![]() Let us examine these phenomena more closely. The letters are too perceptually complex and fine-grained to be aided by the vestibular correction, even though the overall orientation of the page is corrected to look upright. The page continues to be difficult to read, even though vestibular information is clearly signaling to you that the page and corresponding text are still upright in the world compared with your head's orientation. Now, holding the magazine right side up again, try bending down and looking at it through your legs-so your head is upside down. Just turn this magazine upside down to find out. Upside-down print, for instance, is extremely hard to read. There are clear limits to vestibular correction. There is no image in the brain to “rotate”-and even if there were, who would be the little person in the brain looking at the rotated image? In the rest of the essay, we will use “reinterpret” or “correct” instead of “rotate.” These terms are not entirely accurate, but they will serve as shorthand. The phrase “takes into account” is much more accurate than saying that your brain “rotates” the tilted image of the table. Instead your brain figures out which way is up by relying on feedback signals sent from the vestibular system in your ear (which signals the degree of head rotation) to visual areas in other words, the brain takes into account head rotation when it interprets the table's orientation. The surrounding context is not the answer either: if a luminous table were placed in a completely dark room and you rotated your head while looking at it, the table would still appear upright. We know that correct perception of the upright table is not because of some “memory” of the habitual upright position of things such as a table the effect works equally well for abstract sculptures in an art gallery. You will see that it does indeed look rotated, as it should. Now imagine tipping over a table by 90 degrees, so that it lies on its side. Obviously, the objects (tables, chairs, people) continue to look upright-they do not suddenly appear to be at an angle. ![]() First, tilt your head 90 degrees while looking at the objects cluttering the room you are in now. Let us probe those complexities with a few simple experiments. No such rotation occurs, because there is no replica of the retinal image in the brain-only a pattern of firing of nerve impulses that encodes the image in such a way that it is perceived correctly the brain does not rotate the nerve impulses.Įven leaving aside this common pitfall, the matter of seeing things upright is vastly more complex than you might imagine, a fact that was first pointed out clearly in the 1970s by perception researcher Irvin Rock, then at Rutgers University. Although people often believe that an upside-down image in the eyeball gets rotated somewhere in the brain to make it look right side up, that idea is a fallacy. THE LENS IN YOUR EYE casts an upside-down image on your retina, but you see the world upright.
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