Optical Illusions

Your eyes can deceive you; don’t trust them — Obi Wan Kenobi in Star Wars: A New Hope

Don’t let your eyes deceive you, quips the well known adage. Although the statement, which instructs us to look beyond outer appearances, is meant to be taken figuratively, it’s literal meaning is, quite surprisingly, of some significance (the sword still overshadows the pen as a weapon, however) provided that “eyes” is replaced by “mind.”

Our first encounters with mind tricks took place either during a magic show or on the big screen, when our immature Star Wars-drunk minds voraciously gobbled up the numerous occasions in which the mysterious robe-wearing Jedi convince white-clad dull-witted goons (armed only with the worst accuracy in the universe far, far away) to do their bidding with a flourish of their hand. Like many elements of sci-fi movies, the Jedi mind trick lost all applicability when used in the modern world, but we still longed for a way to make these senseless fantasies into reality. Of course, these thoughts gradually receded as more important affairs supplanted them. In reality, we don’t need any superhumans from the future to beat our brains into submission.

A synergistic cooperation between our eyes and ears yields an interesting phenomenon known as the McGurk Effect. When researchers played a video of a human repeating “bah,” test subjects identified the sound correctly. However, after playing the same audio in conjunction with a video of the same person repeating “fah” the test subjects reported that the sound was a “fah,” not the “bah.” Neat little trick, right? In certain situations, not so much. In another experiment, subjects watched two people chasing each other. While an actor remarked that “he’s got a boot,” some subjects, perhaps influenced by the tension of the situation, remarked that the actor actually said that “he’s gonna shoot.” Obviously, this misunderstanding might lead to some unintentionally bogus legal cases.

Next, look at this. Stare at the green dot and look nowhere else.

After a few seconds, you may realize that the yellow dots are blinking in and out. Then, imagine that you’re driving in the night, staring at the road as cars pass by in sudden, intense bursts of headlight beams and mechanical rumbling. The road is the green dot and the yellow dots are cars. Sometimes, as we can see, it’s not that the driver is inebriated or sleepy, so don’t blame the driver when he/she says that “it came out of nowhere.” This phenomenon, called motion-induced blindness, is caused by the brain’s filtering of what it perceives to be unnecessary information: because the blue grid is moving and the yellow dots are not, the brain filters out the yellow dots. To prevent this phenomenon from happening, airplane pilots are trained to keep their eyes on the move and desist from staring at anything for more than a few seconds.

Although the visual illusions may seem like trivial playthings we get sidetracked by while scrolling through Facebook, they can have serious real-world repercussions.

–William Cho (’21)

Images: Google Images

Leave a Reply