Your sixth sense may be related to a gene

Walking and dancing. Typing on a keyboard or climbing Mount Everest. You use your “sixth sense” — your body’s uncanny ability to sense where it is in space — to perform everything from normal activities to great feats of athleticism.

Scientists have known about this ability, called proprioception, for more than a century, but they weren’t sure how it worked. You might think dancers or athletes would hold the answer, but it was researchers studying a rare genetic disorder who have shined a light on it.

The researchers studied a young girl and a woman who completely lacked this sixth sense. Their unusual set of symptoms included an extreme lack of coordination, difficulty walking, and a lack of sensation when objects were pressed against their skin. They both also have an unusual curvature of the spine, as well as feet, hips and fingers that bend at unusual angles. The results of their study were published in the New England Journal of Medicine.

The researchers learned that both patients didn’t start walking until they were between 6-7 years old and they both had problems learning to feed and dress themselves. Neither patient was able to walk with their eyes closed; they could only take steps if they could see their limbs as they moved.

Genetic analysis revealed a genetic mutation in a gene called PIEZO2, which has been associated with the body’s sense of touch.

One of the researchers, study co-author Alexander Chesler from the National Center for Complementary and Integrative Health, had been studying PIEZO2 in mice for years. But he’d never found a good way to study the gene in people — until now.

Trying to understand proprioception just by experimenting with mice was like trying to understand Beethoven by reading sheet music, Chesler told NPR. “But when I talked to the patients, it was like going to the symphony,” he said.

When researchers began studying these two patients, they were able to demonstrate that the PIEZO2 gene was responsible for proprioception, as well as sensations of touch. They learned much of what it was able to do by studying what the patients were not able to do.

In experiments, the patients were unable to walk blindfolded. They also weren’t able to move a finger from their nose to a targeted point if they were blindfolded. When researchers moved a particular limb for them, if they couldn’t see, they were unable to tell which way the limb was being moved. Once the blindfolds were removed, the patients were able to walk, touch the target and see the direction of their moving limbs.

There’s one other potentially interesting thing researchers may be able to learn from this new discovery: understanding if variations of the PIEZO2 gene contribute to whether a person is klutzy or coordinated.

“Could a finely tuned PIEZO2 gene contribute to superior athletic performance, or a poorly tuned one to clumsiness?” co-author pediatric neurologist Carsten Bönnemann of the National institute of Neurological Disorders and Stroke told Science. “I think it’s not impossible.”

Why can we sense when people are looking at us?

If you’ve ever felt like someone was watching you, you may have attributed that awareness to a sense of unease or a prickling on the back of your neck. But there’s nothing psychic about it; your brain was simply picking up on cues. In fact, your brain is wired to inform you that someone is looking at you — even when they’re not.

“Far from being ESP, the perception originates from a system in the brain that’s devoted to detecting where others are looking,” writes social psychologist Ilan Shrira. This concept may sound confusing, but it actually makes a lot of sense when you think about it as a survival instinct.

Many mammals can tell when another animal is looking at them, but the human “gaze-detection system” is particularly good at doing this from a distance. We’re able to easily discern where someone is looking.

This system is especially sensitive when someone is looking at you directly, and studies have found that particular cells fire when this happens.

“Gaze perception — the ability to tell what someone is looking at — is a social cue people often take for granted,” Colin Clifford, a psychologist at the University of Sydney’s Vision Center, told the Daily Mail. “Judging whether others are looking at us may come naturally, but it’s actually not that simple as our brains have to do a lot of work behind the scenes.”

When you catch someone looking at you, what is it that clued you in? Often, it’s as simple as the position of the person’s head or body.

If both the head and body are turned toward you, it’s clear where the person’s attention is focused. It’s even more obvious when the person’s body is pointed away from you but their head is facing you. When this happens, you immediately look to the person’s eyes to see where they’re looking.
Human eyes are different from those of other animals in this regard. Our pupils and irises are darker from the white part of the eyeball known as the sclera, and this contrast is why you can tell when someone’s looking at you or simply looking past you.

Other species have less visible sclera, which is advantageous for predators that don’t want their prey to know where they’re looking. However, human survival is more dependent on communication, which is why we evolved to have larger, white sclera, which help us make eye contact.

But when head and body positions don’t provide much information, research shows that we can still detect another person’s gaze extraordinarily well because of our peripheral vision.

We evolved to be this sensitive to gaze to survive. Why? Because every look someone throws your way is a potential threat.

Clifford tested this by asking study participants to indicate where various faces were looking. He found that when people couldn’t determine the direction of a gaze — because of dark conditions or the faces were wearing sunglasses — people typically thought they were being watched.

He concluded that in situations where we’re not certain where a person is looking, our brain informs us that we’re being watched — just in case there’s a potential interaction.

“A direct gaze can signal dominance or a threat, and if you perceive something as a threat, you would not want to miss it,” Clifford said. “So simply assuming another person is looking at you may be the safest strategy.”

credit: Laura Moss