Further to all the other brilliant replies...
Sometimes I think they can anticipate OUR anxiety. They can pick-up on stuff that we don't even know we're feeling ourselves.
Here's a 'for instance'. We took Harry on holiday a couple of months ago. Andy and I were in holiday mode - Harry slept or looked out of the window all the way there, and all the way home

4 hours each way, no problem whatsoever.
Now, a couple of weeks ago, I drove Andy to an aerodrome about an hour away. I wasn't sure of the route - and I was
very anxious about Andy going up in a helicopter over London....Harry grizzled and mizzled and cried and fiddled about all the way there

He was a nightmare! Yet on the way home, he was back to his 'normal' self.
MY anxiety had gone, and it didn't really matter if we got lost on the way back, as there was no appointment to keep. Just wondering if those thoughts might help?!

Sally + Harry x