I also think you are taking the worst version of my question. I'm not claiming they were dumb. Any more than I think my kids are dumb. But I have seen some o

I also think you are taking the worst version of my question. I'm not claiming they were dumb. Any more than I think my kids are dumb. But I have seen some of my kids and family where certain mental things "click" far faster than they do for others. To the point that I don't have much trouble claiming some of my family is more intelligent than others. Many of them more so than I am. Many less so, of course. To that general idea, I similarly have zero issue with claiming some dogs are dumber than other dogs. They obviously all fail at what we would call language skills, in they can form a rudimentary problem solving ability just fine. And, I can't remember what thread I said it in, but I do stress this isn't a transitive property. It is a lot like someone can be better at sports than someone else, but worse specifically at a specific sport.