Self-awareness is a measure of intelligence - and most living species on the planet do not possess it. Of the hundreds of animals tested so far, only 10 animals have been proven to have any measurable degree of self-awareness:
So how exactly do you qualify for self-awareness?
In humans, it means having conscious knowledge of your own character, feelings, motives and desires - and imagining how others might perceive you. It extends right up to having self-conscious emotions like pride or shame.
In the wider animal kingdom, we've lowered the bar, mainly because it's so difficult to measure what an animal thinks and feels. Instead, we look for signs that they recognize they exist separately from other animals and the environment.
The best way to determine this scientifically is with the mirror test...
Developed in the 1970s, the experimenter discreetly marks the animal with a colored dye, or puts a colored dot on their forehead. The animal is then presented with a mirror and their reaction is observed.
If an animal is self-aware they'll turn and adjust their body to get a better view and touch the colored spot or try to remove it. This proves that the animal understands the reflection is its own.
Animals that fail the mirror test appear to assume the reflection is just another animal. They draw no correlation between the reflected movements or facial expressions with those of their own.
However, the mirror test is not bulletproof. Despite their intelligence, almost all gorillas fail the mirror test because they deliberately avoid making eye contact (as this is an aggressive gesture). As a result, they don't afford themselves the opportunity for any kind of self-recognition. One exceptional gorilla who has passed the test is called Koko (see below).
What's more, animals who had previously failed the mirror test have begun to pass it under specific circumstances (see rhesus macaques, below). This suggests that we need alternate, more reliable methods search for animals with self-awareness, beyond the simplistic mirror scenario.
Here are 10 animals with self-awareness according to the mirror test. By the end of this article you'll see why there are likely to be many more animals who may qualify for self-recognition, and it's only a matter of time before we identify them.
Humans are the most self-aware and generally nail the mirror test in infancy, around the age of 18 months old. In fact, studies have identified five different levels of self-awareness in children before they reach 4-5 years old:
Like all the great apes, orangutans make it to the list of animals that are self-aware. Indeed, it was a captive orangutan who first inspired the mirror test...
In 1838, when Charles Darwin was visiting London Zoo, he watched a female orangutan named Jenny throwing a tantrum after being teased with an apple by her keeper. He began musing on what the subjective experience of being an orangutan must be like. Besides noting how intelligent and human-like Jenny was, Darwin spied her gazing into a mirror, and realized she was fully aware that she was seeing a reflection of herself.
It wasn't for another 130 years, however, that Gordon Gallup Jr reenacted Darwin's observation with wild preadolescent chimps and termed it "the mirror test"...
Gallup's initial subjects - two male and two female chimpanzees - were each put in a room alone for two days. Then a full length mirror was added to the room and their reactions scrutinized.
Initially, the chimps (who had never seen a mirror before) made threatening gestures at their reflections. But eventually they began to use the mirror for self-directed responding behaviors, like grooming hard-to-see places, picking their noses, making faces and blowing bubbles at themselves.
Although gorillas generally fail the mirror test, one specific gorilla named Koko has passed it. Koko is famously known as the "talking" gorilla, recognizing more than 1,000 words in American Sign Language and 2,000 words in spoken English.
Born in 1971 in San Francisco Zoo, Koko is the subject of a groundbreaking science experiment to determine the true intelligence of gorillas. Although she can’t vocalize like a human, she can understand spoken words and communicate her thoughts and feelings with hand signals.
Her trainer, Dr Francine Patterson, has also seen her invent new signs of her own - like the combination of signs for "finger-bracelet" to describe a ring. Koko even demonstrated that she feels emotions much like a human being. She once asked if she could have a cat and chose out a gray male Manx as her pet, which she cared for as a baby. Later that year, the cat escaped and was hit by a car. When Patterson explained the cat had gone, Koko signed "bad-sad-bad" and "frown-cry-frown-sad". After that, Koko the gorilla was able to pick out two new kittens which became her surrogate babies.
Today, Koko is 42 years old and describes herself as a "fine-gorilla-person", amazing her friends and caregivers with her intelligence and emotional depth.
Aquatic mammals have also been awarded with mirror self-recognition. The set-up had to be tailored a little differently, of course...
In 2001, two Bottlenose dolphins were exposed to reflective surfaces after being marked with black ink, applied with a water-filled marker, or not being marked at all. The researchers predicted that the dolphins (who had previous experience with mirrors) would not show social responses, would spend more time in front of the mirror when marked, and would move to the mirror faster to inspect themselves.
All the predictions bore true. In fact, the Bottlenose dolphins went one step further by consistently selecting the best reflective surfaces to view their new markings.
The self-awareness observed in Bottlenose dolphins may result from their relatively large brains and advanced cognitive abilities (though not all dolphins have such large brains or are known for their problem solving skills).
The researchers also noted how the fact that both Bottlenose dolphins and primates share self-awareness - despite their profoundly different brain evolution and organization - represents "a striking case of cognitive convergence".
You may be surprised to know that elephants demonstrate self-awareness too. A study in 2006 involved placing an 8-foot mirror in the elephant enclosure at the Bronx zoo in New York, while researchers kept a close watch over the three inhabitants.
The elephants did not greet their reflections as if they were other elephants, but instead used the mirror to inspect themselves and the inside of their mouths. They also tried to look behind it, which showed they recognized the mirror was not merely an extension of the enclosure. Finally, one of the elephants passed the colored dot test by touching (with its trunk) a newly painted mark on its head.
Elephants were already known for their superior intelligence, complex social systems, ability to feel empathy, and altruistic behavior. Now they are the only non-primate land mammal which passes the mirror test to show true self-awareness.
Though the details were less publicized in the media, a 2001 experiment published in Behavioural Processes revealed the self-reflective nature of orcas (killer whales).
Using the same style of mirror test as with Bottlenose dolphins, orcas did indeed show signs of "contingency checking" in the mirror, reacting to the mark as if they expected their image to look different. Some signs of self-awareness were also seen in false killer whales, and the researches suggested that they appear to possess the cognitive ability for it.
Bonobos are an endangered ape species and more peaceful and social than the common chimpanzee.
In fact, genetically, they are most similar to us - and share many behavioral traits such as walking upright and having very similar facial expressions. Like humans, it is also easier to distinguish facial features between different individuals, such that humans can easily differentiate one bonobo from another.
They, too, have passed the mirror test, back in 1994. And like Koko the gorilla, two well-known bonobos have been taught language: Kanzi and Panbanisha have a vocabulary of about 400 words which they type using a keyboard of lexigrams (geometric symbols). They can also respond to spoken sentences.
Quite possibly our most intelligent cousins, the leading primatologist, Professor Franz de Waal, claims that bonobos are also capable of altruism, compassion, empathy, kindness, patience and sensitivity.
It was only recently, in 2010, that scientists accidentally discovered that monkeys can pass the "cognitive divide" between the highest primates and the rest of the animal kingdom.
Researchers had placed head implants in two rhesus macaque monkeys, in advance of doing a study on attention deficit disorder. To their surprise, the macaques - who would normally fail the mirror test by reacting to their reflection as if it were an invading monkey - showed clear signs of self-awareness.
The monkeys observed themselves in the mirror while grooming and examining their foreheads near the implant. They also examined parts of their body that they hadn't seen before and turned themselves upside down to do so. Finally, they grasped and adjusted the mirror to get an enhanced view. However, the self-realization had no permanence: when the mirror was covered up these behaviors disappeared.
The final (and quite unexpected) entry into the list of 10 animals with self-awareness is the European magpie. Not only is it the only bird to have passed the mirror test, it's the only non-mammal species, too. Go magpies.
Closely related to crows (who are also known for their intelligence, if not self-awareness) magpies officially gained self-awareness in the scientific archives in 2008.
A German study involved placing various colored dots on the necks of the birds where they couldn't see them. While the magpies didn't react to the feel of the dots, they began scratching their necks when placed in front of a mirror. Those with black dots, which were camouflaged against their feathers, didn't react at all.
It was once thought that self-awareness arises from the neo-cortex of the brain - but magpies don't have one. Franz de Waal points out that magpies do, nonetheless, have large brains with lots of connectivity. "Magpies are known for their ability to steal shiny objects and to hide away their loot," he said. "It's not too far-fetched that a master thief like a magpie has that perspective-taking ability."
If self-awareness is a conscious process, how does it present in dreams - and lucid dreams - when we are technically asleep?
The sleeping brain is not totally dormant, as scientists assumed for many centuries. When dreaming the brain shows off activity in the theta, alpha and beta ranges (4-31 hertz). But there is no self-awareness present: we don't reflect on who we are, what we're doing, or even the fact that we are dreaming.
In lucid dreaming, however, MRT studies have confirmed that we possess a much higher level of consciousness. We activate more regions of the brain (the right dorsolateral prefrontal cortex, the frontopolar regions and the precuneus). All of these regions are linked with self-reflective functions.
What's more, lucid dreamers have conscious access to their real-world memories during lucid dreaming, whereas regular dreamers do not. The simple recognition of the dreamstate (an act of spontaneous self-awareness in itself) transforms a very basal consciousness to a near waking level of meta-consciousness.
You could therefore argue that the difference between regular dreaming and lucid dreaming is like the difference in self-awareness between a canary and a human. It's a significant leap forward in self-recognition.