I'm having a problem with barking at night. I've tried to go out and calm her down, but it normally does not work. I'll see her looking as if she has spotted something, but I don't seen anything. So far my neighbors have not complained, but I'm sure it is just a matter of time. She does not do it all the time. It might happen 3 nights in a row and then she won't do it for a week or two. Any suggestions on how to calm her down?