This is a fascinating article and I’m not casting shade but more of a curious question: If humans are the ones that generally associate this sound with that thing, knowing dogs are very observant of us, how do we know the dogs aren’t just copying what we are unknowingly exhibiting toward them throughout their entire lives? I have no idea how you’d pull that out of the stats though. Maybe you could find languages that have different sounds for round and spiky and compare dogs from those households to English speaking households (or rather languages with k’s for spiky and b’s for round)