Insect consciousness: the minds of flies and psyche of bees

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The insect world is abuzz with life, but is there anything on their minds? Follow Amalyah Hart into a world of intricate research designed to explore the complexities of insect consciousness.

Dinis Gökaydin plucks a vial from the counter and holds it up to the light. Inside, a female fruit fly (Drosophila melanogaster) is crawling up its glass sides towards the false promise of freedom. Fruit flies do this when trapped – they travel upwards, buoyed by an instinct that tells them sky means salvation.

“It’s a bad morning because I’m feeling shaky for some reason,” Gökaydin says. Nervous energy punctuates the air.

What follows is one of the most precise and nerve-wracking pieces of practical science I’ve ever seen. First, he places Drosophila’s tube into a small opening in a metal block on the bench in front of us. The inside of this block is 2°C which, after three minutes, immobilises the fly.

Next, Gökaydin opens the vial and teases the fly out with a tiny instrument. He dabs some glue on the back of her body, and fastens her to a small metal plate, not much larger than a sim card. She’s ready for the final, macabre insult.

Peering down a microscope, Gökaydin uses another instrument to peel open the back of her head, into which his supervisor Bruno van Swinderen, will embed an electrode. I breathe a sigh of relief – he’s managed to achieve all this without killing her, a crucial part of the plan.

Gökaydin and van Swinderen, a professor at the University of Queensland’s Queensland Brain Institute (QBI), study how fruit fly brains function in different states – awake, asleep, or anaesthetised. They hope their work may throw up clues to an enduring scientific mystery – how, and when, did consciousness evolve?

A short history of consciousness

Seventeenth century philosopher René Descartes believed that consciousness was a uniquely human trait. Animals, he argued, made no effort to communicate their experiences. Plus, they lacked the ability to reason. He therefore believed that, while animals might cry or run from pain, they had no thoughts or sensations – their behaviour was pure reflex.

This view became culturally widespread and, just a few decades ago, any attempt to investigate animal consciousness scientifically would have been derided.

In 1974, American philosopher Thomas Nagel published a provocative essay titled What is it like to be a bat?, which parsed out the problem of creature consciousness. Unlike Descartes, Nagel believed consciousness was widespread in the animal kingdom, but impossible to understand. To be conscious is a completely subjective experience, while science is governed by objective inquiry, Nagel argued.

Bats were the perfect poster-child for this quandary: like us, they navigate the physical world but unlike us, they do so through echolocation. Biohacking notwithstanding, humans will probably never know how it feels to navigate the world through ricochets of sound.

Nagel had a point. The hunt for consciousness in the animal kingdom is hamstrung by the fact that no one can agree on what exactly consciousness is, or how it got here, let alone how to prove it’s there.

Scientists remain divided on whether consciousness is a profound but accidental by-product of cognitive evolution, or a central driver of our species’ evolutionary success. Some think it emerged as early as the invertebrates of the Cambrian explosion, more than 500 million years ago, while others think it appeared much later, in mammals and birds.

Numerous studies identify brain regions that may be involved, but there, too, disagreement reigns: is it housed in the front or the back of the brain? Is it in the neocortex, which only mammals have, or the brainstem, a region we share with most animals on Earth? And is consciousness tied to just one brain region, or made through the combined efforts of different neural circuits, thrumming together as one?

To make matters worse, there is no universally agreed upon definition of consciousness. Some researchers refer to ‘consciousness’, while others call it ‘sentience’, which refers specifically to the ability to feel and sense.

Other theorists divide it into ‘cognitive consciousness’, the ability to process information and solve problems, and ‘phenomenal consciousness’, which describes the capacity to have a subjective experience – to feel pain, see the colour red, taste the sweet flesh of a peach. Many scientists believe that subjective experience – this trait that, for us, gives life its richness – is not present in all animals.

Despite this lack of consensus, theories of consciousness are already pushing the needle on policy decisions. In 2022, the UK government moved to protect all vertebrates and some invertebrates, such as lobsters, crabs, and octopuses, under its updated Animal Welfare (Sentience) Act 2022. That change was fuelled by a growing body of research that suggests these creatures may experience pain.

In 2009, Robert Elwood, a professor at Queen’s University, Belfast, exposed hermit crabs to a series of electric shocks of gradually increasing intensity. Hermit crabs demonstrate clear preferences for certain species of shells, and Elwood wanted to understand how pain might influence their choices.

Crabs in higher quality shells would suffer higher-intensity shocks than those living in lower-grade shells before they finally, reluctantly evacuated. What’s more, when exposed to the shocks, crabs behaved in ways that looked achingly like true pain. Some crabs made escape bids, desperately trying to scale the walls of their tanks, while others furiously groomed the place on their body where the shock was administered.

“That’s exactly the sort of profile of behaviour we would expect to see if crabs had a state that does for them the sort of thing pain does for us,” says Dr Jonathan Birch, a professor of philosophy at the London School of Economics (LSE), who was asked to review the evidence by the UK Government ahead of the 2022 change to the Act.

“Admittedly this is an area where there’s a huge amount of uncertainty,” adds Birch, who heads the Foundations of Animal Sentience (ASENT) project at LSE. “But I think the evidence is pushing us to take seriously a realistic possibility of conscious experience being extremely widespread.”

The oddball paradigm

The fly is suspended in front of an LED screen, which is divided in half. Every few seconds, a panel of light will appear on either side. The light has an equal probability of appearing on the left or right side each time – a computer generates the patterns at random. Meanwhile, the electrode in Drosophila’s brain is registering her reaction to each flash – unusual patterns create pulses of electrical activity in her brain.

Gökaydin and van Swinderen investigate attention, sleep, and memory in fruit flies, and van Swinderen has been probing fruit fly brains for the better part of two decades. About a decade ago, van Swinderen set about designing a system that could monitor Drosophila brains while they slept. He found that in fruit flies, as in humans, sleep consists of both active and quiet phases. In humans, our active phase of sleep is known as REM sleep – the kingdom of dreams. Van Swinderen’s data forced him to take seriously the possibility that fruit flies, too, may dream.

But today’s experiment requires this fly to be wide awake. It’s based on a psychological concept called the ‘oddball paradigm’. When the brain encounters a novel stimulus – an ‘oddball’ – it experiences a spike in activity as it attempts to understand what’s going on, and assess for threat. That spike is connected to the feeling of surprise; in humans, surprise is a jolt that funnels our awareness to the stimulus. But surprise is also costly.

“If you have a trillion synapses in your brain, even if you increase the synaptic release by one per cent, you’re looking at a tremendous amount of extra energy requirements,” van Swinderen says.

So, brains need to optimise their function while minimising wasted energy: “One way to do that is to be predictive, rather than reactive”.

Van Swinderen believes consciousness is an evolutionary adaptation that helps animals make predictions about the world around them, by focusing attention on difficult problems.

“I would really be of the opinion that consciousness is adaptive,” he says. “If you had a simple animal that, within its very limited environment, was making 100% perfect predictions, it wouldn’t need it.”

Van Swinderen and Gökaydin aren’t the only ones interested in fruit fly cognition and behaviour. Another 2021 Drosophila experiment, from a US-based team of researchers, found that chronic social isolation interrupted fruit flies’ sleep cycles, and led them to overfeed – a phenomenon linked to loneliness in humans.

It’s important to note that data that hints at loneliness, or dream-like states, doesn’t prove that these experiences are anything like ours, or that these creatures are necessarily having an ‘experience’ at all.
Van Swinderen himself is not certain that insects are conscious in a way we might relate to. But he sees Drosophila as a chance to investigate the origins of subjective experience in the animal kingdom – there’s no fire without a spark.

The psyche of bees

“You might want to tie back your hair,” says Andrew Barron, a neuroethologist at Macquarie University’s Minds and Intelligences Initiative in Sydney. Neuroethologists study the neural mechanisms of animal behaviour.

It’s a month after my visit to Brisbane, and this time I’m chasing the psyche of an altogether different insect.

“Don’t worry, we’ve always got EpiPens onsite,” adds Barron’s PhD student, Théo, who strikes me as someone who has felt the keenness of a bee sting many times before.

I’ve pulled my hair up and under a giant beekeeper’s hat, my head and shoulders veiled. But my arms are bare on this sweltering January day, a fact about which no one seems particularly concerned.

The metal gate swings open and the three of us step into a giant, house-sized cage, filled with thousands of honeybees. Barron asks me not to step any further, because this particular hive is a little ‘spiky’. The lexicon suggests that hives, like people, have minds of their own – and this one has a short temper.

At the near end of the cage, Dr Marie Geneviève Guiraud, a researcher at the Institute, has set up a small white box on a trestle table. Inside the box is a miniature arena, in which she tests whether bees can distinguish between different human faces, rewarding correct answers with sugar water. (Spoiler alert: they can.)

Next to the box, a single bee is sitting patiently, a small, square chip fixed to her abdomen. This is the bee Guiraud has been training, and she tells me she’ll often find her there waiting, obedient as a trained puppy.

In the insect world, bees have a monopoly on charisma – famously intelligent, admirably cooperative, and cheerfully patterned. Along with Drosophila, they’re also some of the most widely studied insects, in part because their cooperative nature and work-horse mentality makes them easy to train.

Bees possess a particularly flexible intelligence. They can plan and remember complex routes, and make rapid, accurate decisions as they drift from flower to flower. Bee cognition is being studied to inform robotics and AI.

There is also evidence that bees may have some basic emotional states, such as the capacity for optimism and pessimism.

In one 2011 study, scientists agitated honeybees by vigorously shaking their containers to simulate a predatory attack. Agitated bees were more likely to predict a negative outcome when exposed to an ambiguous stimulus than unmolested honeybees exposed to the same stimulus. The agitated bees also displayed lower levels of dopamine and serotonin, neurotransmitters associated with pleasure and happiness in humans.

“I think it’s at least reasonably likely that bees and some other insects are conscious,” says Lars Chittka, a neuroethologist at Queen Mary University (QMU), London, and author of the book The Mind of a Bee, though he acknowledges it’s impossible to prove.

A 2022 experiment from Chittka’s team at QMU showed that bumblebees will go out of their way to roll wooden balls around, despite no obvious incentive for doing so, with all the hallmarks of playfulness. And younger bees roll the ball more often than older bees, just as older mammals play less than their young.

“They return to this activity again and again, when there’s no reward present, so that’s a hint that they enjoy the activity itself,” he says.

In 2016, Barron, who heads up the Macquarie Initiative, co-wrote a paper with Colin Klein, now a philosopher of neuroscience at the Australian National University, arguing that insects may well possess at least a basic form of subjective experience.

Their argument centred on the midbrain, a small part of the brainstem at the very centre of the brain. This handy part takes in sensory feedback from the outside world, and uses it to create an internal simulation of an animal’s position in space.

Barron and Klein argue that this representation of the world, as a physical space through which a ‘self’ moves, is enough to make subjective awareness – and structures in the tiny insect brain perform a similar function.

Other ideas of consciousness

“While the majority of philosophers and scientists think [phenomenal consciousness] is relatively primitive, in other words that’s where consciousness began and other computational, intellectual forms of consciousness arrived later, I think it’s the other way around,” says Nicholas Humphrey, a renowned English neuropsychologist who has been working away at the problem of consciousness for most of his life.

In the 1960s Humphrey, then a talented young PhD, began working with a lab monkey called Helen. Helen had had her visual cortex removed – the part of the brain that, in mammals, is responsible for processing visual information from the eyes. She could distinguish between light and dark, but could not seem to see shapes or distance.

In mammals and birds, the visual cortex is the main brain region involved in sight, but we also share a second, more ancient visual pathway with other animals such as fish, reptiles, and amphibians. In most animals, this pathway travels from the eyes to a region of the brain called the optic tectum; in mammals, it travels to the superior colliculus, the optic tectum’s evolutionary descendant.

Helen’s superior colliculus was intact and, through hours of observation, Humphrey suspected something interesting was going on with her vision. While Helen behaved as if she were blind – staring into space, colliding with objects, and moving cautiously in new spaces – she would sometimes reach for items Humphrey placed in her view.

Over several years, Humphrey trained Helen to negotiate obstacles, navigate the room, reach for fruit and nuts, and climb trees. When she was nervous or overwhelmed, her newfound visual abilities seemed to vanish, and she would behave as though blind again.

What Helen was living with was a neurological phenomenon we now know as ‘blindsight’, which also occurs in humans. Human blindsight patients who have damage to the visual cortex believe they cannot see – they have no conscious sensation of seeing. But, when asked to locate or identify an object placed within their visual field, they show much higher accuracy than if they were simply guessing.

For Humphrey, blindsight began to seed an idea about consciousness. Was it possible that animals like frogs were ‘seeing’ like Helen? Was it possible to have perceptions without sensations – to see without seeing?

If animals with an optic tectum but no visual cortex are capable of sight, but lack the corresponding sense of seeing, the same might be true for other sensations. In some animals, sensory information, like other major bodily processes, might exist solely in the realm of the subconscious. If true, those creatures would lack sensations altogether.

Humphrey believes phenomenal consciousness – the rich, vibrant experience that sensations give – is a recent adaptation present only in birds and mammals, and that it evolved to help those creatures negotiate complex social environments. Knowing your own inner world is crucial to operating in what Humphrey calls the “society of selves”.

“I think phenomenal consciousness is a sophisticated brain operation,” Humphrey says.

When it comes to other creatures, including lobsters, crabs, fruit flies, and bees, Humphrey believes they, “just don’t have this feeling, living in the present tense of sensation – they have a more robotic consciousness”.

But Chittka believes the accretion of pieces of evidence that hint at emotion and sensation in insects are unlikely, taken together, to be an accident.

“If you were asking this question about robots or computer programmes, then yes you can get them to pretend to be sentient,” says Chittka. “But I don’t think that nature has room for the kind of profligacy to generate beings that just pretend they feel something.”

On pain and suffering

When the experiment is over, the fruit fly’s prospects of a normal life are nil, so Gökaydin will euthanise her in the most humane way he knows how: the squish method.

Australia does not publish annual figures for the number of animals used in lab research, but global estimates suggest nearly 200 million creatures are tested on in labs worldwide each year.

The term animal here is not all-inclusive. Biologically, the animal kingdom encompasses all multicellular, eukaryotic organisms that consume, reproduce, and breathe oxygen, but UK law, for example, only classes vertebrates and cephalopods as animals, based on this contested concept of sentience. That means that universities and research centres try to use “lower” species like worms and insects wherever possible.

Drosophila, in particular, are a darling of the research world. They live fast, die young, reproduce prolifically and have just four chromosome pairs, making them simple creatures to study. Countless numbers of them have given their lives to science: six Nobel Prizes have been awarded to Drosophila scientists alone.

Meanwhile, around 23 billion animals are factory farmed annually, and the burgeoning insect protein market is forecast to reach US$9 billion by 2030, to feed a growing population in the face of climate change and biodiversity collapse. That’s not to mention the gruesome toll of pesticides, which lead to a harrowing death for insects.

Science and agriculture both have the unenviable task of balancing their ethical responsibilities to humans and to animals. Since the science of animal consciousness is so unsettled, most invertebrates remain unprotected by welfare legislation. Jeff Sebo, a philosopher at New York University, would like that to change.

“My view is that as long as a being has a non-trivial chance of being conscious, we should give them at least some consideration when making decisions that affect them,” he says. “A one per cent chance that insects are conscious means a one per cent chance that we might be causing trillions of insects per year pain and suffering.”

Both Sebo and Birch were among the authors and signatories of the New York Declaration on Animal Consciousness. That statement, published by a group of philosophers and scientists in April this year, argued that evidence for consciousness was widespread in the animal kingdom, and may well extend to insects.

For Birch, our failure to empathise with insects is really a failure of imagination.

“We struggle to engage with them as a fellow sentient being, and I’m sure the feeling is mutual,” he says. “We’re this giant, looming presence in their lives, as inscrutable to them as they are inscrutable to us.”

But Birch is hopeful that a mounting body of evidence will give policymakers pause.

“There’s this sea change in the culture of science, and people are now daring to ask questions about animal consciousness,” Birch says. “We hope this will send a signal to policymakers that they cannot simply ignore the interests of animals completely, because they’re capable of suffering.”