Do men have a sixth sense?

Why is that the moment there is a sniff of a new man in your life, the ex seems to reappear on the scene? Several of my mates have said this, that if you're still friends with your ex, then don't talk to them for a little while, they immediately get in touch as soon as things start happening with another bloke, or potenially happening. Is there some kind of alert that goes off as soon as an ex girlfriend gets close to another bloke?