You’re cooking dinner, distracted, and your hand brushes a hot pan. Nerve signals race to your spinal cord and back to yank your arm away in a fraction of a second, with no thought required.
Then comes the pain. A sharp, spreading sting gives way to a pulsing ache, and you cradle your hand and run it under cold water until it subsides. That felt experience is distinct from the reflex that preceded it. While the reflex moved your body out of danger, pain drives you to protect the wound, recover, and learn to avoid similar mistakes in the future.
We readily accept that other people feel pain by reading cues in their behaviour, like the inspection and nursing of an injury. We extend this to some animals too – a dog licking its paw or a cat favouring a limb rightly stir our sympathies. But what happens when we turn that lens on animals far less like us?
In our new study, published in Proceedings of the Royal Society B, we searched for behavioural signs of pain in house crickets, one of the most widely farmed insects. After applying heat to an antenna, we found that crickets didn’t just reflexively flinch and recover. They nursed the harm, returning again and again to groom the affected site, much as we rub a burned hand.
The frontiers of feeling
French philosopher René Descartes considered animals unfeeling biological machines, and for centuries the circle of moral concern barely extended beyond our own species.
But the boundaries have steadily crept outward. Recognition that mammals experience pain came first, followed by birds. Fish too, once assumed to lack the necessary brain structures, are now widely accepted as capable of pain-like states.
The leap into invertebrates has been greater and more contentious. Their nervous systems bear little resemblance to our own, so arguments from brain anatomy alone don’t carry us far. Instead, we look to behaviour. Does the animal respond to harm in ways that go beyond reflex, ways that are flexible, persistent, and sensitive to context?
Over the past decade, testable indicators for pain in non-humans have been developed and are increasingly accepted. These include learning from unpleasant events, trading off harms against rewards, and actively protecting the site of injury. Evidence meeting these criteria helped crabs and lobsters gain legal recognition as sentient under United Kingdom law in 2022.
Among insects, the evidence has been accumulating fast. Yet most of this evidence comes from bees. Bumblebees weigh the risk of harm against the richness of a food reward, and groom the site of an injury. Honeybees learn to associate particular smells with harmful stimuli and avoid them.
Far less attention has been paid to Orthoptera, the group that includes grasshoppers, locusts and crickets. That gap matters, because the house cricket (Acheta domesticus) is the world’s most widely farmed insect, with more than 370 billion reared annually.
Afton Halloran
Do crickets feel pain?
We tested 40 male and 40 female crickets, each experiencing three conditions in random order: a hot probe to a single antenna (65°C, to activate damage receptors but not cause lasting injury), the same probe unheated, or no contact at all.
We filmed their behaviour for ten minutes. Observers scoring the footage did not know which treatment any animal had received.
The results were clear. After the hot probe, crickets were more than twice as likely to groom the affected antenna compared to controls, and spent roughly four times longer doing so.
Could this simply reflect general disturbance rather than targeted care? Unlikely: grooming was directed specifically at the heated side, not spread evenly across both antennae as it was after gentle touch or no contact.
And the behaviour wasn’t a brief, reflexive reaction. It was elevated from the outset and tapered gradually over minutes, much like rubbing a burned hand as the felt sting slowly fades.
Small minds, big feelings
Subjective experience cannot be directly observed in any animal, not even humans.
But we have shown crickets respond to harm in a way that satisfies a key criterion many scientists and philosophers use to infer pain: flexible, directed self-protection. Combined with the knowledge that crickets possess damage receptors, can learn to avoid harms, and respond less to injury under morphine, the weight of evidence for an inner life is growing.
The practical stakes are real. Hundreds of billions of farmed insects are slaughtered each year by freezing, boiling and baking. Pesticides kill trillions more, optimised for lethality with no consideration of potential suffering.
If we take a precautionary approach, credible evidence of suffering should motivate proportionate protections well before we are certain.
Insects have been around for more than 400 million years and are far more behaviourally and cognitively sophisticated than once assumed. The question, then, may not be whether some insects feel, but why we ever assumed they couldn’t.
