Clinical Associate Professor of Data Science and Psychology Pascal Wallisch tackles Twitter’s most pressing questions about visual illusions for Wired

NYU Center for Data Science
3 min readJan 20, 2023

The visual perception expert explains the science behind blivets, motion-induced blindness, mirages, the viral dress image, and more

Clinical Associate Professor of Data Science and Psychology, Pascal Wallisch

When Clinical Associate Professor of Data Science and Psychology Pascal Wallisch received an email from Wired looking for “tech support experts” he almost didn’t respond as his initial thought was: “aren’t we all?” Soon enough he was answering questions submitted by Twitter users about frustrating and fascinating visual illusions on a recent episode of Wired’s Tech Support video series. By explaining the science behind these puzzling images, he illuminates how and why our minds trick us into seeing things that aren’t there.

“Have you seen the [visual] illusion where you stare at the spiral then look away and things appear to be crawling,” a question by one Twitter user asks to open the episode. While black and white spirals spin across the screen, Pascal describes to viewers, they are experiencing what is known as the “motion after effect” when they look away. When looking at the spiral the neurons in the brain underlying the perception of motion are activated, but after a while, they get tired and will fire at a lower rate when viewers look away producing a false perception of motion.

These popular visual illusions are how psychologists shed light on the difference between what’s out there in the world and how we individually perceive reality. They play with our neural systems, taking advantage of the assumptions made by the brain in visual processing. While optical illusions like mirages are created by light, Pascal clarifies that visual illusions are created by the visual system of the brain. The episode goes on to show just how extensive this processing is by breaking down questions submitted about 3D movies, the Ames room, the Tupac hologram, and blivets which he explains as “impossible objects” like the Penrose stair illusion.

Another type of visual illusion explored in the video has to do with how prior experience factors into perception. For example, another Twitter user wanted to know if there was an explanation for the illusion behind “the dress”: an image of a black and blue dress that went viral in 2015 when some saw it as blue and black while others saw gold and white. In the episode, Pascal discusses his research which has shown morning people with more of a lived experience in environments with natural light perceive the dress as gold while night owls with more of a lived experience with artificial lighting, typically see the dress as blue.

Individual differences in perception is a research topic Pascal is currently exploring at NYU’s Fox Lab where he serves as Principal Investigator. The hub brings together the fields of data science, psychology, and neuroscience to explore questions about personality and cognition. To watch the full Wired video go to Neuroscientist Answers Illusion Questions From Twitter, to read more about the illusions discussed in the video go to Fox Lab’s Tech Support References, and for one last visual illusion check out “Scintillating Starburst” below, introduced by Pascal Wallisch and Michael Karlovich. Viewers will perceive beams of light radiating out from the center of the concentric rings of polygons.

“Scintillating Starburst”, a visual illusion introduced by Pascal Wallisch and Michael Karlovich.

by Meryl Phair



NYU Center for Data Science

Official account of the Center for Data Science at NYU, home of the Undergraduate, Master’s, and Ph.D. programs in Data Science.