An object viewed directly (foveal vision) appears noticeably different from the same object viewed indirectly (peripheral vision). To investigate this aspect of how we see, our illusions accentuate the differences between foveal and peripheral perception. In one of these illusions, the “peripheral escalator,” zebra-like columns swing back and forth across the screen. Viewed foveally, the columns appear to move along a horizontal path; viewed peripherally (focus your gaze several inches above the screen), the columns appear to shift back and forth along a diagonal path. The results illustrate that peripheral vision is not just a blurry version of foveal vision.
Click on the big button to toggle between a blurred version of the display and an unblurred version. When the display is blurred, the motion is dramatic; when the display is not blurred, there is only minimal motion. The effect can also be seen with a defocused lens. Blur eliminates high-spatial frequencies. It does not add information to the image. Why, therefore, does the removal of high-spatial frequencies add motion to the display? The buttons and levers allow control over the many of the parameters in the display.