Dog Sentience--An Unanswered Question

I don't have a definition for sentience that isn't a very human one.

I think a lot about my dog Fargo, who is not the smartest dog we've ever had through her vet said I underestimate her. It's possible people don't become veterinarians to be impartial, which is fair enough, though she could be right. She's a subject matter expert and I am not.

Dogs are about as smart as two-year-olds per books written by humans, though it's unclear whether they are being tested by dog standards or human ones. Presumably the dogs can be tested against each other then compared to humans, which would be sort of like noting that there are entire breeds of dogs all of whom can outrun Usain Bolt.

I am not a child-haver but our friends who had us over during the pandemic expressed that comparisons could be made. We would show up at their house with a big bag of stuff and the dog, spend a lot of time keeping the dog out of trouble and take turns when she needed extra attention. She's older now and can be left at home on her own.

That all of this invites anthropomorphism, which I guess isn't totally a bad thing. When I read a classic novel, I try very hard to hold both that it is a product of its time but also that humanity doesn't get better if we don't hold ourselves to ever-improving standards. Similarly, I can view Fargo through my eyes and try to figure out what the world might look like through hers, with her head two feet off the ground, her minimally focused vision and her ability to smell me from all the way across the house. That is a gross sentence to me, but I assume not to her.

When I'm upstairs writing, she likes to sit, hip to hip with me. I'm assuming this is guarding behavior though the literal only threat there has ever been as the threat of vet care in an entirely different environment.