full transcript

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

Unscramble the Blue Letters

cchek this out: Here's a grid, nothing special, just a basic grid, very grid-y. But look closer, into this white spot at the ctneer where the two central vetciral 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 bkniag muffins. Oh, sorry, one of the cups is inverted. It pops up instead of dppiing 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 opitacl illusions, imgaes that seem to ticrk 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 eefcft 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 vsuail 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 withe point along a line segment. Your retinal ganglion cells nticoe that there is more white around the intcnroteises because they are organized to increase contrast with lateral itohibiinn. 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 suodnuerrd 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 cometpur screen right up in your face. What optical illnisous 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 atttoeinn because things with edges can help you or kill you. Look at that muffin pan again. You know what causes cuoinofsn here? Your brain's visual cortex operates on assumptions about the lighting of this igame. 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 peapr, our brain reflexively creates the 3D cvnacoe or ceovnx spahe. Now for that creepy Lincoln upside down face. Faces trigger activity in areas of the brain that have sacpiflecliy evolved to help us recognize faces. Like the fusiform face area and others in the ociptcial and temporal loebs. It makes sense, too, we're very siocal animals with highly complex ways of itcnaeintrg 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 fenird. In the upside down llcnion face, the eyes and mtuoh 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 reaezild your brain had taken a sorht cut and missed something. But your brain wasn't really being lazy, it's just very busy. So it spends cognitive energy as enticeflfiy as possible, using amtsuniposs about visual information to create a tailored, etdied vision of the world. Imagine your biran calling out these etdis on the fly: "Okay, those suqares could be oetcjbs. 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, allaocintg cognitive energy and ccurotnnitsg a world on the fly with tried and mostly — but not always — true tricks of its own.

Open Cloze

_____ this out: Here's a grid, nothing special, just a basic grid, very grid-y. But look closer, into this white spot at the ______ where the two central ________ 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 ______ muffins. Oh, sorry, one of the cups is inverted. It pops up instead of _______ 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 _______ illusions, ______ that seem to _____ 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 ______ 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 ______ 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 _____ point along a line segment. Your retinal ganglion cells ______ that there is more white around the _____________ because they are organized to increase contrast with lateral __________. 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 __________ 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 ________ screen right up in your face. What optical _________ 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 _________ because things with edges can help you or kill you. Look at that muffin pan again. You know what causes _________ here? Your brain's visual cortex operates on assumptions about the lighting of this _____. 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 _____, our brain reflexively creates the 3D _______ or ______ _____. Now for that creepy Lincoln upside down face. Faces trigger activity in areas of the brain that have ____________ evolved to help us recognize faces. Like the fusiform face area and others in the _________ and temporal _____. It makes sense, too, we're very ______ animals with highly complex ways of ___________ 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 ______. In the upside down _______ face, the eyes and _____ 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 ________ your brain had taken a _____ cut and missed something. But your brain wasn't really being lazy, it's just very busy. So it spends cognitive energy as ___________ as possible, using ___________ about visual information to create a tailored, ______ vision of the world. Imagine your _____ calling out these _____ on the fly: "Okay, those _______ could be _______. 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, __________ cognitive energy and ____________ a world on the fly with tried and mostly — but not always — true tricks of its own.

Solution

  1. center
  2. convex
  3. attention
  4. visual
  5. computer
  6. effect
  7. specifically
  8. paper
  9. inhibition
  10. friend
  11. realized
  12. illusions
  13. lobes
  14. white
  15. dipping
  16. brain
  17. short
  18. social
  19. lincoln
  20. mouth
  21. edited
  22. concave
  23. objects
  24. constructing
  25. baking
  26. notice
  27. occipital
  28. allocating
  29. interacting
  30. assumptions
  31. squares
  32. trick
  33. optical
  34. surrounded
  35. images
  36. intersections
  37. confusion
  38. efficiently
  39. edits
  40. vertical
  41. check
  42. image
  43. shape

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

  1. abe
  2. abraham
  3. activity
  4. allocating
  5. animals
  6. animated
  7. animation
  8. area
  9. areas
  10. assemble
  11. assume
  12. assumptions
  13. attention
  14. baking
  15. basic
  16. black
  17. bottom
  18. brain
  19. busy
  20. call
  21. calling
  22. carefully
  23. caused
  24. cells
  25. center
  26. central
  27. check
  28. closely
  29. closer
  30. clues
  31. cognitive
  32. compared
  33. complex
  34. computer
  35. concave
  36. confusion
  37. constructing
  38. contrast
  39. convex
  40. cortex
  41. create
  42. creates
  43. creepy
  44. crossings
  45. cups
  46. curve
  47. cut
  48. dark
  49. darken
  50. defect
  51. defective
  52. dipping
  53. director
  54. dome
  55. domed
  56. drawing
  57. easier
  58. edge
  59. edges
  60. edited
  61. edits
  62. effect
  63. efficiently
  64. energy
  65. enhance
  66. evolved
  67. expects
  68. expressing
  69. extra
  70. eyes
  71. face
  72. faces
  73. fading
  74. falling
  75. figure
  76. fishy
  77. fixed
  78. flashes
  79. flat
  80. flipped
  81. fly
  82. focus
  83. friend
  84. funny
  85. fusiform
  86. ganglion
  87. gaze
  88. glasses
  89. grey
  90. grid
  91. happening
  92. highly
  93. hole
  94. horizontal
  95. illusions
  96. image
  97. images
  98. imagine
  99. important
  100. increase
  101. information
  102. inhibition
  103. interacting
  104. interprets
  105. intersect
  106. intersections
  107. inverted
  108. job
  109. keeping
  110. kill
  111. lateral
  112. lazy
  113. light
  114. lighting
  115. lincoln
  116. line
  117. lines
  118. lobes
  119. mad
  120. magical
  121. means
  122. missed
  123. mouth
  124. muffin
  125. muffins
  126. nearby
  127. notice
  128. objects
  129. occipital
  130. operates
  131. optical
  132. organized
  133. overhead
  134. pan
  135. paper
  136. parts
  137. patterns
  138. peripheral
  139. photo
  140. piece
  141. plain
  142. point
  143. pops
  144. printed
  145. promise
  146. quickly
  147. reality
  148. realized
  149. receptors
  150. recognize
  151. recreate
  152. reflexively
  153. respond
  154. retinal
  155. revealed
  156. screen
  157. segment
  158. sense
  159. shading
  160. shape
  161. shining
  162. short
  163. show
  164. side
  165. sides
  166. single
  167. skull
  168. sloping
  169. sneaking
  170. social
  171. source
  172. special
  173. specifically
  174. spends
  175. spin
  176. spot
  177. spots
  178. squares
  179. stare
  180. studio
  181. sunlight
  182. surrounded
  183. system
  184. tailored
  185. temporal
  186. trick
  187. tricks
  188. trigger
  189. true
  190. turn
  191. upside
  192. vertical
  193. vision
  194. visual
  195. wait
  196. ways
  197. weird
  198. white
  199. work
  200. world
  201. yeah