Dr. Eliza Middleton

Even from very early philosophy, like Descartes arguing that animals were just machines that mimic the appearance of experience, but they don't have any inner life.

That concept from the 1600s really shaped Western science and philosophy because they were very intertwined back then.

But even that machine metaphor, you know, that's been retreating in the face of evidence for 300 years.

We no longer look at a dog and think that a dog is a soulless, thoughtless being.

We might think it's only thinking about smelling butts and stuff, but it thinks.

The critical distinction is between nociception, which is our ability to detect a harmful stimulus, which is a reflexive, automatic response that requires no consciousness, and pain, which is that subjective experience of suffering, which requires the brain to generate a negative state.

And so with only nocioception, we react to touching a hot plate as a reflex.

You don't think about it.

You have sensed that it's hot and you move your hand.

With pain, we learn not to do that again.

Well, I think this really started back in 1991.

There's a paper from a group, Zabala and Gomez, and they were looking at whether crickets show any sort of pain-like responses to morphine.

Much like we are able to withstand more pain when we get treated with morphine, they develop tolerance to it, so they need progressively more morphine to deal with the pain.

When they're treated with naloxone, which is a chemical that's used to block opioids in humans, it showed the same impact in the crickets, that the morphine was no longer effective when they were treated with naloxone.

And it also showed that they get addicted to morphine, much like humans get addicted to morphine.

But then... In 2003, which is still a long time ago, researchers at Caltech identified a gene in fruit flies that they named painless because it was essential for thermal nocioception.

So flies lacking that gene failed to respond to damaging heat.

So they were able to, you know, turn that on and off and there we have some evidence of nocioception.

So that evidence in invertebrates and insects has been around for, you know, quite a while, I'd say.

But...