I would be a little kinder to the researchers than that: crows and other animals understanding the concept of none is interesting and plausibly true. My quibbl

I would be a little kinder to the researchers than that: crows and other animals understanding the concept of none is interesting and plausibly true. My quibble is conflating this with zero, which is a much more powerful and advanced concept. Greeks, Romans, early medieval Europeans, none of them had the concept of zero, and they suffered for it. And what you've said about Koko the gorilla is true as far as I understand it. It was a media stunt, more Clever Hans than Mister Ed. It would be pretty cool if it wasn't, but I'd have to see some replication and I don't expect to.