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The mirror test is supposed to be a way to figure out when an animal is self-aware, but there might be only one particular animal this test works well on: humans.

Check out the episode about fish intelligence over on the main SciShow channel:

Hosted by: Brit Garner & Stefan Chin
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[INTRO ♪] [approaching footsteps] >>

Brit: Hey, Stefan. What's up? >>

Stefan: Hey! Just making sure I'm ready for the shoot. >>

Brit: Oh, that's actually a good idea! Let me... >>

Brit: Did you ... did you put a sticker on my head? >>

Stefan: No. Well, yes, I did. >>

Stefan: I was reading about this fish that passed a mirror test recently, and I wanted to kinda see that in action. >>

Brit: Okay, well, of course I passed it! >>

Brit: But have you those videos of puppies that are playing with their reflections like it's another dog? >>

Stefan: [sigh] I love those videos. >>

Brit: Well, that's what it looks like when you don't pass the mirror test. Basically, the mirror test is all about whether or not you recognize yourself in the mirror. It's a tool psychologists have used since the 1970s to study whether or not animals are self-aware… and for a long time, they thought that self-awareness said something bigger about an animal's' intelligence. >>

Brit: So humans and apes? Smart! >>

Brit: That puppy barking at a reflection? Not so much. >>

Brit: But as more and more animals pass the test, there are also more questions about whether or not the test ever really mattered in the first place. >>

Brit: There's a lot to talk about here, so I was thinking that since we borrowed you from the main SciShow channel today, you could help me explain what the test is all about. >>

Stefan: Yeah! Let's do it! >>

Brit: So here's how the mirror test works. Once an animal has had some time to get used to having a mirror around, a researcher sneakily paints a colored dot somewhere that the animal can only see with the help of the mirror. The moment of truth comes when the animal looks back in the mirror. Do they notice the dot and then touch or try to remove the corresponding spot on their own body?

If so, it suggests that they realize the animal in the mirror is a reflection of themselves. >>

Stefan: The test was first proposed by a researcher in 1970, and he used it to study chimps. At first, his subjects reacted as if the chimp in the mirror was somebody else but with time they got the hang of it. They started grooming places they wouldn't be able to see without the mirror and picking food out of their teeth. The researcher added the test with the colored dot mostly just to confirm experimentally that the chimps did recognize themselves—and they did!

And over the next decade, researchers found that orangutans and chimps consistently passed the mirror test, but monkeys did not. This led them to argue that the mirror test indicated an intellectual distinction separating humans and the great apes, which are our closest relatives, from the rest of the primates… and presumably the rest of the animal kingdom. >>

Brit: Yup! Psychologists believed that the animals that passed the test had a sense of self. Basically, they knew that they existed—which isn't totally off base, if you look at humans. Human babies only start to pass the mirror test around 18 months of age.

And shortly after they do, they start to be able to do all sorts of other sense-of-self-type things. They understand that other people have their own thoughts and feelings. They experience so-called secondary emotions, like embarrassment, pride, and guilt, which require knowing you did something right or wrong.

Psychologists theorize that the sense of self is really important for both understanding the concept of other people having selves and for imagining yourself in other scenarios—past, future, and hypothetical. That allows us to plan and remember, which supposedly makes us pretty unique. >>

Stefan: But then… other species started to pass the test. In 1998, bottlenose dolphins became the first non-primates to pass the mirror test. While they obviously don't have hands to try to wipe the mark off with, they did twist and turn to try to see it. Then orcas passed, too, and in 2006, an Asian elephant named Happy passed the test, although her companions Maxine and Patty failed.

Still, you might say elephants and dolphins are animals we all kind of expect to be pretty smart, so those results aren't necessarily surprising. But then magpies became the first birds to pass the test in 2008. These birds do belong to the corvid family, and corvids are clever birds, but it still surprised many researchers.

And more surprises followed—like ants. You probably don't often think of those picnic-invading, hive-minded insects as individuals with a sense of self, but they were curious about their reflections and tried to rub off a blue dot when they saw it in the mirror. And then, most recently, researchers found that a kind of fish called a cleaner wrasse will swim upside down and in funny positions in front of a mirror to try to see a dot on itself when it's marked, making it the first fish to formally pass the test.

We have a whole episode about fish intelligence over on the main SciShow channel, and they're pretty smart! But even the researcher who wrote the 2018 study about the cleaner wrasse was quick to point out that this doesn't mean they have the same level or type of intelligence as humans. >>

Brit: With every non-human animal that passes the test, the story around it gets… messier. Some researchers, including the guy who came up with the test, continue to argue that these non-human animals aren't actually passing it. Only one in three elephants passed, after all, and does the cleaner wrasse swimming upside down actually mean anything? But the arguments against the test are also building.

There are methodological differences in how these studies were conducted, and many of them tested just a few individuals. It also might be kind of silly to use a sight-dependent test on species that are known to rely on other senses— the way that elephants and, yes, adorable puppies rely on smell. Elephants also groom themselves by chucking dirt on themselves, so expecting them to remove a colorful speck of researcher-applied dirt might be unreasonable. >>

Stefan: The test is also just weirdly unreliable. Gorillas, despite being great apes, don't pass it, but eye contact is extremely aggressive for them, and studies have shown that they're easily embarrassed. So they might literally be so self-conscious that they fail our test of self-consciousness. Also… humans don't always pass it.

Kids as old as six from non-Western cultures sometimes don't, despite the fact that there are usually mirrors where they're from and they obviously have a sense of self. And although monkeys have traditionally failed, one researcher found that after being around mirrors for a lot of their lives, the monkeys she studied did start to use them to groom places they couldn't see. They just needed more time to learn how to use them. >>

Brit: All of these inconsistencies are leading researchers to consider a different explanation:. Maybe there just... isn't some weird hierarchy of brilliance. The irony of the mirror test is that our obsession with it might say more about the limits of our own cognition than it does about any other species. Because we designed a test that we—as a visually-oriented, social species obsessed with grooming—would pass ... and then we used to it judge everybody else.

And, you know, is there anything more human than that? >>

Brit: Thanks for watching this episode of SciShow Psych! And thanks to Stefan, for helping me break down the mirror test. >>

Stefan: If you want to learn more about fish brains and all the other smart things they can do, you can check out an episode that we did on the main SciShow channel about fish intelligence. >>

Brit: And you can see more of Stefan and learn about all kinds of science by subscribing to the channel while you're over there! [OUTRO ♪].