 The Brain / Museum / Illusions / Interpretive / Rotating Head |
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The display is a mask of Albert Einstein that rotates on an axis. The mask rotates in one direction only, but we get the impression that Einstein's head is moving back and forth to the left and right. This illusion illustrates the dominant effect of past experience. We're so used to seeing faces projecting outward that we ignore any clues telling us a face may be hollow. The mask actually rotates in a complete circle continuously and smoothly. However, when the hollow side faces us, we actually perceive it as protruding outward and turning in the "wrong" direction, which makes Einstein's head appear to be moving alternately left and right. When we see the hollow side of the mask, we're getting clues - such as the position of shadows - that it is concave (sinking inward) rather than convex (projecting outward). Nevertheless, when faced with the two options, concave or convex, the brain chooses the wrong one because our life experience carries a lot more weight than the clues about the actual situation. What creates the illusion of rotation in the opposite direction? The brain uses an important clue for identifying the rotation direction: movement parallax. When the brain assumes the mask is convex, the parallax effect is reversed and the brain misinterprets the direction of the movement. On The Dragon's Gaze page, you'll find a demonstration that explains illusions based on movement parallax. There's only a slight difference between the Dragon's Gaze and this one: Here, Einstein's face rotates while we stand in one place, and in the other the dragon remains stationary and we are the ones who move. In relative terms, the effect is the same: the rotation of Einstein mask's to our right is exactly the same as our rotation to the mask's left. Related exhibit: Links:
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Rotating Head
