Tom Cruise, Keira Knightly, Angelina Jolie: When viewed one at a time on a computer screen, photographs of gorgeous celebrities highlight pleasing features on generally symmetrical faces. But if you look at the same images side-by-side while focusing on a cross between them, something bizarre happens. The faces begin to morph, becoming bulbous and grotesque, especially when one member of a pair has a face that is structured very differently from the other.
The optical illusion, as described in a 2011 research paper and illustrated in a disturbing YouTube video, is just one example of how our senses often distort reality -- a concept illustrated in a recent Dove ad that showed how other people tend to see us as more beautiful than we see ourselves. In the video, an FBI forensic artist drew women as they described their own faces and as others described them.
Through studies of illusions like these, along with research on vision, brain science and memory, researchers are beginning to understand the limits of our ability to interpret the endless reams of input that we absorb all day long. We often see things that aren’t there and don’t see things that are.
And while many details about the relevant brain processes remain mysterious, it seems that our innate tendency to distort reality can be a useful trait.
“One way we think about perception is that it’s an interpretation of the world rather than a veridical representation of the world because it makes us function in the world,” said Kalanit Grill-Spector, a neuroscientist at Stanford University in Palo Alto, Calif. “If you were representing exactly what was hitting your eyes, it might not be optimal for your behavior.”
She offered a red tomato as an example. If you were to use a spectrometer to measure the wavelengths of light that bounce off of a tomato in different environments, the quality of the fruit’s redness would appear to be wildly different when held outside than it would in the produce aisle of the supermarket. To our eyes, however, the same tomato looks equally red in both places, and that kind of color constancy allows our brains to understand that a tomato is a tomato, no matter where it is.
In another famous illusion, an image can appear to be a duck or a rabbit, depending on which part of the picture you focus your eyes on.
“In this situation where an ambiguous stimulus is prone to multiple interpretations, your brain has to resolve it,” Grill-Spector said. “There might be competition in your brain and it might be happening all the time. If you are walking in the fog and it’s not clear what you’re seeing; you have to make an inference.”