We tackle the age-old question: Do animals experience consciousness?

Cogito ergo sum.

‘I think, therefore I am.’ Descartes’ famous statement from 1637 was possibly one of the first attempts at philosophically determining what consciousness is exactly. He believed that just the capability of thought proved consciousness is there. But what is consciousness, really?

We know it’s there—we live it every day. It’s that intangible entity (or rather, experience) allowing us, in a shout-out to Descartes, to form thoughts. It allows us to enjoy the shiver of a perfectly shaped movement of classical music, to feel the crushing weight of depression at the end of a relationship, or the calm satisfaction that comes from watching a sparkling and serene sunset. Some argue it’s what allows us to dream; lucid dreaming in particular relies on some level of consciousness while asleep to control the experience. But scientists historically have struggled fitting all these experiences into concrete research depicting exactly how and why consciousness exists.

At this point in modern research, neuroscientists can generally agree to two accepted theories.

The Global Workspace and Integrated Information theories

The first, developed by Bernard Baars of the Neurosciences Institute of La Jolla, California, is the attractively named Global Workspace theory. Baars basically says that the brain functions with a ‘blackboard’ architecture, where everything someone experiences—like the memory of an event or the visual appearance of an apple—is stored in a common location (the blackboard). Information from this spot is then broadcast around the brain as needed, representing consciousness.

Baars’ theory is more of an explanation for how consciousness works; the second theory, by Giulio Tononi from the University of Wisconsin-Madison, focuses more on determining whether something is conscious or not. His work is called the (equally attractive) Integrated Information theory. According to Tononi’s research, consciousness forms from a large amount of information that your brain weaves together. It’s beyond our control how our consciousness forms. For example, we can’t choose to just see things in shades of blue—the information integrating in our brains makes that choice for us.

An outlying theory links brain size with consciousness—86 billion neurons comprise the human brain, while a mouse touts only 75 million (that’s more than 1,000 times less). Bigger brains equal more complex thoughts and neurological interactions, which equal our capability of consciousness. But that doesn’t explain the phenomenon many of us see every day: animals in the world around us expressing emotion, learning tasks, understanding complex concepts. Plus, the cerebral cortex in the human brain is integral to our consciousness. If someone were to get a cortex lobotomy, conscious thought wouldn’t come nearly as easy. So essentially, brain size does not apply in the pursuit of consciousness.

Cats, for instance, have 300 million neurons in their adorable little brains. But of many animals, cats seem to exhibit the most signs of consciousness—even though they have substantially less neuron power. Any feline lover knows that cats really only do things if they want to, something that requires conscious decision-making ability. And they are incredibly perceptive of their owner’s emotions, offering comfort when needed, showing excitement after long absences, and reacting to subtle body language cues.

Dogs are much the same (although, sorry to tell you dog people, they have less than half the brain neurons of cats), exhibiting complex emotions like frustration, fear, sadness over a lost loved owner, and not to mention the occasional extreme display of guilt.

Even the friendly octopus exhibits signs of consciousness, being able to make plans and solve problems, like collecting shells to make portable shelters, finding the proper number of rocks to use while tightening the entrance to their underwater den, and even discovering how to escape from closed containers.

Gorillas can communicate with sign language and are able to create their own signs for objects and emotions. Horses can express themselves through paint. Bonobos (formerly called pygmy chimpanzees) show how they feel through a wide range of facial expressions. New research has shown that even plants can possibly learn, remember, and react in a way humans can understand—supposedly they also have senses and are able to communicate with each other. Nearly every living organism on the planet interacts with a species-specific language that can include everything from body language to facial cues to audible noises like buzzing and whining.

Moreover, if we were to look at self-awareness as a sign of consciousness, what Descartes was alluding to with his famous quote (although interestingly enough, Descartes did not believe non-humans were able to have consciousness), even more examples of potentially conscious animals pop up. The 1970s saw the advent of the mirror test, where a full-length mirror is placed in front of an animal and their reaction is examined. Elephants can recognise themselves in their reflection, rather than think it’s another elephant. Chimps will initially see their reflection as a threat, but then use a mirror to see hard-to-clean places on their bodies. Bottlenose dolphins, when presented with various mirrors, will routinely seek out the most clear and flat reflective surface to inspect themselves in. Even European magpies—birds that have no cerebral cortex—were able to recognise themselves in the mirrors and try to clean off dirty spots on their feathers that they saw in their reflections.

Consciousness, an on-off phenomenon?

Scientists have rallied behind the idea that creatures other than humans are fully capable of being both self-aware and conscious—so much so that in 2012, a group of cognitive scientists, neuropharmacologists, neurophysiologists, neuroanatomists, and computational neuroscientists attending the Francis Crick Memorial Conference on Consciousness in Human and Non-Human Animals signed a document (The Cambridge Declaration on Consciousness) stating that all mammals, birds, and other creatures have a human’s level of consciousness. According to the scientists in attendance at the conference, we are far from unique in the way we perceive and interact with the world.

So is consciousness an on-off phenomenon? Or is it a spectrum stretching out across all the world’s living creatures? If Tononi’s theory is right, consciousness exists in various degrees in every organism. His calculations on the brains of various creatures show differing measurements of integration, meaning that those traits of animal behaviour mentioned above very well might show certain levels of consciousness. Related studies by neuroscientist Sid Kouider at the Laboratoire de Sciences Cognitives et Psycholinguistique in Paris have put Tononi’s theory to work and found that what we previously considered to be some of the most reflexive beings, babies, are actually reacting with conscious awareness to different stimuli as early as five months old.

The bottom line, though, is that we’re still unable to be inside another animal or creature’s head enough to know if they experience consciousness the same way we do. We can’t hear their thoughts—if there are any at all to hear. So it comes down to a matter of our own perception. The next time your cat cuddles up to you when you’re sad, consider that it might be because she consciously knows you’re upset and is making an effort to help. It could make you see your pet (and all other creatures) in a whole new light.