Motion Induced Blindness

Motion Induced Blindness (MIB) is not likely a term you’re familiar with but it is something you’ve experienced, whether you realize it or not. It’s also known as Troxler’s Fading discovered in 1804. It’s the affect whereby objects that are stationary, in relation to your eyes, simply vanish from your peripheral sight when near things that are moving, again in relation to your eyes. In the first example (click here to open the image) you see a grid of blue crosses that are spinning, three stationary yellow dots and a flashing green dot in the centre which is also stationary. Focus your attention on the flashing dot in the middle and you will soon become aware that the yellow dots start vanishing. Sometimes just one vanishes, or in pairs, or all three will vanish from your sight, but they also randomly re-appear without any rhyme or reason. The reality is though…they never actually vanish. They just look like they do.

Some experiments suggest that motion-induced blindness is linked to a visual mechanism that allows us to experience the world in sharp detail. Our visual system has a time lag, and acts somewhat like a camera with a slow shutter speed. This means we should perceive “motion streaks” behind moving objects. While this can be apparent when we watch the movement of sparklers at night, we are not usually aware of motion streaks because there is a mechanism that prevents them from reaching awareness. Motion-induced blindness appears to be linked to that mechanism.



Focus on the yellow cross (click on the image if there’s no movement)

Research data demonstrates that targets located towards the trailing edges of motion undergo greater MIB than targets at the leading edges of motion.

In the images above, stare at the central crosses and be aware of the yellow dots to either side. They should seem to intermittently disappear. Observers signaled that the dots disappeared more when the moving dots drifted away from, rather than toward, the static yellow dots.

Click on the image if nothing is moving.

In this example, the lilac spots in the lilac chaser fade away after about 20 seconds, leaving a grey background and black cross. Some viewers may notice that the moving space has faded into a moving blue-green spot, possibly with a short trail following it. Furthermore, moving one’s eyes away from the image after a period of time may result in a brief, strong afterimage of a circle of green spots.

Sources
Bonneh, Cooperman & Sagi (2001)
Motion-induced blindness in normal observers. Nature 411:798–801
Wallis TSA & Arnold DH (2008)
Motion-induced blindness is not tuned to retinal speed. JOV 8:11, 1–7
Wallis TSA & Arnold DH (2009)
Motion-induced blindness and motion streak suppression. Current Biology 19:325–329 [website]
New JJ, Scholl BJ (2008)
“Perceptual Scotomas” A functional account of motion-induced blindness. Psychological Science 19(7):653–659

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