Above: Do you see a face in that electric socket?
Image © michaeljmc,iStockPhoto.com
Congratulations! You are a face expert.
Are you wondering what you did to deserve this title? Then you’ll be surprised to know that you’ve really been a face-expert-in-training your entire life.
Faces are one of the most common classes of visual object that people see. The more you see objects, the more visual expertise you gain with them. In fact, people have so much face expertise that our brains see faces even when they probably shouldn’t. That’s why you see power outlets that look like they’re frowning, happy car fronts, and faces on the surface of Mars.
These are examples of pareidolia, seeing patterns that don’t exist. Pareidolia happens especially often for faces simply because of the way that our brains are wired.
Did you know? In 2004, a customer on eBay spend $28,000 USD on a grilled cheese sandwich that appeared to have the Virgin Mary’s face in it!
How does your brain process faces?
Your brain processes most of the objects you see, like cars or houses, with the lateral occipital complex (LOC). That’s a brain region located in the outward portion of the occipital lobe, a region of the brain at the back of the head. Faces, however, seem to have their a region of the brain dedicated to recognizing them. It’s called the fusiform face area (FFA). There is a whole network of brain areas involved in face perception, but we’re going to focus on the FFA here.
The LOC and FFA are pretty close to each other in the brain, but they process stimuli quite differently. The LOC processes objects in a part-based manner, while the FFA uses holistic processing. To understand the difference between these two processing types, take a look at one of Giuseppe Arcimboldo's famous paintings below.
We perceive objects and faces as a whole image. But that’s not how they are first represented in your brain. If you were looking at this image in a part-based manner, you’d see a lot of individual pieces of fruit. That’s how the LOC represents faces and objects: on a part by part basis.
On the other hand, if you look at the whole image, or the holistic version of this image, you can see that the fruit makes up a face. That’s how the FFA works, by representing the relationships between the parts that make up the face.
For example, in the painting above, you can see that the pear is the nose and the apple slice is the ear because they are in the correct spatial position relative to each other. It’s these spatial relationships between the face parts that let us identify people by face.
The Expert Brain
The name “fusiform face area” is actually a little misleading. Processing faces is the FFA’s main job, but not its only one. Remember how I said that you were a face expert? Well, the FFA processes types of objects that you have visual expertise with. For example, in one study, researchers used an MRI scanner to look at what happened in people’s brains when they looked at pictures of birds and cars. Study participants who did a lot of bird watching used their FFA more than their LOC in response to the bird pictures. And while the LOC would be the main area involved in processing cars in most people, car experts used more of their FFA in response to cars.
One group of researchers was even able to train participants to gain visual expertise with made-up creatures called “greebles”. As the participants got better at identifying greebles, they began to use their FFA more when looking at them. Why does this shift to the FFA happen when a person gains experience? Well, scientists think the FFA is probably really good at discriminating different members of an object category, like different species of birds, types of cars, or specific people.
Did you know? Lesions to the fusiform face area in the brain can result in prosopagnosia, or face blindness, which is an inability to recognize individuals’ faces.
Summing up with an illusion
Faces are pretty special! Our brains are so used to seeing them that we process them differently from most other types of objects. The use of holistic processing in the FFA instead of part-based processing in the LOC lets us recognize faces quickly and accurately, despite a few small slip-ups every now and again.
I’m going to leave you below with a famous illusion demonstrating the power of holistic processing. Check out these upside-down faces:
Above: Image © Hannah DePriest, Pexels Modified by Sarah McCrackin
Your brain processes upside-down faces in a part-based manner because you’re not used to seeing faces in that orientation. Since each picture has two eyes, a mouth, and a nose, the pictures look okay when you’re using part-based processing. Now let’s flip the same images right side up, so that you switch back to holistic processing:
Above: Image © Hannah DePriest, Pexel Modified by Sarah McCrackin
In the two pictures above, your FFA is hard at work processing the relationship between the parts of the face. Now it’s immediately clear that the parts aren’t oriented how they should be in relation to each other. The difference is immediate – and even a little terrifying!
This phenomenon is known as the Thatcher Illusion. That’s because a British professor first used photos of former British Prime Minister Margaret Thatcher to explain it. You can have some fun with the Thatcher Illusion at this link!
Did you know? A more modern version of the Thatcher Illusion hit Instagram in 2016, when Adele’s face was shown upside down and photoshopped so that her eyes and mouth were the only parts right-side up. Since our brains process upside down and right-side up faces differently, no one could see anything wrong with the picture...that is, until they flipped their phones upside down!
The Thatcher illusion: Are faces special? (2016)
Etchells, The Guardian.
Seeing Jesus in toast: Neural and behavioral correlates of face pareidolia (2014)
Liu et al., Cortex 53.
The fusiform face area: a cortical region specialized for the perception of faces (2006)
Kanwisher & G. Yovel, Philos Trans R Soc Lond B Biol Sci. 361.