Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
The Secret Life of the Brain
History of the Brain 3-D Brain Anatomy Mind Illusions Scanning the Brain The Episodes:

Mind Illusions can you believe your eyes?

Spiral
Do we know what the world looks like?

The eye is made up of some of the most amazing tissue in the body. The lens, for example, is perfectly clear, perfectly curved and is capable of focusing on an incredible amount of data. But vision has only partly to do with the retina, lens, and cornea. Understanding what we see mostly happens in the brain, which is why a person with perfect vision is still susceptible to optical illusions. Do we know what the world looks like? We know approximately what it looks like, which is enough to get by, but our perception of the world is not without a certain amount of 'misreading.' Our visual nervous system approximates color, shape, and dimension.
photo of an eye A person with perfect vision is still suspectible to optical illusions.

The process of seeing begins with the presence of light, an image being formed on the retina, and an impulse transmitted to the brain, but there are many other factors that play a part in how we perceive visually. Our perceptions are influenced by our past experiences, imagination, and associations.
Movement
Movement
Why does it feel like this spiral is sucking you in?

see for yourself
Color
Color
Can you tell the difference between these two colors, or is that a trick question?

see for yourself
Angles
Angles
Parallel lines may seem harmless but it's all about the angles.

see for yourself
Form
Form
How could you forget this face?

see for yourself



about the series outreach make a pledge feedback sitemap shop