The mirror test—sometimes called the mark test, mirror self-recognition (MSR) test, red spot technique, or rouge test—is a behavioural technique developed in 1970 by American psychologist Gordon Gallup Jr. as an attempt to determine whether an animal possesses the ability of visual self-recognition.The MSR test is the traditional method for attempting to measure self-awareness. However, agreement has been reached that animals can be self-aware in ways not measured by the mirror test, such as distinguishing between their own and others' songs and scents. Conversely, animals that can pass the MSR do not necessarily have self-awareness.
In the classic MSR test, an animal is anaesthetised and then marked (e.g., painted or a sticker attached) on an area of the body the animal cannot normally see. When the animal recovers from the anaesthetic, it is given access to a mirror. If the animal then touches or investigates the mark, it is taken as an indication that the animal perceives the reflected image as itself, rather than of another animal.
WHAT ANIMALS CAN RECOGNIZE THEMSELVES :
Asian elephants display a wide range of reactionary behaviors when they see their reflections in mirrors, and will respond to colored markings placed in-view on their bodies. However, not all of the elephants in a study2 by Joshua M. Plotnik passed. This might be because the normal behavior of elephants conflicts with what passing the mirror test requires. “
The mark test can be difficult to apply across species because it assumes that a particular animal will be interested in something weird on their body. Primates are interested in such things—we’re groomers. But elephants are different. They’re huge and they’re used to putting things on, not taking things off of their bodies, like mud and dirt.” said Plotnik.3
The Great Apes
Bonobos, chimpanzees, orangutans, and gorillas have all passed the mirror test.4,1,5 However, it isn’t uncommon for many individuals to fail, especially if they are particularly young or old. In chimpanzees, there is evidence for self-recognition in about 75% of young adults.6 This percentage lowers with individuals closer to either end of the age spectrum.
Many gorillas have failed the mirror test. When shown a mirror, a number of silverbacks have exhibited aggressive behavior. It has been speculated that most of the gorillas and other primates who do not pass the test may have inhibited behavior due to the presence of observing humans.
“Ironically, it may have been the gorillas’ very capacity for self-consciousness that prevented them from exhibiting behaviours indicative of self-recognition in the test situation.”7
Additionally, gorillas will often avoid eye contact with their reflection. By avoiding eye contact, gorillas are likely not able to look at their reflection long enough to realize that it is themselves who they are seeing. Koko the gorilla, well known for having learned sign language and performing well in other cognitive experiments, was the first of her species to pass the test.
Bottlenose dolphins usually show extreme interest when they catch sight of their reflections. They will open their mouths, stick out their tongues, and make a series of novel movements while observing themselves in the mirror. When marked, dolphins regularly inspect the marking.8
In a study9, orca whales were allowed to view themselves in a mirror. Afterward, they were marked, then allowed to view themselves in the mirror once more. Their behavior showed that they expected the image would be altered as a result of their being marked – a strong indication that they understand the image in the mirror is indeed of themselves.
The Eurasian magpie is the first non-mammalian species to pass the mirror test.10 When contrasting colored stickers were placed on their feathers, the magpies reacted to their reflections by trying to remove the mark. Birds who were marked with invisible stickers showed no altered behavior.
Prior to this experiment, scientists believed that self-recognition abilities came from the neocortex, a part of the brain found only in mammals. Since magpies are birds, they do not have this part of the brain. Magpies passing the mirror test shows that the ability of self-recognition can arise from different brain parts in other types of brains. It’s a case of “convergent evolution”. This happens when similar abilities, behaviors, and traits independently evolve in species that are not closely related.
In 2015, scientists published research11 that suggests some ants can recognize themselves when looking in a mirror. When viewing other ants through glass, ants didn’t divert from their normal behaviors.
However, their behavior did change when they were put in front of a mirror. The ants would move slowly, turn their heads back and forth, shake their antennae, and touch the mirror. They’d retreat and re-approach the mirror. Sometimes they would groom themselves.
The ants were next given a classic mirror test. The team of researchers would use blue dots to mark the clypeus of some of the ants, which is a part of their face near their mouths.
When in an environment without mirrors, these ants would behave normally, and wouldn’t touch the markings. But this changed when they could see their reflections in a mirror. The ants with blue dots on their face would groom and appear to try to remove the markings.
Very young ants, and other ants with brown dots that blended in with the color of their face didn’t clean themselves. Interestingly, neither did ants with blue dots put on the back of their heads.
When put in the company of those with blue-dotted faces, other ants would respond aggressively, presumably because the difference caused them to think the blue-dotted ant was an outsider (not a member of their colony). All of this lead the researchers to conclude that the clypeus is a species-specific physical characteristic that is important for group acceptance.
Given that these ants tried to clean the mark rather than respond aggressively, the ants likely didn’t think their reflection was just another ant. The team thinks their study shows that self-recognition is not an “unrealistic” ability in ants.
Promising Candidates: Manta Rays
When it comes to fish, manta rays have the largest brains. This fact lead Dr. Csilla Ari to suspect that they might be the fish species most likely to pass the mirror test.12, 13 When she exposed captive manta rays to a large mirror, they showed great interest in their reflections.
The rays would repeatedly swim in front of the mirror, turning over to show their undersides and moving their fins. When in front of the mirror, they even blew bubbles, an unusual behavior. What the rays didn’t do is try to socially interact with the mirror image.
All of this suggests that the rays might recognize it’s themselves they’re seeing in the mirror, not another ray. However, a classic mirror test using marks on the rays’ bodies has yet to be done. If rays can pass a mark test, it’s a more solid indication of self-recognition abilities. The presence of exploratory behavior and a lack of social behavior doesn’t automatically indicate self-recognition.