Luminance levels of four disks modulate in time. The top two disks become white when the bottom two disks become black, and viceversa. When placed against a split background, the disks group together along the diagonals. This grouping pattern follows the contrasts of the disks relative to their backgrounds.
The binding problem is a fundamental issue in neuroscience. The term refers to the fact that the brain processes color, motion, and other visual features separately and in parallel, yet our perception is of a unified world, populated by coherent objects. Here we investigate the binding problem with illusions that show—rather dramatically—that features can bind and rebind to moving objects. We show that this effect depends on the color of the background and on whether observers view the illusions centrally or peripherally.
In baseball, a curveball creates a physical effect and a perceptual puzzle. The physical effect (the curve) arises because the ball’s rotation leads to a deflection in the ball’s path. The perceptual puzzle arises because the deflection is actually gradual but is often perceived as an abrupt change in direction (the break). Our illusions suggest that the perceived “break” may be caused by the transition from the central visual system to the peripheral visual system. Like a curveball, the spinning disks in the illusions appear to abruptly change direction when an observer switches from foveal to peripheral viewing.
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.
In the perpetual collisions illusion, the pink and the yellow columns seem always to be headed towards (or away from) each other, but they never meet (and they never grow further apart). Actually, the colored fields are completely stationary; an appearance of motion is generated by the spinning black and white diamonds located alongside the columns. Click on the button to add diagonal bars and remove the edges from opposing diamonds. Notice that the information at the edges makes the colored fields move diagonally, yet when the bars are not there and all the edges are visible, the fields move horizontally.
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.
The red button adds/removes half of the background grating. The swimmers bob up and down when they are in front of the grating but not when they are in front of a uniform background
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