There's an element of training in there.
I've been reminded of how I made friends with my mother-in-law's dog - an 8yro Cavalier King Charles Spaniel. I'm not afraid of dogs, but I won't have them doing what they like to me. She might have a favourite way to say 'Hello - Can I Be Your Friend?', but my response needs to be 'I Can Be Your Friend, But You're Never My Equal'. Without even realising I was doign it, I taught my mother-in-law's dog that I preferred to rub her belly in greeting, rather than have her jump up and lick my face. Within only a few weeks, she would roll over on her own accord as her way of greeting me.
So rollover submission can be taught. :-)
Wade.
