For instance, complex forms of associative learning, like motivational tradeoffs.

So that's the ability to show that they sort of value some stimulus and they're able to sort of flexibly alter their behavior when they have different competing demands on them.

Because they're simple, because they have such tiny brains, the thinking has always been they couldn't possibly be sentient.

But of course, you know, we can return and say, well, actually, if we see a nematode doing all the things that are on our criteria, maybe we should just think that our preconceived intuitions about how simple an animal has to be before it's non-sentient are false.

Maybe it's just that evidence allows us to allow nematodes into the sentience club.

Heather, how could and should we face the issue of animals being kept, I mean, perhaps in quite large enclosures, but in environmental conditions that are a very, very long way from the conditions they evolved to live in?

Yeah, so I think one of the things that good zoos really need to be recognising now is the importance of choosing species that suit their site.

And so that means if you're a city zoo, choosing species that don't have particularly large space requirements.

If you're a countryside zoo, you can have these sort of big open range ungulates.

But I think that also includes climate factors.

If you're in a cold climate, don't keep tropical animals.

If you're in a warm climate...

Digging into education a little bit more then, what exactly is it that we need people to learn about the natural world? And what actually do they learn in zoos, Heather?