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Watch These Bears Mimic Each Other’s Facial Expressions

This week in science: sharing a womb with a twin brother could affect women's behavior, humans might be able to detect the Earth's magnetic field, and these bears do something we didn’t know bears could do.
Copyright Daniela Hartmann

Each week, we read what's going on the world of science and bring three of the wildest findings straight to you. Scroll through for the latest:

WATCH: These bears mimic each other’s faces while they play

As I binge-watched season 3 of Queer Eye this week, I often found myself grinning widely at my TV. Part of this has to do with the wholesomeness of the show, but perhaps another reason is something called facial mimicry: when we see facial behaviors in others, it can produce a similar facial behavior in response. It’s very common in smiling—when we see someone smile, we smile back. When it happens automatically, in less than one second, it’s called rapid facial mimicry.


It’s believed that we do this to form social bonds with each other and to share and synchronize our emotional states, says Derry Taylor, a PhD candidate in comparative psychology at the University of Portsmouth in England. “Emotional contagion is in turn thought to be an essential basis for empathy because empathy requires an understanding of others' emotional states,” he explains.

Generally, humans are thought to have a monopoly on higher cognitive states like empathy, but rapid facial mimicry can occur in other animals. It has been seen in creatures that are closely related to humans either evolutionarily, like gorillas and orangutans, or ones that are close to humans socially, like dogs.

In a new study published in Scientific Reports, Taylor and his colleagues observed rapid facial mimicry in a group of bears in the wild. (The were sun bears, the world’s smallest.) It’s the first time such exact facial mimicry has been seen outside of humans and non-human primates, a press release says.

The researchers observed the mimicry while the bears were playing with each other. They saw two different expressions: one where the bears displayed their upper incisor teeth, and one where they didn’t.

“Rapid facial mimicry occurred much more during gentle play compared to rough play,” Taylor says. “During play, the sun bears regularly transition between gentle and rough play. Therefore, it could be that rapid facial mimicry signals a readiness to transition into rougher play and thereby functions to regulate playful social interactions.”


Because rapid facial mimicry has been associated with empathy, it was thought to be something uniquely human, or human-adjacent. The new findings may lead us to expand our theories about which species use this type of communication and how. This “indicates that the building blocks of empathy might take their roots deep in our mammalian ancestry,” Taylor tells me. “I think this encourages us to think about non-human animals in a very different way.”

Credit: Derry Taylor, University of Portsmouth.

Humans might be able to sense the earth’s magnetic field, even if we’re not conscious of it

The earth has a magnetic field that animals can use for navigation—they can detect its intensity and direction across the surface of the earth and use it to go north or south during long-distance migrations, home to their nests, or finding breeding grounds. Their ability to detect the magnetic field is called magnetoreception, and the prevailing thought has been that humans, for whatever reason, don’t have this sense.

“This is mostly because we don't consciously perceive a magnetic field like we consciously see and hear things,” says Connie Wang, a graduate student in computation and neural systems at CalTech.

But in a new study in eNeuro, Wang and her colleagues wanted to see if people might have a brain response to a change in magnetic fields, even without conscious awareness of it.

They built a chamber they could apply magnetic fields in, and used EEG to record people’s electrical brain activity to those field changes. The magnetic field alterations they made were similar to nodding your head up and down, or turning your head right and left, Wang says—though the person in the experiment would be sitting still. They found that the brain does show some response to certain magnetic field changes after all.


“We saw a drop in amplitude of EEG alpha waves that dominate the brain signal when we are relaxing with our eyes closed,” Wang says. “This is a well-established response to other sensory stimuli (visual and auditory), so it indicates that the brain is picking up the magnetic stimulus and processing it.”

Were we perhaps once conscious of this ability, and have now lost it? Are we still using it? The topic needs further study, but Wang tells me that “humans, like other animals, might have once used magnetoreception for navigation when we lived as hunter-gatherers”.

She thinks it’s possible we still use it in everyday life without knowing, like when we encounter a fork in the road and decide where to go based on an urge or feeling.

“Some people seem to have a much better sense of direction or navigational skills than others,” she says. “We'll have to study human behaviors a lot more to answer these questions, but an ultimate goal is to train a magnetic sense into conscious awareness.”

Women with twin brothers make less money, have lower graduation rates, and are less likely to be married by their 30s

Fraternal twins develop from two different eggs fertilized by different sperm, which is how one twin can be a boy and another, a girl. (Identical twins are the result of a fertilized egg that splits in two.) In many ways, fraternal twins are just siblings born at the same time—though they do share the womb. While they develop together, they may be sharing something else: testosterone.


Boys begin to secrete testosterone early in gestation, and it influences how their bodies and brains develop. In a new study in PNAS, researchers found that when females with male twins grew up, there were associated life outcomes not seen in twins that were both girls. The authors hypothesized that these outcomes might be due to the female sibling being exposed to the male's testosterone in utero, though this current study doesn’t definitively prove causation.

The researchers found that, compared to female twins, females who developed with a male twin had around 15 percent lower high school graduation rates, 4 percent lower college completion rates, 12 percent lower likelihood of getting married by age 32, 6 percent fewer children by age 32, and 9 percent lower earnings at age 32.

Though each fraternal twin fetus develops in its own amniotic sac, it’s possible that testosterone from the male reached the female, says co-author Krzysztof Karbownik, an economist and research associate at Northwestern's Institute for Policy Research. It’s difficult to measure directly in humans, but Karbownik says there are two potential theories as to how: testosterone could diffuse from the male amniotic sac to female amniotic sac when the levels of testosterone increase at the sixth week of gestation. Or, the male twin might increase testosterone levels in the mother's blood and the hormone would reach female twin that way.


It could be that there are biological effects from direct exposure to male hormones during development, and that female twins gestating with a male co-twin have altered physiological and physical characteristics. But co-author and biological anthropologist at Northwestern University Christopher Kuzawa says that their best guess is that their findings were related to slight changes in behavior as a result of testosterone.

Exposure to testosterone might “nudge” a woman slightly away from gender-normative behaviors, inadvertently leading to the outcomes they saw. “Researchers have…documented correlationally that these females are more likely to engage in male-like behaviors, be more aggressive and competitive,” Kuzawa tells me. “To the extent that these gender non-conforming behaviors are socially not acceptable and penalized, it could generate the results we observe.”

There has been previous evidence that women with twin brothers might have altered behaviors indicative of in-utero testosterone exposure, Kuzawa says. But those studies were usually small, and they couldn’t rule out the fact that girl twins were usually raised alongside their brothers—so it wasn’t clear if any of those observations could be attributed to their upbringings instead.

The new paper uses a larger sample: all the births in Norway during a roughly ten-year period, from 1967 to 1978. They looked at 728,842 people total, and 13,800 twins. Because they had more twins to include, they limited their analyses to women whose twin brothers died soon after birth.


“Because these girls were not raised alongside a male co-twin, any differences in their schooling, wages, marriage, or other later outcomes, when compared to females whose female co-twin died soon after birth, are very likely due to being exposed to a male co-twin in utero,” Kuzawa says.

If this is the reason for their findings, it’s important to note that they might not apply to twin samples in different historical or cultural contexts, Kuzawa says—this kind of “nontraditional” behavior could be received in different ways now.

“Whether the impacts are negative, positive, or neutral, in terms of outcomes like graduation, employment, wages, and even family size, is likely strongly dependent upon the cultural norms of society at that time, and those norms can change rapidly, as many societies have experienced in recent decades,” he says.

Your weekly science and health reads

The fertility doctor’s secret. By Sarah Zhang in The Atlantic.
A fertility doctor that decided to use his own sperm to help his patients have kids.

Call me cozy. By Lena Dunham in The New York Times.
Sometimes coziness isn’t a luxury, but a necessity to cope with chronic pain.

We aren’t really in control so why worry about neurointerventions? By Hazem Zohny in Aeon.
Just a friendly reminder that we have very little control of anything, let alone our brains.

'Super-smeller' helps develop swab test for Parkinson's disease. By Ian Sample in The Guardian.
“Most people cannot detect the scent of Parkinson’s, but some who have a heightened sense of smell report a distinctive, musky odor on patients.” The super smeller in this story smelled the Parkinson’s in her husband 12 years before his diagnosis.

The only metric of success that really matters is the one we ignore. By Jenny Anderson in Quartz.
We’re all so focused on improving ourselves and our careers—what if those things will never offer us happiness?

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