What it means if you can see faces in objects - Susan G. Wardle

412,174 views ・ 2023-06-13

TED-Ed


Please double-click on the English subtitles below to play the video.

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Imagine opening a bag of chips only to find Santa Claus looking back at you.
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Or turning the corner to see a smile as wide as a building.
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Humans see faces in all kinds of mundane objects,
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but these faces aren’t real—
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they’re illusions due to a phenomenon known as face pareidolia.
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So why exactly does this happen, and how far can this distortion of reality go?
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Humans are social animals,
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and reading faces is an important part of our ability to understand each other.
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Even a glimpse of someone's face can help you determine if you've met them before,
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what mood they’re in, and if they’re paying attention to you.
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We even use facial features to make snap-judgments
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about a person’s potential trustworthiness or aggression.
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To capture all this vital information,
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humans have evolved to be very sensitive to face-like structures.
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Whenever we see something,
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our brain immediately starts working to identify the new visual stimuli
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based on our expectations and prior knowledge.
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And since faces are so important,
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humans have evolved several regions of the brain
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that enable us to identify them faster than other visual stimuli.
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Whereas recognizing most objects takes our brain around a quarter of a second,
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we can detect a face in just a tenth of a second.
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It makes sense that we'd prioritize identifying faces over everything else.
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But brain imaging studies have revealed that regions
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may actually be too sensitive,
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leading them to find faces where they don’t exist.
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In one study, participants reported seeing illusory faces
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in over 35% of pure-noise images shown to them,
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despite the fact that nothing was there.
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It might seem concerning that our brains can be so wrong so often,
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but these illusory faces might actually be a byproduct
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of something evolutionarily advantageous.
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Since processing all the visual input we encounter quickly and correctly
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is an enormous computational effort for the brain,
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this kind of hypersensitivity might act as a useful shortcut.
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After all, seeing illusory faces is usually harmless,
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while missing a real face can lead to serious issues.
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But for hypersensitivity to be more helpful than harmful,
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our brains also need to be quick at determining when a face is real
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and when it isn’t.
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So how fast can our brains tell when they’ve been duped?
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To answer this question, researchers used a form of brain imaging
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known as magnetoencephalography.
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By measuring the magnetic fields caused by electric currents in the brain,
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this technique allows us to track changes in brain activity
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at the scale of milliseconds.
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With this tool, researchers revealed that the brain generally recognizes
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a face as illusory within a quarter of a second—
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around the same time that we can identify most non-face visual stimuli.
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However, even after our brain knows the face is fake,
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we can still see it in the object.
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And by messing with these brain areas,
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we can further impact our ability to differentiate between fact from fiction.
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In one study, researchers stimulated a participant’s fusiform face area
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while they were looking at a non-face object.
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As a result, the participant reported momentarily seeing facial features
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despite the object remaining unchanged.
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And while looking at a real face, stimulation of this same area
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created perceived distortions of the eyes and nose.
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These studies suggest that certain features are crucial to face detection.
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Just three dots can be enough to represent eyes and a mouth.
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People will even assign gender, age, and emotion to illusory faces.
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It’s unclear whether a person’s culture or individual history
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impacts these perceptions,
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but we do know that pareidolia isn’t unique to the human experience.
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Rhesus macaque monkeys show eye movements similar to our own
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when observing pareidolia-inducing objects and real faces,
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suggesting that this phenomenon is baked deep into our social primate brains.
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So, next time you see an unexpected face in a coffee, car, or cabinet,
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remember that it’s just your brain working overtime
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not to miss the faces that really matter.
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