52. The Dress Illusion What is the color of the dress you see in the image to the right? • gold on top with white below • dark brown on top with blue below This is the actual dress. The original picture was highly overexposed and shadows vanish. Our visual system has too little information to guess at the direction and color of the illumination and ambient lighting. It guesses and in different people, the guess will differ. When this picture was shown on the Internet in 2015, it went viral with close to a million views per minute. There was nowhere near a consensus as to the actual colors of the dress. www.mastermathmentor.com

53. The Strawberry Illusion When a mask is placed over the tart, showing what seems to be the reddest parts of the strawberry, all the red disappears. There is no red in the picture at all. Not one pizel! Shown to the right is an image of a strawberry tart. The image has a bluish haze over it. What color are the strawberries? This is a complex illusion having to do with how the brain interprets colors. However, a simple explanation is that since we expect to see strawberries as red, that expectancy affects color perception to a degree. www.mastermathmentor.com

54. The Curvature Blindness Illusion If that is what you see, then you have a case of curvature blindness. Because every set of lines in the image are wavy! It is not quite understood why the illusion works but Takahashi believes that because of the gently and shallow slopes and the grey background, the brain doesn’t know for sure whether it is seeing a curve or an angle and interprets them as corners. Shown to the right is an image created by Kohske Takahasi in 2017. If you look at the areas with the white background and black background in the top left and bottom right, you will see pairs of wavy lines. However in the area in the middle with the grey background, you see alternating pairs of zig-zag lines and wavy lines. www.mastermathmentor.com

55. The Venetian Mask Illusion Actually there are two distinct faces – a man and a woman kissing one another. Shown to the right is an image created in 2011 by Gianni Sarcone, Courtney Smith, and Marie-Jo Waeber. The image contains a mask over a slightly blurred face. Keep looking. See anything else? Once the viewer discerns two individual faces, his/her brain will flip between two possible interpretations of the mask, making the viewer perceive two faces or one face in alternation. This kind of illusion, where the viewer experiences two equally possible interchangeable stable states in perception, is called a bistable illusion. It is impossible to see them both simultaneously. www.mastermathmentor.com

56. The Leaning Tower Illusion The Petronas Towers appear as if the tops of the buildings would touch if they were built any higher. The image outlines converge. But we have repeated the image of the Leaning Tower so the two image outlines are parallel. Our visual system assumes that they must be diverging as they recede from view, and this is what we see. The same illusion works horizontally as well. Again, these picture are the same. Shown to the right are two images of the Leaning Tower of Pisa. Which one leans more? It turns out that these are the exact same pictures. www.mastermathmentor.com

57. The Ambiguous Cylinder Illusion Shown to the right are images of cylinders and the image when seen through a mirror. The rounded cylinders have a mirror image of square-shaped cylinders and vice versa. How can this be? This illusion was created by Kokichi Sugihara in 2016. What is this shape? A trapezoid or a square seen in perspective? By using an object’s shape to counteract perspective, we can encode a different shape in the same object. The secret of the illusion is that the shapes are neither circles nor squares but something in between (called squircles). It can be nudged to look like one or the other depending on the angle it is viewed. To create the illusion, lighting, shadows, and the focal length of the camera’s lens must be taken into account. www.mastermathmentor.com

58. Color Assimilation Illusion You can see a colored background grid and 3 disks, covered by parts of the background grid. The question is: Which color do the disks have? The 3 disks are all light yellow. Change the side of the covering grid does not change the illusion. This phenomenon is aptly known as “assimilation”, since the disk colors become similar to the mixture of the grid lines covering it. www.mastermathmentor.com

Sources 52. Dress - https://www.sciencealert.com/10-viral-optical-illusions-broke-the-internet-cognition-perception 53. Strawberry - https://www.sciencealert.com/10-viral-optical-illusions-broke-the-internet-cognition-perception 54. Curvature Blindness - https://www.sciencealert.com/10-viral-optical-illusions-broke-the-internet-cognition-perception 55. Venetian Mask - http://illusionoftheyear.com/2011/05/mask-of-love/ 56. Leaning Tower - https://www.sciencealert.com/10-viral-optical-illusions-broke-the-internet-cognition-perception 57. Ambiguous Cylinder - https://www.sciencealert.com/10-viral-optical-illusions-broke-the-internet-cognition-perception 58. Color Assimilation – https://michaelbach.de/ot/col-assim/index.html www.mastermathmentor.com