brain. But Ocklenburg says that most researchers now think that all the various theories could be true in some way. Some apply for some behaviors and others for different ones. “There might be specific circuits where it's more in just the right, but others are valence, or emotion specific," he says.

I ask this question to Gina Grimshaw, and we mull it over using the more emotionally loaded example of women holding their babies to the left side, so that their right hemispheres are more involved. Could holding a baby on the right side instead change the emotional experience of holding a baby?

Grimshaw says this hasn’t been studied, and so she can’t say for sure. “But if we were to step back and say, what would theory tell us, is that it’s always a two-way street,” she says. “There’s this idea of embodied cognition–that the actions of our body, or the grounding of our body in the world affects how we process things. I don’t actually know the answer, but I think theory would suggest that it could change emotional responses and somebody should do some version of an experiment on that.”

But of course that experiment would not be based on a single mother holding a baby to the right once, she says. Similarly, when I ask her what I should conclude when someone hugs me to the right if I went in for a hug on the left (as in: are they not as emotional as I am?) she says there’s no such thing as a “tell-tale hug.”

“This is a really interesting way to study brains in general," she says. "But you would not want to use this to make any inference about one person’s behavior. Any behavior at any given moment in time is hundreds of processes working together, some of which are just chance. And some of which will be things about asymmetries of somebody’s motor system that has nothing to do with their emotional state.”

The reason scientists study lateralization and behavior in large groups, like 2,500 people at the airport, is precisely because it’s too difficult to infer emotional states and behaviors from a single person. Any examination into mothers holding their babies on different sides would require tracking many mothers, over long periods of time.

If you wanted to track a friend's hugging direction over the next 100 hugs you get, and compare those embraces to hundreds of hugs they give other people—that might elicit some meaningful data about their emotions while hugging you. But it might be nicer to just hug it out, regardless of what side you do it on.

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