I think what James is talking about is; Capturing personality is one thing, but capturing the correct personality is another all together.

We might like to see a happy, bubbly mastiff, but what if there is nothing happy or bubbly about that dog in reality?

I capture the "wrong" personality quite often when doing rescue photos. I make the shrinking violet look outgoing and happy, I make the scared to death puppy look thrilled to be in front of the camera. My goal in this case, is to get folks to meet the dogs, then they can decide if the personality is a fit for them.

When doing portraits, I don't think it would serve us very well to capture a "personality" in the image that has nothing to do with a dog.

On the head cocking, I haven't met a dog yet that I couldn't get that out of if I tried hard enough, but then what's the point if that isn't a "normal" behavior?