Visual Perception and Who We Are


In The Mind is Flat, Nick Chater uses our flawed intuitions about how we see to question the veracity of the intuition that we have a cognitive subconscious. My review will focus on what Mr. Chater calls “the grand illusion”; our belief that we see much more than we do. Our thoughts and actions are dependent on our perceptions. What we have perceived in the past influences our present perceptions as our current perceptions continue to create who we are and how we will perceive in the future. Illusions can cause us to believe that we are seeing what we know cannot be true. I cannot express this better than the author’s words.
Perceiving is a type of thinking. Indeed, it is perhaps the most important type; and all other types of thought are really just extensions of perception (though powerful extensions). We see far, far less that we think we do. Indeed, we see the world one snippet at a time; and we can tie snippets together, just as we can link together successive sentences in a story.

The following reference to “impossible objects” relates to drawings such as those by M. C. Escher which look real when you look at the whole scene, but you realize are impossible as you study the detail. The phenomenon of ‘impossible objects’ may seem to be no more than a momentarily entrancing party trick, but it provides deep insights into the nature of perception, and is a powerful metaphor for the nature of thought.


The limited visual ‘window’ depends, to some extent at least, on where we are looking. Yet we typically have only the vaguest sense of which part of an image or scene we are looking at directly – we have the impression that the entire visual scene is simultaneously ‘grasped’ in pretty much complete detail. These illusions enable you to experience this. The feeling created is that the picture is changing, not that we are moving our eyes.


How many black dots can you see?
It turns out that, as with so many convincing tricks, the grand illusion depends on misdirection. We point our fovea (we only see clearly within a 5-degree diameter of where our eyes are aimed) and concentrate our attention, on one aspect of the visual world, and notice scarcely anything of what is happening in all the rest. If we are suspicious, even for a moment, that our perceptual representations are rather vague and monochrome in the periphery of our vision, we swivel our eyes across to check, and, sure enough, all is detailed and colourful…. It is as if the visual system has a single metaphorical ‘hand’ that can reach out, select and manipulate just one pattern at any moment.
The grand illusion tricks us into believing that our focus of attention is far wider than it actually is…. We have little or no access to information that is not attended to…. If you don’t pay attention to a word, you just don’t read it. Indeed, from the brain’s point of view, it isn’t there.
Perception, then, is a process of incredibly rich and subtle inference – the brain is carefully piecing together the best story it can about how the world might be, to explain the agitations of its sense organs…. Perception is not merely inference – it is, of course, unconscious inference…. Consider, when deep in a novel, how our flow of the experience is taken over by the story – while we have no awareness at all of the mysterious process by which the brain transforms sequences of printed letters into images and emotions.
Scanning a perceptual scene or reading a text, our eyes jump, on average three to four times a second. During a typical eye movement, the eye will be in motion for between about 20 to 200 milliseconds, depending on the angle through which the eyes ‘jump’. During this period, we are in effect almost completely blind…. It is rather astonishing that we are, from the point of view of conscious experience, entirely oblivious to the highly discontinuous process by which our eyes gather information. (Also consider that we blink many times a second but do not perceive any interruption in our vision. This is also known as Saccadic Suppression.)
The brain’s goal is to inform us about the world around us, not about the workings of our own mechanisms…. This is not surprising: we can’t introspect how our lungs or stomachs work – why should it be any different from the brain?


Perception works by relating, often in the most flexible and creative fashion, our sensory input with our memory of past experience…. Perception and memory are therefore intricately entwined. Recognizing a friend, a word or a tune requires not merely linking together different aspects of the perceptual input, but connecting these fragments to stored memories of faces, words and melodies…. Today’s memories are yesterday’s perceptual interpretations…. As today’s thought or action is tomorrow’s precedent, we are, quite literally, reshaping and reinventing ourselves thought by thought.
We are programmed to develop from what we see and how we see. This is dependent on nature and nurture as are all areas of development. Undeveloped vision is not ready. Its development can be guided. Faulty perceptions lead to faulty thinking. Faulty development is more challenging but can also be improved. Enhancing our vision to enhance our potential is often overlooked.

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