I know dogs are capable of critical thought. I've seen it in action. Throw an object, watch the dog retrieve it. If there's another object nearby, you can often watch the dog go through a thought process to determine which object was the one you threw. Now, whether or not they have souls, that's another matter.
Funny thing, though. There is an older couple in our church who swear up and down that animals don't have souls because "God created man a little lower than the angels." We're his crowning achievement, so that settles it!
Sorry, that argument doesn't wash.
But then you have those others who swear up and down dogs have souls because they're affectionate. All that shows is that they can get excited about the way you smell before you shower. They have emotions, sensations, impulses. So do we. But the similarities end not too far off from there.
Do they have souls? I don't know. And I doubt that anyone else does either. If I was to err, I'd rather err on the side of telling my friend, who hopes they do, that, yes, she'll see her dog in heaven. What does it hurt to have that hope?
I don't know, either, but I like to think they do. Dogs having souls takes nothing from me. Having one does not attest to intelligence, rank or spirituality. It does not violate any known physical laws and it does not infer anything detrimental to belief in one's own soul. A dog having a soul does not compete with me having mine.
Maybe dogs' souls go to dog heaven; that bothers me not, and I do not understand why some people (who mostly have never had dogs) get frothing-at-the-mouth angry at the suggestion. Maybe they feel diminished by admitting animals have souls.
I think one big objection people have to accepting that animals could have souls is that, once accepted, then they could no longer, in good conscience, kill animals for food. No one will discuss that and bringing it up in conversation is guaranteed to end the peace of the moment. The reaction to asking, " would you kill a baby cow and eat it if you knew it had a soul that goes to animal heaven?" would be interesting. Not informative, but interesting.
My high school trigonometry teacher had a sign on the blackboard: "To each his own idea, however uninformed and incorrect it may be."
I always thought it clever because it included everyone.