Why don't we always see what's in front of our eyes?

You are walking down the street looking in front of you and suddenly, someone says hi to you. You turn your head and see your friend. How did that happen? Why didn't you see him when you were walking before he caught your attention? These things happen to people, because we are hardwired to ignore most of the things around us. 😮

Just take a look at this video, for example.

How our brains trick us

When we walk around in the world, we think we see everything that is in our visual field. This is because our brains create a cohesive illusion of the world around us to our conscious mind. This is needed because the amount of information coming from the eyes in massive. Imagine a computer trying to process two sources of live images and do object recognition in real time. It's just not possible, not even for the brain. 🤖

All the data, the rays of light projected to your eyes' retinas, gets transferred to the brain. This is what is called sensation. But the brain cannot process all this data, so it picks out the pieces we will consciously see. What our conscious mind sees is called perception. The difference is that what is perceived, has gone through a filter: the brain picking up the most relevant pieces of information we need. For instance, we don't need to see every single leaf of a tree, it's quite enough that we see that there are some leaves in a tree. What we will see is filtered by attention. We only perceive what we pay attention to.

More information is added than what we actually see

Perception is not just about picking up the relevant pieces of information we will actually see. Simple everyday things such as colors are created by the brain. Of course, eyes have cone cells that will tell the brain "the color" of the light they receive, but this is not quite enough. The actual color we will see, is decided by the brain depending on the overall context. We don't usually see the color of our clothes changing when we go indoors from outside, even though the light the sun emits is quite different to the whole range of different kinds of lamps we use in buildings. As a result, the sensation changes because the light changes, but the perception remains the same. 👁️

To illustrate this, take a look at the example video below. You will see a black and white castle in colors. 😲


That was all for this time. If you are interested in how eyes or other senses work, there's a book called, Sensation & Perception, which has very good examples of different phenomena related to how our senses function. 😄