110 Are the Androids Dreaming Yet? . Lire eS a fs : = A Toes Nw [eases eter rete. r ih “~, © : aN ‘2 rhe \ &. | SR ws ~ yy a, Oe. ._ = Piso Mi “ | yw ' i Frogs Eyes are Very Sensitive The processing power of the eye is staggering. The human retina has about 120 million rods and 7 million cones, giving it an average resolution of 10,000 by 10,000 pixels. Each rod is sensitive to individual photons but we register light consciously only if we see around 5-7 photons. It is thought frogs can react to single photons because of the chemistry of their eyes and the fact they are cold-blooded, but this is not proven. Some animals, including some frogs and my cat, have a tapetum lucidum. This is a reflective backing to the eye that allows each photon two chances to react with a rod, once on the way in and, if that fails, once on the way out. This is why you can see the eyes of some animals if you shine a light into the forest on a dark night. Cones are less sensitive than rods but give us color perception. In the human eye, there are three types of cone: a red, a green and a blue, giving us trichromatic vision. We see colors because light stimulates more than one types of cell and we infer the color in between. A fourth type of cone is present in some species such as birds, reptiles, and fish. This gives them tetra-chromic vision, allowing them to see into the ultraviolet range. It is speculated some humans might have this ability but so far none has come forward. Some animals lack the ability to see certain colors. Most dogs can't see red. This gives cats a big advantage! Many people wonder if we all see the same color as each other. Is your red the same as mine? ‘The brain’s perception of color is complex. Although the color red is absolute and can be detected by a calibrated sensor, our perception of color is relative. We perceive them in the context HOUSE_OVERSIGHT_015800