What's happening in our brains when we can't see something that is literally right in front of our eyes?

I keep getting more questions about visual perception that are probably more neuroscience and philosophy oriented than strictly ophthalmic. Here are some of them:

What's happening in our brains when we can't see something that is literally right in front of our eyes?

Why can't I find things that are sitting right in front of me?

Why do we sometimes look for items that are right in front of us?

There are many perceptual, cognitive, and neurological explanations for not seeing things in front of us -and for seeing things that are not really there, such as optical illusions. The reason is that we do not really see what is "out there" but rather we project onto the "out there" what we generally expect to see. In most all situations, we predict what we will experience in the senses, and we use the senses to confirm that we are right. What we attend to is highly influenced by our desires, need for security, past experiences, and cultural conditioning.

So "seeing" is not a passive sensory process. This active projection of our brains onto the world runs counter to what we think is going on. But it explains the answer to the above questions: If something we are looking for is not in the expected position, or is upside-down, or has been moved even a short distance away from where you remember it, IT MAY AS WELL NOT BE THERE. As my mother would say "If it were a snake it would have bitten you!"

_Written by J. Trevor Woodhams, M.D. - Chief of Surgery, Woodhams Eye Clinic