alaskayorkie, I'm interested that you've managed to get not one but two dogs with therapy-quality temperament.
I'm starting to come to the conclusion that Thor is just a spooky dog. I definitely have high hopes for him improving, and he has come a long way -- but it took us a year to get to the point where I can have him Sit/Stay while I say, use an ATM. I still have to keep an eye out for strange people/dogs/other things that might bother him, because he will still break a stay if he spooks, and he spooks pretty easy.
I would have said that Shih Tzu's generally are known for being very calm, easy going dogs. Still, speaking with total honesty - do you think you are lucky, or very skilled/dedicated? I would love for Thor to get a Good Citizen award, but I've started giving up on that stuff because honestly, he seems like a really slow learner. Then again, it could be me.
(misc brag to end on a positive note: Thor will now play dead in front of other people! We spent a long time all our tricks in theory, because he didn't like performing in front of people. He really hammed it up today though.

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