Photo by  Joshua Davis  on  Unsplash

Just over a month ago, I was hiking through a mountain rainforest in Uganda in search of a wild gorilla family. Upon finding them, my knowledgeable guide’s first piece of advice before our careful approach toward the animals was simple: do not stare into their eyes.

The logic of this advice was straightforward in the context of the gorillas: they can perceive a stare-off as a threat. And of course, when a 350-pound silverback perceives a threat, the human on the receiving end is likely to be the significant underdog in any consequent fight.

I didn’t think much about it at the time, but in hindsight, the threatening nature of stares applies similarly to humans. I’ve witnessed fights erupt between angry men following a question along the lines of “what are you looking at?”, when one deems that the other has maintained eye contact for too long. And I can only imagine the tiresome frustration that many women experience from the overzealous and not-so-subtle sexualizing stares of certain men while walking down the street.

But why can a look have such a powerful effect? There’s no physical contact involved, so you might think it should be easy to ignore a stare, just as it’s easy to ignore someone’s cough or sneeze. We can think of the question “why?” in two parts.

The first part of the question is to ask what it means when a person stares into our eyes. It’s easy to understand why information is most important to us when it’s personally relevant. We can ignore a nearby conversation until somebody mentions our name, at which point we are suddenly all ears. Hand movements also don’t mean anything until we notice somebody pointing directly at us. Whenever others behave in a way that relates to our sense of identity, we desperately want to find out what is going on. What are they thinking about me? Why are they pointing at me? Why are they looking at me? Any thought or intention that the offending person harbors at that moment could be a sign of danger, and so we are built to pay attention and respond accordingly.

The second part of the question is the trickier one. What is the mechanism by which a look can exert its powerful effects? Even when we know it makes sense to ignore somebody looking at us on public transport, we can’t help but occasionally glance back to see if they’re still staring. A recent study out of Princeton University tackled exactly this question, and their results give new meaning to the phrase “shooting daggers”.

The researchers showed participants an image of a paper tube standing on a table and asked them to indicate the critical angle at which they thought the paper tube would succumb to gravity and fall over if tilted. Next to the tube was an image of a human character’s face, and its eyes could either be looking directly at the tube or be covered with a blindfold.

To understand whether participants treated the tube differently depending on whether someone stared at it, the researchers compared the tilt angle judgments for a tube falling toward the direction of the face and a tube falling away from the face. If participants felt any “push” coming from the eyes, then they would judge a tube to fall sooner when tilting away from the eyes, in line with the push.

Participants consistently estimated a smaller angle when the tube fell backwards away from the face; in other words, their estimates suggested the tube would fall more easily when tilted in the direction to which the character was looking. This difference did not exist when the face in the image was blindfolded. People attributed some sense of physical force to the visual gaze of the character in the picture, with an intensity equivalent to a light puff of air.

The experiment was set up in a way that made it difficult for participants to notice any patterns in their responses. So, without being aware of it, they were somehow intuitively and implicitly believing that staring directly at a falling paper tube would give it an extra push.

In a repeat experiment, the researchers replaced the blindfolded character images to see whether they could replicate the effect in different conditions. They instead used images with a non-blindfolded character who looked in entirely the opposite direction from the tube. Participants responded in the same way: a direct look at the tube was judged to project an invisible physical force toward it, and the force was absent when the character looked the other way.

In a final experiment, the researchers tried another interesting manipulation. Using exactly the same images, they told one group of participants that the character was looking directly at the tube, and told another group of participants that the character was actually looking past the tube at the wall on the opposite side of the table. They wanted to test whether participants were really attributing a force to the inferred focus of the eyes rather than, for example, just the direction of the head.

The first group of participants who knew that the eyes were focused on the tube responded in the same way as the participants in the previous experiments: they reported that it would take a smaller tilt for the tube to fall over backwards (away from the eyes) than forwards (toward the eyes) when that character was staring at the tube. But the second group of participants, who believed that the character was looking at the wall rather than the tube, showed no such effect. Looking at the wall was treated in the same way as being entirely blindfolded. The eyes could only exert their imaginary force on the tube when people believed that the character was gazing directly at it.

Participants were expressing an unconscious bias in their perceptions of how eyes work. When specifically questioned on their beliefs, only around 5% of people actually believed that the eyes could exert any direct physical force on an external object, and none of them were aware of how the character in the image was affecting their reactions to the tube tilt. And yet, their actual judgments during the experiment showed that they couldn’t help but feel an invisible force beaming out of the character’s eyes.

Photo by  Jared Rice  on  Unsplash

Photo by Jared Rice on Unsplash

The idea that beams are emitted from the eyes during vision, often referred to as “extramission”, has been historically and culturally pervasive, dating all the way back to Greek philosophers around 400 BCE. This primitive intuition may explain the physical eye-force that participants perceived during the experiments above, and it may more generally explain the overwhelming power and influence that we can sense from extended eye contact.

Gaze is particularly powerful because it is one of our most reliable social signals for inferring attention in other people. Even newborns are sensitive to the direction in which other people are looking, because we are born with an instinct to use gaze signals in understanding the world around us. When we talk to someone, and we notice their eyes shift and fixate on something behind us, we cannot help but turn around to check it out ourselves. We assume that whatever they are staring at must be worthy of our own attention too.

Context is of course all-important when it comes to eye contact. The same loving look from our romantic partner can appear predatory from a stranger. We might experience a physical beam from both of them, but one hits us with a feeling of love while the other hits us with a feeling of discomfort. But unless we’re associating with Superman or X-Men’s Cyclops, both beams are invented within our skulls.

Next time we notice an obnoxious person staring incessantly at us with no hint of polite subtlety, we can reflect on why their line of sight is causing us to feel frustrated. Even in a completely safe environment, a stranger’s eyes can act like a faint push in the chest. We feel an illusory physical force breaking into our personal space and we perceive it as a social violation. But when we expect no real harmful threat, we can try to rationalize our reactions rather than start a fight or make ourselves more angry than we need to be. No matter how physical their staring feels, it’s worth remembering an obvious but perhaps camouflaged fact: the look itself is making no direct contact with our body. As long as others keep their distance, there will always be only light and air between us.