Don’t be so quick to swat fruit flies – you could hurt their feelings

Elephants mourn their dead, octopuses play catch, grey parrots recognise themselves in the mirror. But how about crabs that weigh up decisions, bees that play games and fruit flies that dream?

The past decade has seen rapid developments in the field of animal consciousness, upending widely held assumptions about which sorts of animals exhibit signs of consciousness.

The New York Declaration on Animal Consciousness, signed last week by 39 leading scientists and academics, aims to reframe the conversation, bringing surprising new species into the mix.

“Striking new results have hinted at surprisingly rich inner lives in a very wide range of other animals,” says the declaration, “including many invertebrates, driving renewed debate about animal consciousness.”

It asserts that as well as “strong scientific support for attributions of conscious experience to other mammals and birds”, there is also a “realistic possibility of consciousness in all vertebrates and many invertebrates”.

Finally, the Declaration says that “when there is a realistic possibility of conscious experience in an animal, it is irresponsible to ignore that possibility in decisions affecting that animal”.

The Declaration has been co-organised by Jonathan Birch, an associate professor in the department of philosophy at LSE and author of a book, The Edge of Sentience: Risk and Precaution in Humans, Other Animals, and AI, due to be released later this year. It follows the Cambridge Declaration on Consciousness in 2012, which recognised possible consciousness in cephalopods, birds and non-human mammals, and reflects a fast-changing field.

“We want to create a moment to get people to notice this emerging science of animal consciousness,” Birch says. “It’s a topic that has long been marginalised in science. It’s only in the last 10-15 years that there has been a broadening of the ambitions of consciousness science to also study the experience of other animals.

“The evidence has come in from a wide range of animals indeed that it’s not just mammals, or vertebrates like birds and reptiles and fish, but also invertebrates – octopuses, crabs, lobsters and insects. In evolutionary terms, the inferences get a little bit more tentative, and the evidence perhaps a little weaker, but we think even in insects there’s a realistic possibility of conscious experiences.”

For many laymen, the most persuasive example of non-mammal intelligence, whose remarkable behaviours have been made famous by many articles and documentaries, most notably the Oscar-winning film My Octopus Teacher, in which a South African filmmaker forms a friendship with a common octopus who plays with him, and shows remarkable ingenuity in learning to fight off sharks.

“During my training in the early 2000s, animal sentience and consciousness were treated like pink elephants, conspicuously ignored in serious scientific discourse,” says Dr Alexandra Schnell, a leading octopus researcher and documentary maker. “However, the burgeoning field of animal sentience has revitalised these topics, allowing discussions about subjective experiences in animals to flourish.” We now know octopuses can use tools, solve mazes and recognise human faces.

“Updating the declaration of consciousness to include more animals, such as cephalopods, is pivotal because it recognises their complex cognitive and emotional capacities, ensuring more ethical and informed treatment,” she adds.

“This acknowledgment can lead to better protection under animal welfare laws, more humane handling in research and food industries, and a broader understanding of consciousness across different species.”

They aren’t the only sea creatures surprising researchers. For Professor Bob Elwood, at Queen’s University Belfast, the starting point for his research was a chance encounter with the chef Rick Stein. When Elwood explained his specialism in animal welfare, Stein asked him if lobsters could feel pain.

“I’d studied crustaceans for a long time but it had never crossed my mind,” he recalls. “The opinion at the time was that they responded by a nociceptive reflex – we have those also – if you touch something hot you move your hand rapidly, before the message gets to the brain.

“The pain kicks in after you move your hand. These reflexes are important. If crustaceans simply responded by reflex there would be no worry about them feeling pain when you were boiling them or dismembering them alive.”

He decided that while he couldn’t prove they were feeling pain, in a human sense, he could try to find out if they were responding just by reflex. “I ran a whole series of experiments,” he says. “When I started, I was concerned about being thought odd by my peers at even considering the idea they might feel pain.”

His results were remarkable. He found that crabs will rapidly learn to avoid a dark shelter in which they receive electric shocks and use another which is safe, and they will do it in just two trials. Crayfish will do it within one trial.

“It’s really rapid and it’s not just a reflex.” In another experiment, he put caustic soda or acetic acid on prawn antennae. “They would rub the affected antenna against the side of the tank and rub it through their little claws,” he says. “And you could reduce it by applying a local anaesthetic.”

He also found that hermit crabs exhibit strong preferences for different kinds of shells.

“No one of these experiments is critical in suggesting consciousness or pain,” he says. “But when you see again and again, with different studies asking different questions, and they start agreeing, and you get evidence supporting the idea of pain, you cannot dismiss it.

“You have to take it into account. The more studies are done, the more likely it is that these animals experience pain. We now think they should be given the benefit of the doubt. They shouldn’t be boiled or torn up when they’re alive.”

Lars Chittka’s career has been a similar journey of discovery on the subject of bees. He is a professor at Queen Mary University in London and the author of The Mind of a Bee. “I really think we are witnessing a Copernican revolution in the understanding of animal minds,” he says, adding that his understanding of animal consciousness has changed “profoundly” in the years he has been studying them.

His earliest experiments found that bees could learn about a predation thread, which they did “just fine”. Even a day after simulated attacks, bees displayed false alarms, “rejecting flowers that were perfectly safe after inspecting them, as if they’d seen a ghost, a great [threat] conjured up from memory.”

Subsequent experiments have shown bees playing, responding in a non-reflex-like manner to painful stimuli, among other behaviours. “They can solve puzzles apparently by thinking rather than trial and error,” Chittka says, “they behave as if they can imagine objects, they take into account their own individual body dimensions when navigating obstacles, indicating a form of self-awareness, and can combine multiple memories ‘in their heads’ to calculate new information.

“For each of these findings, a critic might find an alternative ‘simple explanation’ but for all of them in combination this looks increasingly hard. The truth is that we have yet to find a single convincing piece of evidence that indicates the absence of consciousness.”

For Bruno van Swinderen, a professor at the University of Queensland, the humble fruit fly offers a way to examine the origins of consciousness mechanistically. “I am at the bottom of the pecking order of conscious animals,” he says. “You’ve got cats and dogs, dolphins and elephants. Even bees do interesting cognitive things. Then there’s fruit flies, which I work on. Why would they be included in this?

“But it’s worth trying to understand from the bottom up why consciousness may have evolved, why it is adaptive. If you understand it that way it makes more sense to study the fruit fly.

“With the fly we have the connectome [the map of neural connections in the brain], so we can completely understand how everything works. I think that bottom-up approach might be more productive than all the shenanigans that came from the top down. Humans have too much baggage, too many narratives, to try to really understand the problem.”

One thing Van Swinderen studies is selective attention, which is a fly selecting some stimuli and ignoring others.

“We look for neural correlates of that in the brain and see the fly is able to suppress one set of visual stimuli and select another one. That’s selective attention, which is a building block, potentially, of consciousness.”

His research has also shown that flies sleep, and lose consciousness at the same concentration of anaesthetic as a human.

“Why would a simple animal such as a fly need to have a stage of sleep where it is essentially awake but disconnected? And we think it’s our really valuable asset, that we lose consciousness, but something is lost in a fly at the same content. So it’s probably a similar mechanism.

“The conclusion I’ve come to is that it’s about prediction. Brains are prediction machines. They need to predict the future to move through the world and make models of the world about what might happen next.

“When you pay attention to something you pay attention because you have a model of it. Then one idea is you go into active sleep to optimise those functions, how you predict the world. These are theories of consciousness that can be studied, that don’t rely on difficult ideas like qualia [instances of subjective, conscious experience] or phenomenological consciousness. That’s why flies are useful.”

Part of the reason Van Swinderen has signed this declaration, and one of the reasons the field is enjoying such a surge of interest, is the discussion around the possibility of conscious artificial intelligence. “It’s a very opportune time,” he says.

“We’re seeing all these conversations about AI about when machines will get conscious. From a human perspective it’s hard to understand, but from a bottom-up perspective it’s easier to understand how consciousness might evolve from a simple circuit, like a fly brain circuit.

“It’s also an appropriate time historically. We had Copernicus and realised we’re not at the centre of the universe, then with Darwin we learnt there’s nothing unique about humans in terms of the special creation.

“Now it’s consciousness: maybe it is widespread among animals. That conversation that’s moving us away from being special is a useful societal discussion. A lot of the problems in humanity have spread from our special view of ourselves.”

If we are prepared to entertain the prospect of consciousness in a computer, we must be prepared to entertain it in fruit flies, too: a remarkable but chastening thought.