Or maybe such [ET] probes are smarter than that but are still "dumb." Maybe they're as intelligent as a dog, still having some sort of instinctive reasoning, able to learn new tricks, but that is kept under control by strict training. Such a probe would have more leeway in responding yet still be limited. Who knows, maybe an alien probe has a built-in invisible fence to keep Rover concentrating on his mission, sniffing out new life-forms.
And in those cases when an UFO is observed moving erratically, flying in a crazy pattern, it could be the invisible fence has failed for the moment and that Rover wants to play.
(Via The Anomalist.)
Bruce Rux has some interesting things to add to this theme in his wonderfully out-there book "Architects of the Underworld."