> We're also really good at fooling *ourselves*, both unintentionally and intentionally. So I think there'd be a big subset of the population that'd totally go in for the robodogs way before they were "perfect" anyway, either because they were fooled enough by them to accept them as loving pets, or because they *wanted* to be fooled by them.

This is an excellent point and one I can concede. We *are* really good at fooling ourselves, sometimes on purpose. Possibly we've come at this question -- "can robodogs replace real dogs?" -- from different angles. I'm arguing whether they can replace dogs in general, such that there would no longer be a demand for real dogs. But I'd definitely concede that they'd suffice in some cases, and maybe we only disagree about how many cases.

Anyway, here's what I fall back to. Have you thought about how REALLY good we are at recognizing human faces? There isn't a lot of variation in human faces, especially if you only consider the two sexes separately. And yet we recognize faces instantly. Even when we can't place them, they often strike an immediate chord of recognition. For me, this is particularly revealing with regard to the faces of actresses, because the phenomenon holds despite that we only see their faces in 2D and also despite that they're made up to look "perfect" (less distinguishing features). I've seen Scarlett Johansson a grand total of like 4 hours of my life, but when I see her picture, I instantly know it's her. Why? I have no idea. What features does my subconscious identify that allows me to place her so instantaneously? No idea whatsoever. But the smallest adjustment to the size of a cheekbone, the slant of an eyelid, the curve of a lip, and we'd pick up on it somehow, by misidentifying who the face belonged to or just thinking the person looked sick or pale or aged or just different somehow.

I saw a picture of a guy that famously looked like Ted Danson. He was just some guy somewhere that happened to look a lot like him, and I forget whether I saw his picture online somewhere, or if they showed his picture on a late night talk show or something, but in any case, I saw the guy's picture, and INSTANTLY, two things registered to me: (1) Whoa, this guy looks like Ted Danson, and (2) This guy isn't Ted Danson.

The human mind is amazing enough in its ability to register thought #1, but I'm at a total loss for how or why #2 came to me. I didn't know what looked different enough from the actual Ted Danson that I was able to identify that that wasn't him and was just someone that looked a lot like him, but in a split second my mind was able to interpret the image in front of my eyes and figure all that out.

Of course face recognition is a skill some people are better at than others. But there are other ways we recognize each other, another being voice recognition. If memory serves, you're not actually very good at face recognition, but you have a spectacular sense of voice recognition. A really big one that we're less conscious of is the manner of our body movement. People walk differently, gesture differently, and we pick all that up, knowingly or not. Here's a wild one: we have a great sense of *height* recognition. I saw an interview with a retired agent of some kind, FBI maybe, and he was saying that the best way to disappear into a crowd if people are chasing you is to walk on your toes or stoop down just a little bit. Because apparently the first criterion our brains use to pick someone out of a crowd is height -- and the difference of just two inches or so can be enough for our brains to subconsciously filter someone out as a possibility.

Now, obviously this is people, not dogs, and it's talking about *individual* people, not people as a biological species. The point is just that our brains are SO tuned to recognizing things like ourselves. Would I be able to identify trees or airplanes or mountains with as much precision? Not even close. But dogs have our most fundamental biological traits in common with us. They're anatomically analogous, they're emotional in the purest ways we also are, they're expressive, and they're personable. Try to simulate all that in a robot, and I think those amazing parts of our brains that discern one voice from another, one face from another, one walk from another, would start screaming at us that something is off.

The illusion would more likely hold for people unfamiliar with dogs in the first place, and -- as you say -- people willing to fool themselves. But I still say most people will be better at recognizing differences than our robotics engineers will ever be at eliminating them.