快猫短视频

Why don鈥檛 we notice impossible lighting and unlikely reflections in realistic-looking paintings? The answer is all about speed

IT IS a joyous occasion 鈥� the newborn Virgin Mary gets her first bath, surrounded by attentive nursemaids. Her mother, exhausted from the birth, reclines on a golden dais in an alcove. All are bathed in beautiful light that floods in from all directions. But hang on a second. Where is all this light coming from, when there is only one arched opening and a small window to illuminate the alcove in the plaza? And why do the people in the foreground cast deeper shadows than those further back?

Although nothing seems amiss at first glance, the more you look at this painting by Fra Carnevale, the more incongruities you find. 鈥淵ou couldn鈥檛 recreate the Carnevale scene with all the spotlights in Hollywood,鈥� says , a neuroscientist at Paris Descartes University in France and at the Vision Science Laboratory of Harvard University.

Yet we rarely notice these discrepancies because the brain鈥檚 intuitive understanding of light and reflection is so poor. Indeed, Cavanagh鈥檚 studies have found that when the brain analyses a shadow, it doesn鈥檛 notice discrepancies in the direction of light, the shape of the object or the distance between an object and its shadow (). Artists like Carnevale cashed in on this trait to create atmospheric scenes that couldn鈥檛 possibly exist.

Reflections in mirrors are equally challenging to the brain. When at the University of Liverpool, UK, asked people to look at Diego Vel谩zquez鈥檚 , in which a cherub holds up a mirror to Venus as the goddess lies with her back to us, the majority assumed Venus was admiring herself. Yet viewers can see Venus鈥檚 face reflected in their direction, making it physically impossible that she is admiring herself (Perception, vol 32, p 593).

This inability to gauge mirror images, so exploited by artists, is reflected in real life, too: Bertamini has shown that despite having mirrors all around us, we are appalling at predicting what should be visible in them (Cognition, vol 98, p 85). This inability was particularly troubling for one Francisco Scaramanga, James Bond鈥檚 arch enemy in The Man with the Golden Gun, whose confusion in a hall of mirrors cost him his life.

So what are the benefits of a brain that works to a different set of rules from the world we live in? According to Cavanagh, it鈥檚 all about speed. You couldn鈥檛 do a proper analysis of all the laws of physics in the tenth of a second it takes your visual system to form an image, he says, so we evolved a small set of rules that can be computed rapidly without requiring a large proportion of our brain.

Read more: Six ways that artists hack your brain