|MadSci Network: Neuroscience|
Thanks for your question. Let me say first that I'm not sure if all people do sense that they are being watched-I certainly don't, and I can't give a specific, scientific answer to your question. What I want to do is help you think about how people might feel that they are being watched and then look at how this could be.
First of all, let's think about how we perceive things with our senses. We see things because light enters our eyes and is captured by the retina, then processed in the brain. We hear because sound waves make our ear drums vibrate. We taste and smell because chemical molecules bind to receptors on our tongues and noses. We touch because we have sensitive nerve endings in our skin that respond to force. So in all cases, we have a physical source of energy (sound or light waves, molecules) which is captured by a sense organ and causes a signal to be sent to the brain, where infomation is processed.
Now, imagine someone is standing behind you and you cannot see, hear, smell or touch them, but you feel that they are watching you. How can this be? From what we said above, it would seem that they are transmitting a source of energy that you are intercepting and processing with your brain. But we don't know of any other way to sense things other than the ways that I described above. So we have 3 possibilities (1) there is a type of energy source and response that we don't know about, (2) you are aware of the person using means other than your senses (that is "extrasensory"-and again, we don't know how this could work) or (3) you are not really aware that you are being watched at all-you just think that you are!
I prefer the 3rd explanation, and I can think of a number of ways in which you might think that you were being watched. First, it's possible that the person watching you could be in the corner of your eye. We have quite a wide field of vision, a little more than 180 degrees and we are not always conscious of things towards the edge of our vision. But your brain could realise that someone at the edge of your vision was there, even if you don't see them directly.
Second, I think it's natural to feel that we are being watched. If you imagine our ancestors some millions of years ago when we were prey for various large animals, they were probably always looking around them in case they were about to be attacked. So you could argue that it's a good evolutionary adaptation to feel as though you are being watched, because it makes you more alert and able to escape more quickly when a threat really is there.
Third, I think a lot of the feeling that we are being watched is coincidence. If you are in a place with a lot of other people and you look up, it's quite likely that one of them will be looking in your direction. After all, you are looking in theirs!
Finally, I just wanted to say something about ESP, which you say "only some people have". There has been years and years of research into ESP and I'm afraid there is very little, if any, evidence that it exists. Some people seem to score a little higher than you might expect in tests such as predicting what card someone is looking at, but that's all the evidence there is and it's not very strong. It's not that scientists are close-minded to the possibility of such things, but the people who believe in them are just unable to prove their case, up to now at least!
I hope this helps with your question,
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