Do you see a face in that electric socket? (michaeljmc,
iStockPhoto) Do you see a face in that electric socket? (michaeljmc, iStockPhoto) Learn how your brain recognizes faces and why you sometimes see them in
places they don’t exist! Congratulations! You are a face expert. You’ve been training for it your entire life. Faces are some of the most common things we see. The more you see certain things, the more visual experience you gain with them. In fact, people are such experts with faces that our brains see faces even when they shouldn’t. That’s why you might see power outlets that look like they’re frowning, cars
that look happy, or even faces on the surface of Mars. These are examples of pareidolia. This means seeing patterns where they don’t exist. Pareidolia happens a lot for faces because of how our brains are wired.
How does your brain process what it sees?Your brain can only make sense of what your eyes tell it. But this communication is more complex than you’d think. Light goes into your eyes and hits a light-sensitive surface at the back. This is called the retina. The retina captures an image of what you’re looking at using photoreceptors. But the image your brain sees is upside down! Your eye is convex, or curved outward. When light hits a convex object, it refracts. This flips the image upside-down. You also have a blind spot. That’s the point where the optic nerve (which goes to the brain) connects to the retina. It has no photoreceptors at all. But you don’t see the world upside-down, or with a hole in the middle of it. Your brain knows it always gets images upside down, so it flips all the information automatically. And when light hits the blind spot in one eye, your brain uses information from your other eye to fill in the gap. What you see, in other words, is not always what your eyes are telling your brain. Your brain is always interpreting the information it gets, to give you the best picture. But sometimes it can be fooled. Test your blind spot with this tool from Let's Talk ScienceSeeing faces where there aren’t anyYour brain processes most of the objects you see, like cars or houses, with the lateral occipital complex (LOC). The LOC is a part of the brain located in the outward portion of the occipital lobe. The occipital lobe is located near the back of the head. But faces seem to have a whole region of the brain dedicated to recognizing them. This is 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. Location of the Fusiform Face Areas and Lateral Occipital Complexes (© 2020 Let’s Talk Science using an image by VectorMine via iStockphoto).The LOC and FFA are close to each other in the brain, but they deal with information very differently. The LOC thinks about objects in terms of their parts (part-based processing). The FFA thinks about objects as a whole (holistic processing). To
understand the difference between these ways of processing information, take a look at the famous Giuseppe Arcimboldo painting below.
But if you look at the painting as a whole, or in a holistic way, you can see that the fruit and vegetables make up a face. That’s how the FFA works — by processing the relationships between the parts that make up the face. In the painting, you can tell that the pear is the nose and the mushroom is the ear. This is because they are in the correct positions to stand in for these parts of the face. You can see this when you compare the pear and mushroom with each other, and with all the other fruits and vegetables that make up the face. It is understanding these spatial relationships that lets us identify people, just by looking at their faces. The Expert BrainThe name “fusiform face area” is actually a little misleading. Processing faces is the FFA’s main job, but it does other work as well. Remember how I said that you were a face expert? Well, the FFA processes any type of object that you have visual expertise with. For example, in one study, researchers used an fMRI scanner to see what happened in people’s brains when they looked at pictures of birds and cars. People who did a lot of bird watching used their FFAs more than their LOCs when they saw bird pictures. With pictures of cars, most people used mainly their LOCs. But car experts used more of their FFAs when they saw cars. One group of researchers was even able to teach people visual expertise with made-up creatures they called “greebles”. As people got better at identifying greebles, they began to use their FFAs more when they looked at them. Three of the greebles (Source: Scott Yu, I. Gauthier, I., M.J. Tarr [GFDL 1.3] via Wikimedia Commons).Why do people use their FFAs more when they have more experience looking at an object? Well, scientists think the FFA is probably really good at telling the difference between members of the same object category. Like different species of birds, different types of cars, or individual humans for example.
Summing up with an illusionFaces are pretty special! Our brains are so used to seeing them that we process them differently from most other types of objects. Holistic processing in the fusiform face area of our brains lets us recognize faces quickly and accurately. Even if we do slip up once and awhile! I’m going to leave with a famous illusion that shows us the power of holistic processing. Check out these upside-down faces: Upside-down images of former British Prime Minister Margaret Thatcher (Source: Photography: Rob Bogaerts; Image manipulation: Phonebox [CC0] via Wikimedia Commons).
The difference is immediate, and even a little terrifying! In the upside down pictures, your FFA was hard at work trying to make sense of the relationships between the different parts of each face. Now that they are right side up, it’s clear that eyes and mouth on the right-hand photograph have been flipped. This 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 on this website!
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Learn moreReferencesGauthier, I. & Tarr, M. J. (1997). Becoming a “Greeble” expert: Exploring mechanisms for face recognition. Vision Research, 37(12), 1673–1682. DOI: 10.1016/s0042-6989(96)00286-6 Gauthier, I., Tarr, M. J., Anderson, A. W., Skudlarski, P., & Gore, J. C. (1999). Activation of the middle fusiform “face area” increases with expertise in recognizing novel objects. Nature Neuroscience, 2(6), 568–573. DOI: 10.1038/9224 Gauthier, I., Skudlarski, P., Gore, J. C., & Anderson, A. W. (2000). Expertise for cars and birds recruits brain areas involved in face recognition. Nature Neuroscience, 3(2), 191–197. DOI: 10.1038/72140 Kanwisher, N., & Yovel, G. (2006). The fusiform face area: A cortical region specialized for the perception of faces. Philosophical Transactions of the Royal Society B: Biological Sciences, 361(1476), 2109–2128. DOI: 10.1098/rstb.2006.1934 Liu, J., Li, J., Feng, L., Li, L., Tian, J., & Lee, K. (2014). Seeing Jesus in toast: Neural and behavioral correlates of face pareidolia. Cortex, 53, 60–77. DOI: 10.1016/j.cortex.2014.01.013 Thompson, P. (1980). Margaret Thatcher: A new illusion. Perception, 9(4), 483–484. DOI: 10.1068/p090483 |