OPTICAL DELUSION

The picture of the world we
“see” is artificial. Our brains
don’t produce an image the
way a video camera works.
Instead, the brain constructs a
model of the world from the
information provided by
modules that measure light and
shade, edges, curvature and so
on. This makes it simple for the
brain to paint out the blind
spot, the area of your retina
where the optic nerve joins,
which has no sensors. It also
compensates for the rapid jerky
movements of our eyes called
saccades, giving a false picture
of steady vision.
But the downside of this
process is that it makes our
eyes easy to fool. TV, films and
optical illusions work by
misleading the brain about
what the eye is seeing. This is
also why the moon appears
much larger than it is and
seems to vary in size: the true
optical size of the moon is
similar to a hole created by a
hole punch held at arm’s length.