[Ronin]

All I know is that it has happened to me and it is spooky when it does.

It's a little itchy feeling right at the base of the neck and my immediate reaction is to whirl around and try to find who is staring at me. There is usually someone doing it.

I have heard that men who have been in combat have this "sense" to a much higher degree.

[unspun]

Interesting, thanks.