Elephants cooperate to solve problems. Chimpanzees teach youngsters to make tools. Even octopuses seem to be able to plan. So should we humans really be surprised that "consciousness" probably does not only exist in us?

This privileged state of subjective awareness in fact goes well beyond Homo sapiens, according to the new Cambridge Declaration on Consciousness (pdf), which was signed last month by a group of cognitive neuroscientists, computational neuroscientists, neuroanatomists, neuropharmacologists, neurophysiologists who attended the Francis Crick Memorial Conference on Consciousness in Human and non-Human Animals at Cambridge University in the U.K.

"The weight of evidence indicates that humans are not unique in possessing the neurological substrates that generate consciousness," the scientists wrote. "Non-human animals, including all mammals and birds, and many other creatures, including octopuses, also possess these neurological substrates."

The octopus is the only invertebrate to get a shout-out at all. And plenty of research has been accumulated to back up this assertion. A 2009 study showed that some octopuses collect coconut shells to use as portable shelters—an example of tool use, according to the researchers. Other research has documented sophisticated spatial navigation and memory. Anecdotal reports from researchers, such as Jennifer Mather, describe watching octopuses in the wild make errands to collect just the right number of rocks to narrow the opening to a desired den. And laboratory experiments show a distinct change in behavior when octopuses are kept in tanks that do not have enough enrichment objects to keep them stimulated.

What was keeping scientists from accepting the existence of consciousness outside of our own family tree? Simple brain anatomy. Older models of brain activity lodged complex, conscious experiences—like musing about a piece of music or reminiscing about a piece of cake—in our highly evolved cortex. But, as the authors of the new declaration noted, many nerve networks involved in "attentiveness, sleep and decision making appear to have arisen in evolution as early as invertebrate radiation, being evident in insects and cephalopod mollusks (e.g. octopus)."

Even emotions (or, according to the declaration, their "neural substrates") are not dependent on an animal having particular brain structures, such as our cortex, after all. In fact, many other neural regions are activated when we emote and "are also critically important for generating emotional behaviors in animals," the scientists noted.

That does not necessarily mean that you could have a distraught octopus or an elated cuttlefish on your hands. But this new, formalized conception of consciousness does suggest that the octopus has used its own, more foreign-looking brain to develop some sense of subjective experience.

"Exactly how organized brain matter gives rise to images and sounds, lust and hate, memories, dreams and plans, remains unclear," Christof Koch, chief science officer at the Allen Institute of Brain Science, and co-presenter of the new declaration, recently wrote in the Huffington Post. And although brain structures, such as the cerebral cortex, in mammals seem to be highly conserved evolutionarily, Koch noted, other organisms, such as birds and cephalopods force us to reexamine other neural components of consciousness. "The challenge that remains is to understand how the whispering of nerve cells, interconnected by thousands of gossamer threads (their axons), give rise to any one conscious sensation," he wrote.

And so, with the new declaration (and with apologies to David Foster Wallace), science has considered the octopus. And found it conscious. …Now we just need to figure out what, exactly, the octopus experience is.

Illustration courtesy of Ivan Phillipsen