I have noticed when I scratch a certain part of my dog's back, it makes him react like he has got an itch, but he doesn't really scratch at it, but more like strums at an air guitar:). I really hope you know what I mean here as I am not explaining myself very clearly. It is only on one particular place on his back, does anyone else's dog do this, what causes it and if so do you think that they like it or is it annoying, as he always looks like he is enjoying it and it is very funny to see!
one of my horses had a 'magic spot' and when I scratched it she went completely off her rocker and almost fell over - complete bliss!! Most animals have one, neck and shoulders are a favourite place, one of the dogs 'starts his motorbike' when he's scratched along his back. Bit like us really, yeas but that's nice, just a bit lower - yea there - ahhhhh - perfect.
I thought about this as one of my bitches went into overdrive when someone did it. Could it be a frisson of pleasure and associated with being mounted by another dog?. This could have lingered in both dogs and bitches.