system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can I feel when someone is staring at me?
gpt
You can't.

1. Confirmation bias causes you to remember the instances where you "felt someone staring at you" and then saw someone looking at you, and causes you to forget instances where the feeling didn't correlate to someone staring (and you'd be completely unaware of instances where staring did not result in the feeling of being looked at).

2. Suddenly looking around to catch the starer will catch people's attention, causing them to look at you.  You can then misinterpret their glance as meaning that they were staring at you before you looked up, when in reality they're staring *because* you looked up.

3. If someone walks up behind you, you can often hear a change in the acoustic properties of the room.