Philosophers have for centuries debated the nature of “reality”, and whether the world we experience is real, or an illusion. But modern neuroscience teaches us that, in a way, all our perceptions must be considered illusions. By “perceptions” here, I mean, not just our perception of the physical world, but also of the social world. Let’s consider first, how we perceive the physical world.

Consider your eyesight. The image of the world you “see” is an artificially constructed picture whose character and properties are as much a product of your unconscious mental processing as they are

a product of real data. Look at the image to the left. It is the view of a road, as it would appear if recorded by a human retina, with no additional processing. 

Unprocessed, the data collected by your eye yields a rather poor picture. But your unconscious fixes it – and it does so before you are even aware of any perception. In addition it reads flat, two-dimensional data from your retinas and creates the sensation of three dimensions. Our brains do all of this without conscious effort, and we accept the visions concocted by our unconscious minds without question, and without realizing that they are only an interpretation.

That brings up an important theme in neuroscience: a central function of the unconscious is to construct a useful reality, and to fill in the blanks in the face of incomplete information. That applies not just to our perception of the physical world, but also to our social perception.  For example, suppose you meet someone new. You have a quick conversation, and form a picture of that individual’s character. But how much of that do you really know, and how much have you unconsciously filled in, just as you fill in the visual data your eye collects? 

In one telling experiment, scientists investigated how our unconscious uses the sound of a stranger’s voice to help fill in the blanks. The scientists asked a set of volunteers to read scripted answers to political and personal questions, and then created four versions of each answer by electronically raising and lowering the speakers’ pitch, and by quickening or slowing their speech rate. The resulting speech still sounded natural, and its acoustic properties remained within the normal range. 

The scientists then recruited dozens of other volunteers to judge the speech samples. Since the content of the speakers’ answers didn’t vary amongst the different versions, but the vocal qualities of their voice did, differences in the listeners’ assessments would be due to the influence of vocal qualities and not the content of the speech. 

The result: speakers with higher-pitched voices were judged to be less truthful, less emphatic, less potent, and more nervous than speakers with lower pitched voices. Also, slower-talking speakers were judged to be less truthful, less persuasive, and more passive than people who spoke faster. If two speakers utter exactly the same words, but one speaks a little faster and louder and with fewer pauses and greater variation in volume, that speaker will be judged to be more energetic, knowledgeable and intelligent. And if you speak with much modulation in pitch and volume, and a minimum of noticeable pauses, you will increase your credibility and project the impression of intelligence

Just as our brains fill in the details of an image our eyes record only roughly, so too do our brains employ tricks we are unaware of to fill in details about people we don’t know intimately. In filling in the blanks about people, our unconscious mind employs factors such as voice, looks, dress, body language, and even at times wishful thinking, or, sadly, prior beliefs based on ethnic stereotypes. And we normally accept these impressions without realizing the extent to which they are the guesses of our unconscious mind, or what factors our unconscious mind employed to make those guesses. More about this in future blog entries.

Adapted from: Subliminal: how your unconscious mind rules your behavior  Copyright Leonard Mlodinow 2012

About the Author

Leonard Mlodinow

Leonard Mlodinow is the author of Subliminal: How Your Unconscious Mind Rules Your Behavior.

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