Perception is a tricky concept, for it always goes hand in hand with our senses, especially our visual senses and when it happens, we usually can not report what’s going on. Perception gives us a vague feeling that something should be like this or like that. For a better understanding, we need to separate sensation and perception.

There is a simple way, however, to distinguish these two processes: When you pick up your phone and are ready to take pictures of something, ask yourself a question—does the camera on your phone know the picture it captures?

This question might sound creepy, bizarre, or even stupid. A lucid person could easily shoot out his answer: of course it doesn’t, it is the man behind the camera knows the picture, or perhaps it does, if a certain recognition system is built in. Well, that’s the point: the eyes are camera-like light receptors, while perception organizes features collected by eyes into a meaningful whole. We do not see things with our bare eyes; we “see” things using our mind’s “eye”—perception.

Evidences that Mind’s “Eye” is Working Well in Everyday Life

Our visual experience, strictly speaking, is a subjective psychological process that accomplished mostly by perception. We don’t need to search academic papers to prove the existence of our mind’s “eye”. Rather, daily life experiences as follows will suffice:

(1)   In spite of being “cheated”, perception strives to integrate the information coursing through your eyes into a meaningful whole all the time. If you google or baidu “illusory contours”, you will “see” the contours that objectively does not exist. (link: https://en.wikipedia.org/wiki/Illusory_contours)

(2) Our eyes are also light receptors and these two crystal balls are anatomically like cameras. The images projected on retina or films are actually 2D. Why we see the world effortlessly in real 3D? It is a mathematically impossible task that transforming a picture from 2D to 3D with a dimension completely unknown. Well, basing on cues, our perception is good at doing such “educated guesses”. 

(3) The very moment we see things, we recognize them and attach meaningful tags to them. We don't see and describe things in a camera-like fashion. In everyday life we say: I see a tree; I see green leaves on the tree; I see flowers around the tree. We don’t see and describe things in terms like light and shades, colours and forms, contours and backgrounds: I see this brownish thick stick and something greenish on the top; I see intense light coming from this direction and its shadow goes to that direction (If you are interested or an expert in photography or art, that’s another story).

Visual Agnosia: When Mind’s “Eye” is “Blind”

In the last section, I am to talk about people who suffer from visual agnosia(a term coined by Sigmund Freud, who then was little-known neurologist). My tutor’s sister is an agnosic girl and I met her several times during my college years.

Visual agnosia is caused by lesions in certain areas of cerebral cortex and it appears in various forms according to the damaged areas. The girl suffers from visual object agnosia: she can normally see, but what courses through her eyes doesn't make any sense. If I was a few steps away from her, she often mistook me for some movie stars or pop singers (a different star at a time, which was quite comforting). However, she was able to know who I am when I was close enough for her to “examine”: she smelled on me, touched my face, and said my name.

Perception does its job in such a perfectly smooth manner that we make sense of what we see without conscious efforts. For a long time, we all have taken what perception does for granted. When perception fails us, the consequences are indeed devastating. There are many mental processes happening outside the realm of consciousness just like perception. I will cover some of them in later writings.