The most prominent scientific theories of consciousness are converging on the idea that it is related to a certain kind of information processing, in which multiple strands of data are drawn together, and that it is dependent on a certain kind of network architecture. Arguably the most popular theory along these lines, information integration theory by Giulio Tononi, effectively assumes that consciousness is a continuum across the animal kingdom. If so, even the lowly nematode worm, with a few hundred neurons, will have some, albeit minimal, level of consciousness. If something approximating this theory proves correct, it has huge implications for our relationship to all animals on the planet.
But even if we assume that there is a continuum of consciousness, this is of limited use in helping answer questions of animal rights. For instance, a worm may indeed have a capacity for some consciousness, but the way it experiences the world may be infinitesimally limited compared to human awareness. More pertinent for ethics is the scientific exploration of whether other animals have advanced forms of consciousness, such as self-awareness. This can be tested using the mirror test: A spot of paint is placed on an animal’s face, and it is then presented with a mirror. Many animals will simply attack or try to escape from the apparent foe in the mirror, but a select few will recognize themselves, as demonstrated by them trying to remove or at least examine the strange spot. The current list of animals that clearly pass this test includes chimpanzees, orangutans, gorillas, dolphins, elephants, pigs (on a modified version of the test), and even magpies. But this list of species is sure to grow as more animals are tested in ways that are most appropriate for them.
Another marker of an advanced consciousness is something called metacognition, the ability to be aware of your own mind and report on it, for instance by saying: “I’m sure I saw that cat in the woods,” or “You might have seen a cat, but I didn’t spot anything.” In human experiments, it is seen as definitive evidence of consciousness. But we are not the only species to have this skill.
Metacognition in other species is usually measured using a gambling task: An animal makes a decision about a stimulus and can then press either a high-risk button that promises a large food reward if the decision was correct but food restriction if it was wrong, or a low-risk button with a meager reward regardless of whether the animal is right or wrong. If the animal has significant metacognition—in other words, if it knows whether it is just guessing or if it has solid knowledge about a given stimulus—then it should usually press the high-risk button when it knows the correct answer and the low-risk one when it’s wrong. This is exactly what several other species, including the great apes and monkeys, do. These species demonstrate an advanced form of consciousness that in humans is definitive evidence of our awareness.
My take on all this data is that it is extremely likely that all the species that can recognize themselves in the mirror or show metacognitive abilities have an advanced form of consciousness. But for any species that hasn’t yet passed these tests, we simply don’t know whether they lack the ability or just haven’t been tested appropriately. The cautious attitude, I believe, is to assume that all mammals and the octopus at the very least, but possibly many more species, have a significant capacity for consciousness.
Consequently, I am a vegetarian, as are several prominent consciousness researchers. I believe it would be ethically consistent for us to extend our own rights to life and freedom from torture to any species that can recognize itself in the mirror, show clear metacognition, or even demonstrate extensive tool use. Barring all these animals from the food industry and passing laws to protect them based on their consciousness would be a radical step and not one that I can see any political leader advocating anytime soon. Nevertheless, it would be a consistent and caring departure from the way much of society currently views animals, and it would acknowledge the advances in our scientific understanding of the mental lives of these other species.
Consciousness research informs other political issues as well. For instance, how can we assess the level of consciousness remaining in someone who has suffered severe brain damage and is in a vegetative state? At what point should we let such patients die? And it is possible that in the decades to come, we might also need to start thinking about how we assess artificial forms of consciousness and what rights we consequently need to bestow on such beings.
Therefore, not just for its own sake but for evaluating many ethical dilemmas, consciousness science is a vital field. Anyone interested in key political debates may want to keep a close eye on its progress in the years to come.