Most people have experienced that strange sensation of being watched at some point in their lives. It's that feeling of knowing someone is staring at you even though you can't see them behind you. It usually ends with you turning around - just to check - only to find you were right all along and there was, in fact, someone looking at the back of your head.
But why is it that we can sense when someone is looking at us? Researchers have suggested several different reasons over the years, ranging from extrasensory psychic abilities to brief episodes of unconsciousness and even automated behaviors in the brain. However, recent studies have suggested that the sensation may actually be due to another biological process that suggests the brain is hardwired to suspect that someone is looking at you even when there is little evidence to support it.
Even without having a deep understanding of biology, most people know that humans are pretty good at being able to tell where someone, or something, is looking. Whether it is another person or an animal, people can usually determine within just a few moments the direction, and even the subject, of a gaze. Interestingly, we can almost always tell when another living thing is looking directly at us.
While we are good at seeing where animals are looking, we are even better at determining the direction of another person’s gaze. This is because human beings have a larger amount of white space (or sclera) in their eyes compared to other animals. The contrast between the dark pupil and white sclera therefore gives people the ability to better tell where someone is looking at a glance. It also helps our peripheral vision to pick up clues from the surrounding area more easily.
This skill has evolved primarily because of the way that humans interact with one another. By nature, we are social creatures that depend on cooperation and friendship to survive. Therefore, being able to communicate almost instantly with non-verbal cues is a huge advantage in many interactions. Recognizing that someone is looking at you means you can immediately determine that they want your attention and even what their intention may be.
However, gaze perception also plays another important role as it can aid in the discovery of potential threats in the immediate environment. Attackers typically look directly at their targets, so being able to determine why, or how, someone is staring at you is important for avoiding danger. Anticipating acts of violence is essential to survival and as a result this trait has been passed down evolutionarily for generations.