Take a look at this. What do you see? Do you see wide-eyed wolf snarling at you or a two-headed angel with its wings spread out? Maybe Krusty the Clown looking at himself in the mirror. Now look at this. If you're like most people, you probably see a bunch of rock, but if you're the internet, then you see proof that tiny alien fairies are walking around on Mars.
 
The first picture I showed you was a kind of psychological exercise, I'm sure you've heard of it, a Rorschach test. Nearly a hundred years ago, Swiss psychiatrist Hermann Rorschach came up with this method to get insights into his patients' personalities. He showed his patients random symmetrical ink patterns and asked them to describe what they saw. Rorschach thought that like if a patient described screaming faces all the time that could be a sign of anti-social tendencies or anxiety. Sounds pretty subjective, and it was which is why it's not used in psychology much any more.

But the second picture that I showed you is not random or abstract or part of a psychological test, at least not an intentional one. It's one of the thousands of images that have been sent to Earth by the Curiosity rover on Mars, and over the past couple of weeks a small but noisy corner of the internet has been fixated on what it thinks is a woman in this picture. You see it? Let's zoom in. Anything there? Yeah. That's it apparently.

Now I won't waste your time by explaining why after more than a century of observations and 7 working spacecrafts sent to its surface we know that there are not little nymphs hopping around on Mars. But I do want to tell you why people keep seeing all kinds of crazy stuff there, because this lady is only the latest weird manifestation to supposedly appear in pictures from Curiosity. Just this summer alone, the media have been replete with reports of people seeing a crab, an alien's head, and a pyramid on the surface of Mars. And if you remember that giant face on Mars back in the 80's and 90's you know that none of this is new.

The fact is both the wolf in the inkblot and the woman on Mars are the result of the same psychological phenomenon. It's known as pareidolia - the tendency humans have to perceive familiar images, especially faces, where none exist. Pareidolia happens to everyone and unlike a hallucination, it manifests itself as something we see in something else, like seeing Pepe the frog in a piece of toast. Scientists have known about this phenomenon for centuries but they've only recently begun to figure out exactly how it happens. 

Last year, a team of Chinese and Canadian researchers wanted to test the incidents of two different kinds of pareidolia, one in which people specifically see faces and another where they see letters and words. The researchers showed participants images that were pure, visual static but they told the subjects that half of the pictures contained either faces or letters. Even though the pictures were pure gibberish, more than a third of the subjects reported they distinctly saw something, 34% said they saw faces and 38% said letters. And brain scans conducted during the test showed that in the people who reported seeing faces, brain activity spiked in what's known as the right fusiform face area - the region that's activated when we try to recognize someone's face.

Why's that important? Well, because those people weren't seeing faces, they were just told that they might be by the scientists. So this suggests that instead of being first triggered by a simple external stimulus like an image of a human face, pareidolia automatically happens in the higher, more complex functions of the brain where the brain already thinks it's seeing a face and is trying to figure out who it is. And the phenomenon turns out to be much more common in people who believe in things they can't see. 

In another experiment in Finland in 2012, 47 people were shown dozens of pictures of everyday objects, some of which were altered so that they did have faintly face-like features. The subjects were then interviewed about their personal beliefs like whether they were religious or believed in ghosts and the paranormal, or whether they were atheists or skeptics. The results showed that people who believed in the supernatural were better at finding faces in the pictures, but they were also more likely to see faces that weren't there and even assigned certain emotions to them. 

So some of this may explain why some of the most popular instances of pareidolia have involved religious imagery, like when people saw the face of Jesus in a tortilla in Mexico, or when a cinnamon bun bore the likeness to many of Mother Teresa. And by most standards, thinking that there are fairies on Mars would qualify as believing in the paranormal. 

Humans are perceptive creatures. We've learned over the eons to see patterns, especially each other, with ease even at great distances and in near darkness. So those pictures coming from Mars are not proof of little women living on Mars but they are reminders of our own evolutionary development. 

Thank you to the viewers who asked us to explain the science behind the woman on Mars. If you have questions about topics in the news that you'd like to understand better you can let us know and if you want to keep getting smarter with us you can go to youtube.com/scishow and subscribe.