Opinion: Making sense of sentience

With a draft UK Animal Welfare Bill looking to put the concept of ‘animal sentience”directly into law and an ongoing debate about the levels of pain different species might experience, psychologist Stuart Derbyshire asks if we are really observing pain in some animals or some other reaction.

Recently, the government of Switzerland ordered that lobsters should no longer be dropped alive into boiling water in case the lobster feels pain. Much of the evidence that lobsters might feel pain is extrapolated from observations of other crustaceans, such as hermit crabs, which avoid areas where they previously received electrical shocks, and will leave a protective, sheltered, area when shocked. It is also noted that lobsters and other crustaceans will move away from intense heat.

Still, how much of a ‘pain’ experience can we expect a lobster to have with such a sparse nervous system?  The avoidant behaviour of crustaceans is certainly consistent with an experience of pain. Locusts, for example, have been observed to continue munching on vegetation even while they are themselves being eaten, which is much less consistent with pain experience. Avoidant behaviour, however, is far from demonstrating an experience of pain. Even the humble fruit fly drosophila (otherwise known as a maggot) will bend and roll away if you light a naked flame next to it.

The lobster beats the maggot because it does have a more sophisticated nervous system involving centralized bundled nerve endings known as ganglia. Arguably those centralized bundled nerve endings can be called a brain, but that brain is notably puny – about the size of a grasshopper brain. Based on that, it seems unlikely that the lobster will be capable of much experience that we could relate to as common.

Nevertheless, lobsters do have an opioid system, which regulates pain in humans. Morphine is the compound that mimics our natural opioids and morphine is a powerful painkiller. Injecting morphine into crabs makes them less responsive to electrical shock, and less likely to emerge from a protective shelter. To my knowledge, nobody has tried injecting lobsters with morphine, but I would expect that such injections would make the lobster similarly less likely to move away from intense heat.

People in pain report a physical sensation (throbbing, aching, stabbing and so on) and an unpleasantness. If the pain is severe or continues for a long time, that unpleasantness becomes a suffering that can entirely consume the being of that person. People in pain also face the dread and fear of what might happen next (death or disability). For humans, therefore, pain is complex and multidimensional. That pain involves large amounts of our cerebral cortex, the outer large part of our brain, which is completely absent in lobsters and crustaceans.

Pain is also a high-level subjective experience that draws on our memory, attention and general understanding of what bodies are, how they work, and how they can be broken or permanently damaged and destroyed. Pain is often accompanied by a tremendous anxiety connected to the existential recognition of the dangers that pain might be indicating. A life suddenly interrupted, projects that will never be finished, loved ones who will never again be seen – everything finishing in a blistering blaze of final agony.

We might never be certain exactly what, if anything, a lobster might feel when plunged into boiling water. We can, however, be certain that lobsters do not live the kinds of lives we live, do not have the kinds of brains we have, and so cannot experience the kind of self-reflective recognition of being in pain that we can have when plunged into boiling water. A lobster cannot experience their final journey as painful like us because that demands too much from the lobster – labelled sensations, suffering, reflection, regret, fear, angst, anger, sadness, and so on.

Lobsters can generate defensive reactions when faced with environmental threats to their bodily existence, but that is not the same as being in pain and knowing one is in pain. We can make laws to avoid such defensive reactions if we want to, but we shouldn’t make those laws based on the idea that lobsters can feel pain like us.

Stuart Derbyshire

Stuart Derbyshire is an Associate Professor in the Department of Psychology and A*STAR-NUS Clinical Imaging Research Centre, National University of Singapore stuart.derbyshire@nus.edu.sg