What Gets into Our Minds? Perception.
Look steadily at the drawing in Figure 3.
This picture of a Necker cube is made up entirely of black lines in two-dimensional space, but what you perceive is a three-dimensional cube. Looking for some time at this cube produces an apparent reversal, so that the face that was in front becomes the back face of a cube facing the other way.
These representations alternate even if you try not to let them do so. What you are seeing is the brain at work as it attempts to make sense of an ambiguous drawing, unable to settle for one interpretation or the other.
It seems that perception is not just a matter of passively picking up information from the senses, but the product of an active construction process that involves combining input from sensory signals with other information.
We generally assume that the world is as we see it and that others see it the same way—that our senses reflect an objective and shared reality.
Of course if our senses did not provide us with generally accurate information we could not rely on them as we do, but nevertheless psychologists have found that these assumptions about perception are misleading.
Picking up information about our worlds is not a passive, reflective process, but a complex, active one in which the senses and the brain work together, helping us to construct a perception (or illusion) of reality.
Perceiving the Real World
The first stage of perception involves detecting the signal that something is out there. The human eye can detect only a minute fraction, less than 1 per cent, of all electromagnetic energy—the visible spectrum. So what we know about reality is limited by the capabilities of our sense organs.
All senses respond better to changes in the environment than to a steady state, and receptors stop responding altogether, or habituate, when nothing changes, so you notice the noise of the fridge when it switches on but not later.
The Process of Perception
One of the most basic perceptual processes is distinguishing objects from their surroundings. Look at the Rubin’s vase (Figure 5). You will see either a vase or two silhouettes, but not both at once. Seeing the vase makes the silhouettes disappear, but seeing the silhouettes turns the vase into background.
Psychologists hypothesize that there are several crucial steps in this process. Input from the senses (sensation) is fed into the brain which then uses knowledge it already has to construct a model of what is perceived.
Paying Attention: Making Use of A Limited Capacity System
Our brains are limited capacity systems, and to make the best use of them it helps to direct our attention appropriately.
If you audio-record a noisy party you would most likely hear something resembling a confused babble. But if you start talking—or paying attention—to someone at the party, your conversation will stand out against the background noise and you may not even know whether the person behind you was talking in French or English.
Yet if someone mentions your name, without even raising their voice, you will be highly likely to notice it. Normally, we focus as we wish by filtering out what does not matter to us at the time, on the basis of low level information, such as the voice of the speaker or direction from which the voice comes.
What we actually perceive, in combining perception and attention, is thus influenced by internal factors such as emotions and bodily states as well as by external factors.
People who fear social rejection more readily notice signs of unfriendliness than of friendliness, such as negative facial expressions, and hungry people judge pictures of food as more brightly coloured than pictures of other things.
These findings confirm that so much of perception goes on outside awareness that we cannot be sure that there is a good match between what we perceive and reality, or between what we perceive and what others perceive.
This introduction to the field of perception only starts to answer questions about what gets into the mind. The subject covers many more fascinating topics ranging from ideas about perceptual development to debates about the degree to which the processes involved in perception are automatic or can be intentionally controlled.
The aim has been to illustrate the point that reality as we know it is partly an individual, human construction. Each of us makes it up as we go along, and psychologists help us to understand many of the conditions which determine how we do this.
If we know something about what gets into the mind, we can go on to ask how much of it stays there, becoming the basis for what we learn and remember.
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