I'm unsure that that was what our colleague Darkwind said. He said that his cat, and to a lesser extent his dog, do without training what some service animals are trained to do.
My understanding of "training," human or animal, is to take activity that is in an animal's behavioral repertoire ("comes naturally to them"), and to make that behavior more frequent, or occur more often in specific situations, or able to occur on "cue" (that is, when the human and the animal communicate so they can agree that now is a good time for that behavior).
DW's argument, as I understood it, stemmed from the indisputable fact that animals can be, and actually are, trained to perform alerting, This means that alterting is within animals' behavioral repertoire. It follows that some animals will exhibit the behavior spontaneously, without training.
Add to that the definition of alterting, and Darkwind reports that his cat and dog, to name two animals, do alerting spontaneously, without training. That they do so makes a positive contribution to the quality of DW's life. I sense in his words the hope that it makes a positive contribution to theirs as well.
As arguments go, Mr W, this one is starightforward. Or so it seemed to me anyway.
The nature of alerting behavior is to make an inference from evidence, and to find a way to get a crisp message about the conclusion to move across the interspecies barrier in timely fashion. These are cognitive feats of a high order. Training can help a lot with the second goal: human and animal might agree on a "signal." Training can't help at all, however, with the first goal unless the necessary inferential competence is already there in the first place.
It is all the more remarkable that DW's animals have concluded on their own initiative that all of that is worth their effort. There's no question that it is worthwhile for Darkwind. Apparently, then, the animals show interest in Darkwind's welfare, and reason about what is in his welfare. If that is also in their interest, then that doesn't diminish their inferential accomplishment in the least.
Somebody is home inside each of those two skulls. It's time to meet the neighbors, Mr W.