You know that creepy feeling when you’re busy checking your phone or reading a book and suddenly you feel someone watching you? It makes the hairs on the back of your neck prick up, and you can’t help but turn around.
Where does it come from? Is it pure imagination, or is there something more fundamental at work here?
Turns out it’s an essential feature of the human brain.
This phenomenon is known as “gaze detection” or “gaze perception.” Studies have found that the brain cells that initiate this response are surprisingly precise. If someone turns their gaze off of you by turning just a few degrees to their left or right, that eerie feeling quickly fades.
Scientists theorize that there is a complex neural network behind gaze detection but it hasn’t been identified yet. That is, not in humans. A study with macaque monkeys discovered the neurological circuits responsible for their gaze detection, even getting down to the specific cells involved.
This specialized machinery in the brain reveals just how important your gaze is when communicating with others. Where you look conveys how you feel and what your intentions are, what you like and what you don’t like, and directs attention to meaningful things in the environment.
Furthermore, direct eye contact is perhaps the most powerful nonverbal signal we exchange with others.
It’s central to intimacy, intimidation, and social influence.
Think of a time when you were out in public somewhere and you could sense someone was staring at you, without you even having to look in that person’s direction. What information was your (peripheral) visual system using that led to this awareness?
The first things we usually notice are the other person’s head and body positions. If either is pointed in your direction, especially in an unnatural way, this is a big tipoff. The most obvious case is when someone’s body is pointed away from you, but their head is turned toward you. This then alerts you to pay closer attention to their eyes.
But even when head and body positions don’t give us much information, studies find that our peripheral vision can still detect another’s gaze remarkably well. How do we do this?
One factor goes back to our gaze detection system, which makes us more sensitive to the position of others’ eyes than we realize. Another thing we have to consider is how human eyes differ from the eyes of other animals.
What’s so unique about the anatomy of human eyes?
The biggest difference is that when looking at human eyes, it’s easy to distinguish the dark center (the pupil and iris) from the rest of the visible eyeball (the sclera, the white part). These are hard to distinguish in other animals: in many species, the pupil and iris cover most of the outward appearance of the eye, and also their sclera tends to be darker than the human one.
So humans have the greatest amount of visible white sclera. This contrast between the white sclera and the dark center makes it much easier to tell where someone is looking.
Having such an easily detectable gaze would be a liability for many species, especially predatory ones. As a predator, you don’t want others to know you’re staring at them, so a darker, less visible sclera is perfect.
Then what about when we feel someone staring from behind?
According to a 2013 study published in Current Biology, that’s just a failsafe. Humans are hardwired to think that someone is starting at us when we can’t see them, even if we have no evidence to suggest so.
Psychology Professor Colin Clifford of the University of Sydney’s Vision Centre found that when people can’t tell where a person is looking, they automatically assume they’re looking at them.
“A direct gaze can signal dominance or a threat, and if you perceive something as a threat, you would not want to miss it,” he said. “So simply assuming another person is looking at you may be the safest strategy.”
And that tingly sensation in the back of your neck? It’s purely psychosomatic in nature: it arises from the thought of being stared at, not the physical act itself.
Want to learn more? Here’s an interesting video:
What about you? Have you ever given any thought to this phenomenon?