How do we see things upright if the image formed on the retina in our eye is an inverted one?
Asked by: Shweta Kala
It is true that the images formed on your retina are upside-down. It is also true
that most people have two eyes, and therefore two retinas. Why, then, don't you
see two distinct images? For the same reason that you don't see everything
upside-down. One of our most remarkable tools - the brain - is hard at work for us
at this task.
Processing visual information is a complex task - it takes up a relatively large
portion of the brain compared to other senses. This is because your brain performs
several tasks to make images 'easier' to see. One, of course, is combining the two
images, which is helped by the corpus callosum, the tiny part of your brain which
joins the two big hemispheres. The other part is handled in the optic part of your
brain itself, and part of its job is to make images right-side-up. It does this
because your brain is so USED to seeing things upside-down that it eventually
adjusts to it. After all, it's a lot easier to flip the image over than it is to
try and coordinate your hands and legs with an upside-down world! As a result,
though, it is believed that for the first few days, babies see everything
upside-down. This is because they have not become used to vision.
Your brain CAN be retrained though. In one psychological study, participants were
asked to wear inverting lenses - lenses that invert the image BEFORE they get to
your eye, so that when your eye inverts it, it's right-side-up. At first,
everything appeared upside-down to the participants. But, after a few days, people
began to report that everything appeared right-side-up! As a second part of the
study, the people were asked to take the glasses off. Because they were now used
to the lenses, their NORMAL vision appeared upside-down!! Within a day, though,
their vision returned to normal. The reason you don't see everything upside-down,
then, is simply because it's easier to think about right-side-up!
Answered by: Michael Brady, Computer Engineering Undergrad., NCSU, Raleigh