There are thousands of optical illusions, and this is a variation on what is known as the Adelson Illusion. The illusion demonstrates how we can be fooled into thinking that what looks like white is actually black and that the frame or context plays a huge role in the way things look to us.
The dot in the boxes above has the same gray scale value in every box. The changing gray scale value of the enclosing boxes is what produces the apparent change of shade in the dot. In other words, you can’t trust everything you think you’re seeing, and you need to guard against allowing the changing context to fool you into thinking there has also been a change in content.
For example, the setting of a church or other place of worship is likely to exert contextual power over anything going on inside because the associations we have with religion influence how we think. We probably aren’t thinking the same way in a church as we are in a car dealership, or a pool hall, or a hospital emergency room, or WalMart–with each place lending the power of its context to what we are thinking and how we are reacting.
Noticing this illusion for the first time can be unsettling. No matter how hard we try, it is just about impossible to believe that the dots at either end of the bar above are the same shade of gray! Implications? Understanding that we can be fooled by optical illusions should raise some questions for us about trusting sensory experience in general. Do we need to always view sensory data with suspicion? Granted, the illusions, of course, are contrived and designed to pinpoint the problems in the hard-wiring of our optical system, but are there any positive qualities revealed by these illusions? How would very young children react? What about someone who comes from a pre-technology (stone tools) culture? In other words, is everyone experiencing the same effect? Why?
Try to be mindful of the powerful influence that context has on your experiences and try to regard your sensory apparatus with a little skepticism. We don’t need much help fooling ourselves; we seem to be pretty good at it already.