The artist as neuroscientist Artistic licence taps into the simplified physics used by our brain to recognize everyday scenes , says

301 Although we rarely confuse a painting for the scene it presents, we are often taken in by the vividness of the lighting and the three-dimensional layout it captures. This is not surprising for a photorealistic painting, but even very abstract paintings can convey a striking sense of space and light, despite remarkable deviations from realism. The rules of physics that apply in a real scene are optional in a painting; they can be obeyed or ignored at the discretion of the artist to further the painting’s intended effect. Some deviations such as Picasso’s skewed faces or the wildly coloured shadows in the works of Matisse and other Impressionists of the Fauvist school are meant to be noticed as part of the style and message of the painting. There is, however, an ‘alternative physics’ operating in many paintings that few of us ever notice but which is just as improbable. These transgressions of standard physics — impossible shadows, colours, reflections or contours — often pass unnoticed by the viewer and do not interfere with the viewer’s understanding of the scene. This is what makes them discoveries of neuroscience. Because we do not notice them, they reveal that our visual brain uses a simpler, reduced physics to understand the world. Artists use this alternative physics because these particular deviations from true physics do not matter to the viewer: the artist can take shortcuts, presenting cues more economically, and arranging surfaces and lights to suit the message of the piece rather than the requirements of the physical world. In discovering these shortcuts artists act as research neuroscientists, and there is a great deal to be learned from tracking down their discoveries. The goal is not to expose the ‘slip-ups’ of the masters, entertaining as that might be,but to understand the human brain. Art in this sense is a type of found science — science we can do simply by looking. To count as a ‘discovery’ in this art-based neuroscience, deviations from standard physics must be mostly invisible to the human eye in casual viewing. A painting that, despite physical impossibilities in the depiction, gives an unhindered sense of the space and objects within it, says something about our brain. For example,a shadow that looks like a convincing shadow, even though its shape does not match the object that cast it, suggests the physics of light and shadow used by our visual brain is simpler than true physics. This simplified internal physics employed by our visual brain is not used just to appreciate paintings, but to enable our rapid and efficient perception of the real world. Real shadows are subject to an extensive set of constraints, but few of these seem to be checked by our vision; that is why an artist can use an unrealistic representation with such great impact. It is important to note that the simplified rules of physics that interest us (and the artists’ shortcuts that exploit them), are not based on the ever-changing conventions of artistic representation, as they hold for monkeys and infants, both quite immune to the conventions of art. These simplified rules are grounded instead in the physiology of the visual brain.