An optical illusion is more appropriately known as a visual illusion. It involves visual
deception. The arrangement of images, effect of colors, impact of light source and any other
variables cause you to see a wide range of misleading visual effects. Have you ever
struggled to see the hidden image in a single-image stereogram? If you have, then you
might have discovered that not everyone experiences visual illusions in the same way. As a
matter of fact, some people are simply not able to see the effect of some illusions.
Optical illusions are so much fun and interesting but more than that, they reveal a great
deal about the working of the brain. The most famous optical illusion is the Hermann Grid
The Hermann grid illusion
The Hermann grid was discovered by psychologist Ludimar Hermann in 1870. Looking at
the grid, a viewer sees white dots and at the center of each corridor, the white and gray
dots seem to be shifting. While focusing attention on a specific dot, a viewer can tell that is
obviously white but as soon as their attention drifts, the dot shifts to a gray color.
So how does the optical illusion work?
How come a person sees gray where there should be white? The bigger question is why you
see something so different from that which is in reality? Traditionally, the explanation is
given by what is known as lateral inhibition. Lateral inhibition is a phenomenon which
demonstrates a very important principle of perception. The perception is that we do not
always see what is really there. Your perceptions depend on how your visual stimuli
system responds to environmental stimuli and how your brain then interprets this
However, this theory may be inaccurate is some way. The illusion is not dependent upon
size, can be seen with contrast reversal and can be negated by slightly distorting the lines.
These are the reasons cited for the inaccuracy of the theory.
The other possible explanation is the S1 simple-cell theory.
Don’t you find it fascinating that your eyes can trick you into seeing something that is not
really there? Generally, optical illusions work because your brain needs a little rest.
Therefore, it has devised a few shortcuts along the way like colors, shadows and
perspectives which help it understand what it is seeing. Your brain then starts to form an
opinion based on these clues.
The clues can be optical illusions designed to induce things like:
● Lateral inhibition as in the Hermann grid illusion
● Pareidolia where you see faces in inanimate objects
● Troxler’s effect where things in peripheral vision to fade
Optical illusions fool or get your brain confused.
Optical illusions and neuroscience are tightly interwoven because optical illusions are used
to study the human brain especially how it interprets the information our eyes send to it.
Your eyes take an enormous amount of information in a very short time e.g. an image. The
brain will continue to process subconsciously after seeing the image creating a situation
where your eyes are constantly trying to figure out what they are seeing and your brain
constantly telling them what to look at next. This sounds very exhausting even for the