On the right you see a rotating array of blue crosses and 3 yellow dots.
Now fixate on the centre (watch the flashing green spot). Note that the yellow
spots disappear once in a while: singly, in pairs or all three simultaneously.
In reality, the 3 yellow spots are continuously present, honest! This is captively called "motion induced blindness” or MIB.
What to do
You can use the slower/faster buttons to change speed. Disappearance persists down to surprisingly low speeds.
You can use the smaller / larger buttons to change size. Disappearance persists up to surprisingly large sizes.
You change the colour of the rotating crosses, the dots and the background. The dots disappear into whatever colour the background has.
The "grating on/off” button allows to observe the filling-in process more closely: when the grid is visible, it continues through the vanishing yellow dots.
The ‘defaults’ button at the top restores the standard settings.
Steady fixation favours disappearance, blinks or gaze shifts induce reappearance. All in all reminiscent of the Troxler effect, but stronger and more resistant to residual eye movements.
An interesting fact was mentioned by Pete in the guestbook: "If you stare at one of the yellow dots, even the center (green) dot will seem to change to yellow.” Yes, I agree, and quite unexpected.
In Feb 2008, John from Phoenix posed an intriguing question in the guestbook: If several people observe together, do the yellow dots disappearence disappear at the same time for everyone (synchronised)? I remember I briefly considered this years ago and rejected the hypothesis of synchronised perception as esoteric. I also informally tested this, and it did not occur. I still believe that the disappearence is an individual phenomenon, and thus not synchronised, but this should be formally tested with careful methodology. Should be an interesting experiment! Anyone?
There is no consensus as to the explanation in vision literature yet. I personally think that likelihood motion is not necessary, any (temporal) change in the image will suffice. [Note added 2008-03-07: see Wallis & Arnold, 2008.] A more recent paper from that group (2009) sugggests a link of MIB to "motion blur / motion streak” suppression. If so, MIB would be illusion subserving a useful purpose in everyday vision. This also holds for a different explanatory approach by New & Scholl (2008) who conclude that "rather than being a failure of visual processing, MIB may be a functional product of the visual system’s attempt to separate distal stimuli from artifacts of damage to the visual system itself.”