Optical illusions are always fascinating. They trick our brain to perceive things differently than they actually are. Optical illusions are indeed a reminder that things that we see are not always as they seem.
A recent video on Instagram published by physicsfun brings another excellent example of optical illusion designed by Sugihara, a mathematics professor, and an award-winning illusion artist.
The video shows a tiny arrow made up of plastic pointing in the right direction. When this arrow is rotated 180-degrees to point it towards left, you’ll notice that it is still pointing in the same direction.
While this may seem like a magic trick, the always-right arrow is actually tricking your brain to perceive it that way. This brain-bender was first proposed by Sugihara in a 2016 paper published in the Journal of Symmetry.
He described it as an “anomalous mirror symmetry” that is generated by an optical illusion. These types of objects do not obey the rules of typical mirror symmetry.
That is, in reality, the object points in one direction, but in the opposite direction in reflection. This impossible symmetry cannot exist physically but can be perceived by human vision systems because of an optical illusion.
However, Sugihara showed that anomalous mirror symmetry can be generated by designing ambiguous cylinders, which are neither perfectly circular nor perfectly angular.
"When we see the object and its mirror image, however, what we perceive does not necessarily obey this physical law, because what we perceive is the result of image processing in our brains," Sugihara mentioned in the paper. "Hence optical illusion arises."
If you look closely, the arrow isn’t actually an arrow. In reality, it is an oval shaped object made up of different curved surfaces. The edges of each surface meet at the center.
Viewing this object at a certain angle and with suitable lighting conditions creates an optical illusion that tricks your brain to consider these curves as angles. This is essentially due to our brain’s preference towards interpreting retinal images as 3D objects in right angles.
In his paper, Sugihara has demonstrated in detail the use of such nature of our brains using different geometrical shapes that appear different in the original posture and in the mirror image.
The always-right arrow isn’t the only optical illusion example. The video below demonstrates another mind-bending illusion through the use of ambiguous cylinders.
A set of plastic squares appears to circles in the mirror and simultaneously turns into squares when rotated.
The professor has won twice in the Neural Correlate Society’s Best Illusion of the Year Contest. With his novel idea, he believes that the visual effects created with such unordinary change of the appearance of the object might be used for new artistic presentation.