We know we are – but what else is conscious too?

If dogs and crabs are both conscious, is it in the same way?

Elliott Erwitt/Magnum

By Matthew Cobb

WHEN I was a psychology student in the 1970s, there was a widespread view that the study of consciousness was a passport to irrelevance. Now many scientists grapple with it and anyone who cracks the problem can certainly expect a call from Stockholm.

Philosophers have pondered the issue for millennia and, understandably, are not going to be shoved aside by newcomers armed with electrodes and MRI scanners. Michael Tye, however, is not a neuroscientist, but a physicist turned philosopher, who for the last decade or so has been considering the evidence we use to determine whether other organisms are conscious.

In Tense Bees and Shell-Shocked Crabs, Tye confidently applies his method to animals, plants and robots. Because there is no accepted measure of consciousness, Tye resorts to what philosophers do best: rigorous thinking and logical argument. “Animal consciousness,” he says, “is just animal experience.” For this to be other than tautology, it must mean that consciousness equals experience equals sensation. That would imply that the simplest sensory system, capable of responding to external stimuli and modulating that response (that is, sensing and learning), is conscious.

If provable, this would indeed be a strong solution to the question of consciousness, but it is not one Tye adopts. Although he peppers his argument with descriptions of various neurons and brain structures, he operates with an obvious rule of thumb (probably shared by many readers) that is linked to apparent degrees of neuronal complexity. Thus he considers all vertebrates conscious, although one of his criteria, the existence of a certain class of pain receptor, does not fully apply to cartilaginous fish. Tye recognises the problem but skips away, leaving it unresolved.

He also thinks that the best explanation of bee behaviour is that they are conscious, though he is less certain about Drosophila. Strikingly, he considers it “a great leap of faith” to think that worms, which do not have many neurons, can “genuinely feel pain”. (The phrase “genuinely feel” is oddly vague for a philosopher.)

“Strikingly, Tye considers it would be a great leap of faith to assume that worms can genuinely feel pain”

Tye highlights learning and behavioural plasticity, opening the book with the bold claim that a small dog that whines to be lifted onto an inaccessible bed has self-awareness because it knows it cannot reach its desire unaided.

But it is not clear why this dog is any different from the set of cockroach neurons studied in 1962 by Cambridge University neurobiologist Adrian Horridge. His experiment showed the cockroach “learns” to keep its leg out of electrified water to avoid a shock. This seems like a similar behaviour to that of the dog: the cells “know” what they want (in this case, to avoid shock). Tye does not discuss this challenging experiment; presumably he would class it as “unconscious learning”, a category he applies to a number of counter-examples, excluding them from his central argument without further discussion.

Frustratingly, Tye has not located his exploration of consciousness in an evolutionary framework. Instead, he seems to suggest that if a structure does something in a complex organism, then a similar structure must do the same thing in a simpler organism. But evolution alters function according to selection pressures. A more solid grasp of evolutionary biology would have nuanced Tye’s arguments and tempered his judgements, bringing them closer to those of most of the scientists he quotes.

This is an entertaining and stimulating book that may profoundly irritate many scientists; students should be warned that university science generally employs different kinds of evidence and argument than the philosophical approach used here. I hope Tye will collaborate with scientists on experimental tests of his views. That would be far more convincing than any amount of argument.

Tense Bees and Shell-Shocked Crabs: Are animals conscious?

Michael Tye

Oxford University Press

This article appeared in print under the headline “What else is conscious?”