Consciousness in octopuses and invertebrates
Explanation
Octopuses and other cephalopods (squid, cuttlefish) represent one of the most fascinating and challenging cases for the theory of consciousness. They are invertebrates, evolutionarily separated from vertebrates over 600 million years ago, and have independently developed complex nervous systems: approximately 500 million neurons, two thirds of them distributed in their arms, not centralised in the brain. If they have consciousness, its form is probably very different from that of mammals.
Behavioural observations suggest remarkable cognitive capacities. Octopuses solve problems (opening jars), learn by observation (in some species), use tools (coconuts as shelter), recognise individual humans, play, and have distinguishable personalities. Their behaviour suggests planning, evaluation, flexible decisions. Peter Godfrey-Smith, in Other Minds (2016), philosophically explores what octopuses tell us about the nature of mind and the possibility of radically alien subjective experiences.
The distribution of the nervous system raises unique questions. If two thirds of the neurons are in the arms, what kind of bodily coordination is needed? Do the arms have some degree of sensorimotor autonomy of their own? How does that integrate with the central brain? Some researchers speculate that the conscious experience of an octopus could be extraordinarily distributed, not centred on a single point, which is hard for us to imagine but biologically plausible.
Other invertebrates also show signs of cognitive capacities and possible subjective experiences. Bees have sophisticated behaviours (communicative dances, navigation, learning), learn complex tasks, and show emotional responses (studies of optimistic/pessimistic states in bees). Lobsters and crabs show behaviours consistent with suffering (analgesia-seeking, avoidance, physiological changes under stress). Octopuses, bees and other invertebrates are increasingly considered serious candidates for some forms of consciousness.
For the theory of consciousness, these cases broaden the space of the possible. If consciousness arose, it probably did so more than once in evolutionary history (vertebrates and cephalopods, at least). This suggests that its material conditions may be varied: a mammalian cerebral cortex is not needed to have it. This lends weight to more inclusive theories (such as IIT, which quantifies informational integration regardless of the exact substrate) and offers critical data for theories that limit consciousness to specific structures.
Ethical implications are growing. The United Kingdom recently included cephalopods and decapod crustaceans in its animal welfare legislation, based on a scientific review concluding that they probably experience pain and suffering. This raises practical (boiling lobsters alive, octopus capture, etc.) and philosophical questions: if our moral intuitions rest on the possession of consciousness, we must extend consideration to animals very different from us, whose minds we cannot imagine.
Strengths
- Evidence of consciousness (or proto-consciousness) in remote lineages.
- Detailed biological data on the nervous system.
- Constrains general theories of consciousness.
- Clear ethical implications regarding invertebrate welfare.
Main critiques
- Phenomenological access even more limited than in mammals.
- Defining consciousness in such different architectures is difficult.
- Anthropomorphisation tempting.