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.
The human brain is structured to observe patterns in everything. It is the reason why people see faces in clouds and shadows that aren't there. It also explains why the brain sometimes makes assumptions about things with very little evidence. For instance, if your peripheral vision picks up on people standing in certain positions or moving in particular ways near you, your brain will quickly predict that those people might just be looking at you based on previous experiences where they were – provoking the sensation of being watched and tempting you to check.
It also explains why people often feel as though someone is watching them more intensely in dark environments. Here, the brain has even less data to work with, so it decides to err on the side of caution and is more likely to raise false alarms simply due to a lack of information.
Our brains are essentially hardwired to believe that we are being watched even when there is little evidence to back it up. This automatic gearing of our sensory organ ensures that we are constantly on guard against potential threats and ready to engage in any possible social interaction.
Some researchers also suggest that the sensation of being watched may be a way of drawing attention to ourselves. If a person looks over their shoulder after sensing that someone may be staring at them, they are likely to draw the gaze of those around them and in turn become more memorable. This could even provide a way of stimulating interaction.
The belief that we can tell when someone else is staring at us comes from the brain simply guessing. And thanks to our handy confirmation bias, humans only tend to remember experiences that reinforce their worldview. So, if a person senses someone is watching them and they turn around to find they are in fact correct, then they are much more likely to recall that event than if they had been wrong. After this happens a few dozen times, people actually start to believe they can detect another person’s gaze even when there is really no evidence to support such an ability.