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<h1 class="reader-title">Why do the dots disappear?</h1>
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<p>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 <em>three</em> yellow
dots, they remain there as well.</p>
<p>But now concentrate on the <em>central green
dot</em>. 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
<em>doesn’t register their presence</em> from
time to time. Weird, eh?</p>
<p>GIF url:<br>
</p>
<address><a class="moz-txt-link-freetext" href="https://whyevolutionistrue.com/2014/09/02/why-do-the-dots-disappear/anigif_enhanced-16656-1408614979-1/">https://whyevolutionistrue.com/2014/09/02/why-do-the-dots-disappear/anigif_enhanced-16656-1408614979-1/</a><br>
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<blockquote>
<p>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<sup><a
href="http://www.nature.com/news/2001/010614/full/news010614-9.html#B1">1</a></sup>.
[JAC: for some reason the reference isn’t
given.]</p>
<p>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.</p>
<p>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.</p>
<p>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.</p>
</blockquote>
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<p>The researchers suggest this may (and I suggest
that it certainly must) happen in daily life:</p>
<div>
<blockquote>
<p>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.</p>
<p>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.</p>
<p>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<sup><a
href="http://www.nature.com/news/2001/010614/full/news010614-9.html#B2">2</a></sup>.</p>
<p>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.</p>
</blockquote>
<p>My only question is why it takes motion to
generate this illusion. Is that because motion
is associated with visual confusion?</p>
</div>
<p>Source of gif: <a href="http://michaelbach.de/">Professor
Michael Bach</a> at the University of
Freiburg, via reader Grania. Bach has<a
href="http://michaelbach.de/ot/index.html"> a
page with 113 of these damn things</a>!</p>
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