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28 January 2012 | NewScientist | 17 Computer is blind to its own actions Quantum jiggles measured in an ordinary object NOT all brightly coloured animals are trying to draw attention to themselves. Golden moles are blind and spend their lives in darkness but sport beautiful iridescent coats, thanks to hair that may be designed for repelling water rather than attracting a mate. Matthew Shawkey of the University of Akron in Ohio took samples from four golden mole species, all with blue or green iridescence. Electron microscopes revealed that the hairs were flattened into paddle shapes, giving a greater surface area to reflect light. Unusually, the scales on each hair contained alternating light and dark layers. Each layer bent the rays of light just like oil on water (Biology Letters, DOI: 10.1098/ rsbl.2011.1168). Shawkey says this is the first example of a multilayer reflector in hair. The iridescence is an evolutionary accident, he believes. The hairs’ structure may make them more sturdy, repel water, or streamline the moles so they can move quickly through dirt and sand. “Penguin feathers are flattened like this,” he points out. I’m pretty and I don’t know it MICHAEL & PATRICIA FOGDEN/MINDEN PICTURES/FLPA Pupils constrict at thought of light IT IS the light we think we see that counts. Optical illusions designed to seem brighter than they are make your pupils constrict a little more. This suggests that we have evolved systems for anticipating dazzling light to protect our eyes. Our pupils’ fast response to light appears to occur even without input from the brain. For example, it is seen in people with damage to the visual cortex. Appearances can be deceptive, though. Bruno Laeng of the University of Oslo in Norway measured tiny changes in pupil size as volunteers viewed various illusions that were all identical in brightness, though did not look so. If light levels alone dictated pupil size, they would have reacted identically whichever image a person viewed. Instead, people’s pupils constricted more when they viewed the illusions designed to appear brightest (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1118298109). “What’s surprising is that even something as simple as how bright we think our environment is will be affected by our expectations,” says Stuart Peirson of the University of Oxford, who was not involved in the study. Previous studies show that the brain controls pupil size in other situations: our pupils dilate when we make decisions, for instance. PLAINPICTURE/LUBITZ + DORNER For new stories every day, visit newscientist.com/news
