麻豆传媒

David Pe帽a-Guzm谩n

Princeton University Press

HEIDI the octopus is dreaming. As she sleeps, her skin changes from smooth and white to flashing yellow and orange, then to deepest purple and, finally, to a series of greys and yellows, criss-crossed by ridges and spiky horns.

David Scheel, Heidi鈥檚 human carer, has seen this pattern before in waking octopuses: Heidi, he says, is dreaming of catching and eating a crab.

The story of Heidi鈥檚 dream, told in the 2019 documentary , provides the starting point for a barnstorming new book, When Animals Dream: The hidden world of animal consciousness by David Pe帽a-Guzm谩n.

A philosopher at San Francisco State University, Pe帽a-Guzm谩n delivers an intellectual tour de force as he explores the extraordinary world of non-human imaginations.

The Roman philosopher-poet Lucretius thought that animals dreamed. So did Charles Darwin. The idea only lost respectability for about a century, roughly between 1880 to 1980, when the reflex was king and behaviourism ruled the psychology labs.

In the classical conditioning model developed by Ivan Pavlov, it is possible to argue that trained salivation at the sound of a bell is just a reflex. Later studies relied on a different method, called operant conditioning, in which a rat, say, has its behaviour reinforced either positively or negatively.

But none of these studies ever banished the notion that animals had imaginative interior lives. The experimenter can claim as much as they like that their trained rat is 鈥渃onditioned鈥�, but that rat running through its maze looks for all the world as though it expects something.

In fact, there is no 鈥渁s though鈥� about it. Pe帽a-Guzm谩n, in a book rich in detail about experimental work, describes how rats, during their exploration of a maze, will 鈥� all of which is revealed by distinctive activity in their brains鈥� hippocampi.

Evidence that animals have a kind of imagination is intriguing, but what really dragged the study of animal dreaming back into the light was a better understanding of how humans dream.

From the 1950s to the 1970s, dreams were seen as mere random activity in the pons, a part of the brainstem that links the brain to the spinal cord. Now we know that dreaming involves many more brain areas, including the parietal lobes, which are involved in the representation of physical spaces, and the frontal lobes, which are responsible for emotional regulation, among other things.

So which animals dream?Pe帽a-Guzm谩n鈥檚 list is long, but includes mice, dogs, belugas, platypuses, ostriches, penguins, chameleons, iguanas, cuttlefish and octopuses. 鈥淭he jury is still out on crocodiles and turtles,鈥� he adds.

While the brain structures of these animals may be nothing like our own, studies of sleeping brains do expose startling commonalities, suggesting, perhaps, that dreaming is a skill upon which many branches of the evolutionary tree have converged.

Pe帽a-Guzm谩n asks big questions. When did dreaming first emerge and why? By which paths did it find its way into so many branches of the evolutionary tree? And, perhaps the biggest question of all, what do we do with this information?

For him, dreams are morally significant because 鈥渢hey reveal animals to be both carriers and sources of moral value, which is to say, beings who matter and for whom things matter鈥�. In short, dreams may imply the existence of some sort of self.

The issue of whether or not that self can think rationally, act voluntarily or talk about its dreams, just like a human, is neither here nor there. The fact is, says Pe帽a-Guzm谩n, animals that dream 鈥渉ave a phenomenally charged experience of the world鈥� they sense, feel and perceive鈥�.

Starting from the tricky assertion that Heidi the octopus dreams of fresh crab suppers, Pe帽a-Guzm谩n assembles strong evidence with which he makes a short, powerful, closely argued case for 鈥渁nimalhood鈥�. This book will change minds.