[D66] Optical Illusions: Why do the dots disappear?

[René Oudeweg]

whyevolutionistrue.com 
<https://whyevolutionistrue.com/2014/09/02/why-do-the-dots-disappear/>


  Why do the dots disappear?

3–4 minutes
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This is one of the most baffling illusions I’ve ever seen. Take a look 
at the gif below.  First, look at any yellow dot as the figure moves. 
The yellow dot remains present and stationary. If you concentrate on all 
/three/ yellow dots, they remain there as well.

But now concentrate on the /central green dot/. You will see one or more 
of the yellow dots disappearing and then reappearing sporadically. They 
are not—this is an optical illusion. The dots remain and your brain 
simply /doesn’t register their presence/ from time to time. Weird, eh?

GIF url:

https://whyevolutionistrue.com/2014/09/02/why-do-the-dots-disappear/anigif_enhanced-16656-1408614979-1/

anigif_enhanced-16656-1408614979-1 
<http://whyevolutionistrue.com/2014/09/02/why-do-the-dots-disappear/anigif_enhanced-16656-1408614979-1/>

    Yoram Bonneh, of the Smith-Kettlewell Eye Research Institute in San
    Francisco, and colleagues have been showing people a swirling
    pattern of blue dots superimposed on some stationary yellow dots^1
    <http://www.nature.com/news/2001/010614/full/news010614-9.html#B1> .
    [JAC: for some reason the reference isn’t given.]

    The yellow dots seem to wink in and out. But the erasing happens in
    the mind, not the computer. Nearly everyone tested saw the effect.

    The brain seems to have internal theories about what the world is
    like. It then uses sensory input – which tends to be patchy and
    disorganized – to choose between these. In some sensory situations,
    different theories come into conflict, sending our perceptions awry.

    The illusion, which Bonneh’s team calls motion-induced blindness,
    catches the brain ignoring or discarding information. This may be
    one of the brain’s useful tricks, a deficiency – or perhaps both,
    says Bonneh.

The researchers suggest this may (and I suggest that it certainly must) 
happen in daily life:

    The researchers speculate that this phenomenon could happen in
    everyday life without us noticing it. A highway at night, with
    drivers staring dully at a mass of moving lights, might recreate the
    kind of conditions used in the experiments, says Bonneh, causing
    objects – the tail lamp of the car in the next lane, for example –
    to temporarily vanish.

    Jack Pettigrew, a neuroscientist at the University of Queensland in
    Brisbane, believes that the illusion results from a tussle for
    supremacy between the left and right halves of the brain.

    He has found that applying a pulse of magnetism to the brain to
    temporarily disrupt its function affects the occurrence of
    motion-induced blindness. When the pulse is applied to the right
    hemisphere (leaving the left dominant) the dots disappear; zapping
    the left brings them back^2
    <http://www.nature.com/news/2001/010614/full/news010614-9.html#B2> .

    The left hemisphere seems to suppress sensory information that
    conflicts with its idea of what the world should be like; the right
    sees the world how it really is. Some people with paralysis caused
    by injuries to their right hemisphere will deny that they are disabled.

My only question is why it takes motion to generate this illusion. Is 
that because motion is associated with visual confusion?

Source of gif: Professor Michael Bach <http://michaelbach.de/> at the 
University of Freiburg, via reader Grania. Bach hasa page with 113 of 
these damn things <http://michaelbach.de/ot/index.html>!


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