@Therese:
The best description is that the dog that suffers from seperation anxiety isn't anxious about being left alone because it feels abandoned but is instead worried about his/her owners needing them.
I was refraining from responding about the book (YES, stop laughing, I do actually often refrain!)
But unless you have some psychic ability, such a spin is really a bit silly. The author ascribes things and imaginings that make no sense. MOST dogs with separation anxiety are fine if ANY human is there, or a familiar one. So this theory, much as we may want to spin it's all about US, makes no logical sense.
But the bottom line is, it's a waste of energy making up such thinking because it has nothing to do with the reality of the situation. It would be as logical for her to spend time saying that when we are gone they worry an alien will suck them out of the home. Actually, that would fit BETTER because then ANY human would prevent it and they wouldn't have to be anxious, which is usually the case. See my point? One wiser trainer suggested that separation anxiety is a genetic predisposition to fear of being without the pack leader. But the wise trainer said while it might serve a survival need to stay with the pack, he couldn't prove it and it didn't make any difference. The problem was overcoming it.
A pretty snarky but imho accurate evaulation of Jan Fennell:
http://www.kateconnick.com/library/fennelllistener.html
I just feel she is long on anecdotal evaluations, short on real insights and spends a lot of time with silliness (which I consider the almost psychic conclusion that your dog worries for your safety) instead of useful training help.
As with people, the cause of a phobia is rarely all that important. The important part is retraining the response. Often, as with people, it takes a very long time, working in small increments of time and expanding it to get a dog used to being alone. Sometimes it takes medications. Sometimes it requires other options (such as massively expensive steel crates the dog cannot hurt itself on or get out of, medications, day care, etc). But whether the dog has anxiety about being alone, about not having one of it's humans/pack leaders, or fear of aliens… the issue is the behaviors and responses.