TedTest

From the Ted Talk by Nathan S. Jacobs: How optical illusions trick your brain

Unscramble the Blue Letters

Check this out: Here's a grid, nothing special, just a basic grid, very grid-y. But look closer, into this white spot at the center where the two central vcraitel and horizontal lines ieenrsctt. Look very closely. ntioce anything funny about this spot? Yeah, nothing. But keep looking. Get weird and stare at it. Now, keeping your gaze fixed on this white spot, check what's happening in your peripheral vision. The other spots, are they still white? Or do they show weird flashes of grey? Now look at this pan for baking mfiufns. Oh, sorry, one of the cups is inverted. It pops up instead of dipping down. Wait, no spin the pan. The other five are domed now? Whichever it is, this pan's defective. Here's a photo of Abraham Lincoln, and here's one upside down. Nothing weird going on here. Wait, turn that upside down one right side up. What have they done to Abe? Those are just three optical illusions, images that seem to trick us. How do they work? Are magical things happening in the iamegs themselves? While we could certainly be siennakg flashes of grey into the peripheral white spots of our animated grid, first off, we promise we aren't. You'll see the same efcfet with a grid printed on a plain old piece of paper. In reality, this grid really is just a grid. But not to your brain's visual system. Here's how it interprets the lhgit information you call this grid. The white intersections are surrounded by relatively more white on all four sides than any white piont along a line segment. Your retinal ganglion cells notice that there is more wthie around the ireeinotntcss because they are organized to isrcanee ctsorant with lateral inhibition. Better contrast menas it's easier to see the edge of something. And things are what your eyes and brain have evolved to see. Your retinal gniolgan cells don't respond as much at the crossings because there is more lateral inhibition for more white stpos nearby cmeopard to the lines, which are surrounded by blcak. This isn't just a defect in your eyes; if you can see, then oaciptl inuloilss can tirck you with your glasses on or with this paper or computer screen right up in your face. What optical illusions show us is the way your photo rropctees and brain assemble visual information into the three-dimensional world you see around you, where egdes should get extra attention because things with edges can help you or kill you. Look at that muffin pan again. You know what causes confusion here? Your brain's visual cortex operates on atsopmsuins about the lighting of this image. It expects light to come from a single source, shining down from above. And so these shading prenttas could only have been caused by light shining down on the sloping sides of a dome, or the bottom of a hole. If we callerfuy recreate these clues by drawing shading patterns, even on a flat piece of ppear, our brain reflexively ceteras the 3D coanvce or convex shape. Now for that ceerpy Lincoln upside down face. Faces trigger activity in areas of the brain that have specifically evolved to help us recognize faces. Like the fusiform face area and others in the oipctcial and tmeaporl lobes. It makes snese, too, we're very social animals with highly cmelpox ways of interacting with each other. When we see faces, we have to recognize they are faces and figure out what they're erxnepssig very quickly. And what we foucs on most are the eyes and mouth. That's how we figure out if someone is mad at us or wants to be our friend. In the upside down Lincoln face, the eyes and mouth were actually right side up, so you didn't notice anything was off. But when we flipped the whole image over, the most important ptras of the face, the eyes and mouth, were now upside down, and you realized something fhisy was up. You realized your brain had taken a short cut and missed something. But your biarn wasn't really being lazy, it's just very busy. So it sdpens cognitive energy as efficiently as possible, using assumptions about visual ionrfmtioan to create a tailored, edited vision of the world. Imagine your brain calling out these edits on the fly: "Okay, those sraeuqs could be objects. Let's enhance that black-white contrast on the sides with lateral inhibition. dearkn those corners! Dark grey fading into light grey? Assume overhead sunlight falling on a sloping curve. Next! Those eyes look like most eyes I've seen before, nothing weird going on here." See? Our visual tricks have revealed your brain's job as a busy director of 3D animation in a studio inside your skull, allocating cognitive energy and constructing a wrlod on the fly with tried and mostly — but not always — true tricks of its own.

Open Cloze

Check this out: Here's a grid, nothing special, just a basic grid, very grid-y. But look closer, into this white spot at the center where the two central ________ and horizontal lines _________. Look very closely. ______ anything funny about this spot? Yeah, nothing. But keep looking. Get weird and stare at it. Now, keeping your gaze fixed on this white spot, check what's happening in your peripheral vision. The other spots, are they still white? Or do they show weird flashes of grey? Now look at this pan for baking _______. Oh, sorry, one of the cups is inverted. It pops up instead of dipping down. Wait, no spin the pan. The other five are domed now? Whichever it is, this pan's defective. Here's a photo of Abraham Lincoln, and here's one upside down. Nothing weird going on here. Wait, turn that upside down one right side up. What have they done to Abe? Those are just three optical illusions, images that seem to trick us. How do they work? Are magical things happening in the ______ themselves? While we could certainly be ________ flashes of grey into the peripheral white spots of our animated grid, first off, we promise we aren't. You'll see the same ______ with a grid printed on a plain old piece of paper. In reality, this grid really is just a grid. But not to your brain's visual system. Here's how it interprets the _____ information you call this grid. The white intersections are surrounded by relatively more white on all four sides than any white _____ along a line segment. Your retinal ganglion cells notice that there is more _____ around the _____________ because they are organized to ________ ________ with lateral inhibition. Better contrast _____ it's easier to see the edge of something. And things are what your eyes and brain have evolved to see. Your retinal ________ cells don't respond as much at the crossings because there is more lateral inhibition for more white _____ nearby ________ to the lines, which are surrounded by _____. This isn't just a defect in your eyes; if you can see, then _______ _________ can _____ you with your glasses on or with this paper or computer screen right up in your face. What optical illusions show us is the way your photo _________ and brain assemble visual information into the three-dimensional world you see around you, where _____ should get extra attention because things with edges can help you or kill you. Look at that muffin pan again. You know what causes confusion here? Your brain's visual cortex operates on ___________ about the lighting of this image. It expects light to come from a single source, shining down from above. And so these shading ________ could only have been caused by light shining down on the sloping sides of a dome, or the bottom of a hole. If we _________ recreate these clues by drawing shading patterns, even on a flat piece of _____, our brain reflexively _______ the 3D _______ or convex shape. Now for that ______ Lincoln upside down face. Faces trigger activity in areas of the brain that have specifically evolved to help us recognize faces. Like the fusiform face area and others in the _________ and ________ lobes. It makes _____, too, we're very social animals with highly _______ ways of interacting with each other. When we see faces, we have to recognize they are faces and figure out what they're __________ very quickly. And what we _____ on most are the eyes and mouth. That's how we figure out if someone is mad at us or wants to be our friend. In the upside down Lincoln face, the eyes and mouth were actually right side up, so you didn't notice anything was off. But when we flipped the whole image over, the most important _____ of the face, the eyes and mouth, were now upside down, and you realized something _____ was up. You realized your brain had taken a short cut and missed something. But your _____ wasn't really being lazy, it's just very busy. So it ______ cognitive energy as efficiently as possible, using assumptions about visual ___________ to create a tailored, edited vision of the world. Imagine your brain calling out these edits on the fly: "Okay, those _______ could be objects. Let's enhance that black-white contrast on the sides with lateral inhibition. ______ those corners! Dark grey fading into light grey? Assume overhead sunlight falling on a sloping curve. Next! Those eyes look like most eyes I've seen before, nothing weird going on here." See? Our visual tricks have revealed your brain's job as a busy director of 3D animation in a studio inside your skull, allocating cognitive energy and constructing a _____ on the fly with tried and mostly — but not always — true tricks of its own.

Solution

receptors
focus
illusions
notice
squares
ganglion
effect
intersections
optical
brain
fishy
sense
edges
compared
spends
muffins
paper
white
vertical
images
information
assumptions
sneaking
patterns
light
complex
increase
world
contrast
occipital
darken
creates
black
parts
temporal
carefully
expressing
intersect
point
means
spots
creepy
trick
concave

Original Text

Check this out: Here's a grid, nothing special, just a basic grid, very grid-y. But look closer, into this white spot at the center where the two central vertical and horizontal lines intersect. Look very closely. Notice anything funny about this spot? Yeah, nothing. But keep looking. Get weird and stare at it. Now, keeping your gaze fixed on this white spot, check what's happening in your peripheral vision. The other spots, are they still white? Or do they show weird flashes of grey? Now look at this pan for baking muffins. Oh, sorry, one of the cups is inverted. It pops up instead of dipping down. Wait, no spin the pan. The other five are domed now? Whichever it is, this pan's defective. Here's a photo of Abraham Lincoln, and here's one upside down. Nothing weird going on here. Wait, turn that upside down one right side up. What have they done to Abe? Those are just three optical illusions, images that seem to trick us. How do they work? Are magical things happening in the images themselves? While we could certainly be sneaking flashes of grey into the peripheral white spots of our animated grid, first off, we promise we aren't. You'll see the same effect with a grid printed on a plain old piece of paper. In reality, this grid really is just a grid. But not to your brain's visual system. Here's how it interprets the light information you call this grid. The white intersections are surrounded by relatively more white on all four sides than any white point along a line segment. Your retinal ganglion cells notice that there is more white around the intersections because they are organized to increase contrast with lateral inhibition. Better contrast means it's easier to see the edge of something. And things are what your eyes and brain have evolved to see. Your retinal ganglion cells don't respond as much at the crossings because there is more lateral inhibition for more white spots nearby compared to the lines, which are surrounded by black. This isn't just a defect in your eyes; if you can see, then optical illusions can trick you with your glasses on or with this paper or computer screen right up in your face. What optical illusions show us is the way your photo receptors and brain assemble visual information into the three-dimensional world you see around you, where edges should get extra attention because things with edges can help you or kill you. Look at that muffin pan again. You know what causes confusion here? Your brain's visual cortex operates on assumptions about the lighting of this image. It expects light to come from a single source, shining down from above. And so these shading patterns could only have been caused by light shining down on the sloping sides of a dome, or the bottom of a hole. If we carefully recreate these clues by drawing shading patterns, even on a flat piece of paper, our brain reflexively creates the 3D concave or convex shape. Now for that creepy Lincoln upside down face. Faces trigger activity in areas of the brain that have specifically evolved to help us recognize faces. Like the fusiform face area and others in the occipital and temporal lobes. It makes sense, too, we're very social animals with highly complex ways of interacting with each other. When we see faces, we have to recognize they are faces and figure out what they're expressing very quickly. And what we focus on most are the eyes and mouth. That's how we figure out if someone is mad at us or wants to be our friend. In the upside down Lincoln face, the eyes and mouth were actually right side up, so you didn't notice anything was off. But when we flipped the whole image over, the most important parts of the face, the eyes and mouth, were now upside down, and you realized something fishy was up. You realized your brain had taken a short cut and missed something. But your brain wasn't really being lazy, it's just very busy. So it spends cognitive energy as efficiently as possible, using assumptions about visual information to create a tailored, edited vision of the world. Imagine your brain calling out these edits on the fly: "Okay, those squares could be objects. Let's enhance that black-white contrast on the sides with lateral inhibition. Darken those corners! Dark grey fading into light grey? Assume overhead sunlight falling on a sloping curve. Next! Those eyes look like most eyes I've seen before, nothing weird going on here." See? Our visual tricks have revealed your brain's job as a busy director of 3D animation in a studio inside your skull, allocating cognitive energy and constructing a world on the fly with tried and mostly — but not always — true tricks of its own.

Frequently Occurring Word Combinations

ngrams of length 2

collocation	frequency
lateral inhibition	3
white spots	2
retinal ganglion	2
ganglion cells	2
optical illusions	2
visual information	2
cognitive energy	2

ngrams of length 3

collocation	frequency
retinal ganglion cells	2

Important Words

abe
abraham
activity
allocating
animals
animated
animation
area
areas
assemble
assume
assumptions
attention
baking
basic
black
bottom
brain
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calling
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create
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curve
cut
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director
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drawing
easier
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edited
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effect
efficiently
energy
enhance
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expressing
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face
faces
fading
falling
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flat
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fly
focus
friend
funny
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kill
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lazy
light
lighting
lincoln
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mad
magical
means
missed
mouth
muffin
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objects
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optical
organized
overhead
pan
paper
parts
patterns
peripheral
photo
piece
plain
point
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printed
promise
quickly
reality
realized
receptors
recognize
recreate
reflexively
respond
retinal
revealed
screen
segment
sense
shading
shape
shining
short
show
side
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single
skull
sloping
sneaking
social
source
special
specifically
spends
spin
spot
spots
squares
stare
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sunlight
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tailored
temporal
trick
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trigger
true
turn
upside
vertical
vision
visual
wait
ways
weird
white
work
world
yeah