actually we should talk about whether how Town style is to say sentient or sensient oh man sentient sensient sensient according to the dictionary the American pronunciation is s but interestingly a lot of the researchers in this area are British or Australian sentian let's just go with the sentient yeah we didn't win the Revolutionary War just to start saying sentient right now octopuses is it octopi octopuses uh crabs and lobsters can feel pain and will recognized as a sentient after the UK left the European Union they decided they needed a new Animal Welfare Law and they ended up including not just vertebrates but also any seapod molusk and any decopod crustacean including crabs lobsters crayfish prawns and Squids so all the ones we boil alive this hasn't actually led to any specific regulations in the UK yet but it really made me wonder how do detect pain in animals that don't make faces and don't have voices and if we think that some animals are sensient but others aren't where do we draw the line if you're like me you were raised on Disney and Sir David Attenborough this is a catastrophe and you're probably thinking of course animals can feel things they're alive but we can see why this is a debate if we look at the old family tree so we're here with the other mammals we share an ancestor that lived around 200 million years ago in our line diverged from that of the reptiles and birds a bit earlier together we make up the tetrapods which left the ocean and split off from the fish lineage over 400 million years ago and then when you get to the invertebrates like octopus squid crabs and insects our common ancestor with them would have been a very primitive wormlike thing that lived more than half a billion years ago so their brains and ours developed completely independently we ended up with a neocortex that's the wrinkly outer layer of our brains it's an important part for our pain perception and it's Unique to mammals birds do have something similar so scientists seem to agree that at least mammals and birds are sensient but hold up can you define sensient really quick yeah so sence is the ability to have good and bad feelings hm or maybe maybe it's better to say cience is the ability to have good and bad experiences that your ability to label the experience is what makes you s it's your ability to have the experience I guess I'm having trouble sorting out a sub subjective experience when there is something it is to be like what is conscious so the question okay in humans pain feels like an inherent thing but at some point on that dimmer switch it's either off or on yeah I did a bad job explaining sence to Adam but in my defense pretty much everybody does a bad job at this because it remains one of the biggest mysteries in science so we'll just say for the purposes of this video that senscience and Consciousness can be used interchangeably and they refer to a state of basic awareness but we're talking about something more specific than just receiving sensory input all of these living things can sense their environment and respond to threats some robots can too but most people think it takes more than that for those electrical and chemical reactions to be experienced and produce feelings like pain you don't have to be intelligent to be sensient you just need to be [Music] aware and we don't really know how that awareness is generated we don't know how it's generated we don't know what it requires we just know it's like dark matter it's in its existence is inferred by the fact that we're all here like observing things and feeling things and being nervous that we came across poorly at a party and whatnot so if if we don't know what is generating this awareness how can we say that some species have this and some don't that that's the whole question of this story Adam I okay great I don't know I mean and and if you talk to any of these researchers or these philosophers who are who are trying to do this they would say we can't be sure we can't prove it but they still think it's worth doing mhm so how would you try to figure out if a crab or an octopus could feel pain you'd probably poke it to see what it does right well in this study researchers pinched the tip of an octopus on arm right here where the arrow is and over the next several seconds you can see how it withdrew and kind of curled up to get away they also tried dipping the arm in tap water which is harmful for octopuses and it withdrew even faster but the key detail here is that these arms are no longer attached to an octopus oh wow okay you tricked me uh yeah cuz I was imagining a Sad Little Octopus at the end of that arm but no this was just that word that I can't remember nois notion no susception right no susception is a warning system that detects harmful things with specialized nerve cells in our skin called no acceptors if the stimulus is strong enough these receptors can automatically tell the muscles to move away from the harmful thing that's the withdrawal reflex you've probably experienced this when you're not careful with your toaster and as you can imagine this is super useful for staying alive so you can find no susception across the Animal Kingdom so these are Escape reflexes from a crayfish a fruit fly larvae and a simple nematode worm in sensient animals that notive signal also travels to the parts of our brain that generate the experience of ouch I don't like that so in medical research they often just call these pain receptors but what the severed octopus arm shows is that no susception can produce a response in the absence of any awareness or pain and so for that reason we think the ability to respond isn't going to be enough enough perhaps what we're looking for is something like the flexibility of the response Heather Browning is one of the authors on the review paper that convinced the UK to include invertebrates in their Welfare Law if the goal is to distinguish reflex behaviors from a pain response what is the best way of going about doing that yeah I mean so obviously there's difficulties because no one really agrees on whether you have control for enough things um but I guess you the kinds of things that you're looking for is perhaps new situations that the animal has experienced before so that it hasn't developed sort of a simple reflex response or just where the responses that you're seeing are flexible and relatively complex one of the key studies cited in their review involved a very small octopus maybe 8 or 10 cm with its arms out and they were placed in this special tank that had been wallpapered with spots and Stripes so first they just wanted to see which side of the tank it preferred and this cool octopus tracking system logged the time it spent in each chamber then the researcher injected some of the octopuses in the arm with some acetic acid this is basically a diluted vinegar and she told me this might feel like getting lemon juice in a paper cut these injections were done under sedation but when the animal woke up it was placed back in whichever side of the tank it initially preferred and locked on that side for 20 minutes while the acid was in the arm then they were taken out and allowed to rest for 5 or 6 hours and then they repeated the preference test but now they changed their preference and spent less time in the chamber associated with the acid injection for comparison they had a control group that received a saltwater injection and those animals did not change their preference this very carefully designed study is the first evidence for pain experience in the octopus you know this study has not been replicated that I know of but these are very statistically significant differences so basically there was some sort of some aspect of the pain experience was being remembered that they they were like I associate this striped room with that horrible paper cut I had earlier and I don't want to be around that so we're like pretty far from reflex at this point what Browning's team did is they came up with eight criteria these are sort of tests for sensient based on anatomy and behavior and after reviewing all of the research they could find they said octopuses meet seven criteria and we need more research on the eth what we can hope to do is gather a body of evidence so we not just give any one test or any one indicator but you know a body of evidence across a whole different range of things that should raise the probability of the sentience explanation that should make that just the better explanation for what we're observing than the skeptical explanation would be crabs satisfied at least five criteria based on studies showing that they can learn to avoid an area where they received an electric shock and that they will hold an injured claw close to their body and guard it with their other Limb and as a result the report recommended that octopus crabs and their close relatives be regarded as sensient for the purposes of UK [Music] law okay but here's the unsatisfying reality of it all if you EES drop on the conversations between researchers in these fields you'll find that there's no consensus on whether these are good criteria for sents some have said that under this framework a simple nematode worm could qualify for protection because they're capable of some basic learning and flexibility and it's hard to imagine that they're sensient with just 300 neurons although who knows and then there are some who still want to set the bar much higher and they claim that a neocortex is required to feel pain the problem with that is evolution offers plenty of examples of similar functions arising in different ways so we process our vision with our neocortex but we know lots of invertebrates can definitely see senss could be like that and that's what we may be learning from the octopus you know if we are persuaded by the octopus and the case recensions in the octopus it dismisses this claim that you need a cortex to have Consciousness or senss and you know I think that raises a lot of possibilities totally yeah there's this one counter example that we know for sure or not for sure but there's strong evidence from this one cerebral cortex missing creature that it's experiencing pain in a way that that we can kind of appreciate yeah when I went to the aquarium recently the octopus seemed uncomfortable these crabs looked annoyed with each other I spent a long time watching a spiny Lobster just calmly clean itself it's easy to imagine that these animals are experiencing their lives but it's really hard to prove and if you want to get technical about it we can't prove that any animal or any human actually feels pain all we can do is ask them how they feel and it's just hard to figure out a way to pose that question to a shrimp in the meantime we use these animals every day in research labs and aquariums but mostly in restaurants and kitchens and there are only a handful of countries that regulate how the food industry treats invertebrates same goes for fish in the US it's mammals like cows and pigs that need to be stunned so that they're not awake when they're slaughtered and that's not because science proved that pigs are sensient they get the benefit of the doubt and while researchers will keep trying to understand the mechanisms of sension the UK has taken this small step to extend that benefit of the doubt to the other side of the family tree hey thank you for watching this video if you're new here howtown is a channel that investigates where facts come from it's something that Adam and I started on our own independently and to help keep it going we've set up a patreon page where we're providing bonus videos and conversations for supporters of this project this week we'll be talking about insect sentence so when it comes to insect pain there has been this idea for a long time that they just don't react to injuries in the way that we would would expect a sensient animal to but I recently received a video from a researcher that is challenging this idea and she was studying fumble Beats