“Normal” Disabilities

The brain shapes our inner reality, and in my previous post I discussed the way neurological damage can distort our reality-sense. I offer other examples in Your Living Mind. But those of us who are “normal” also experience the world in ways that are irrational. Scientists are discovering more and more ways in which normal humans suffer from perceptual disabilities. Perception does not just duplicate the outside world, as if we were photocopy machines.

One example of a normal disability is inattentional blindness. It may seem as if we would surely be aware of anything we’re looking at directly. But if people are paying attention to one thing they may not see something else, even if they are gazing straight at it. In one study subjects were asked to stare at a fixed point, but they had to report whenever an X appeared a few inches away from the point they were gazing at. So they were looking at one point but staying alert for randomly appearing Xs nearby. Partway through this task, without warning, some letter or shape would appear at the fixation point, right where they were looking. Many did not see what unexpectedly appeared, even though they were looking right at it!

Interestingly, some kinds of items were usually noticed. “The two most reliable of this small group of attention-capturing stimuli are one’s own name and the iconic representation of a happy face” (Arien Mack, “Is the Visual World a Grand Illusion? A Response,” Journal of Consciousness Studies, May/June, 2002, p. 108). But if even one vowel in the name is incorrect, we are unlikely to detect it, “suggesting that it is the meaning of the stimulus that captures attention and not some lower-level stimulus attribute” (p. 109). After information about what we are staring at travels up the optic nerve into our brains, cerebral sentries note the significance of this perceptual data, and decide whether to let it become conscious.

Here’s a frightening example of inattentional blindness. Pilots in training use a simulator to practice flying while they’re safely on the ground, watching a screen that duplicates what they would see out the windshield of an aircraft. At one point NASA was testing a display that projects navigational information onto the windshield, as if the information were floating out in front of the airplane. Sometimes pilots were “using a display, commenting on how nice it was, while landing their aircraft right on top of another aircraft taxiing onto their runway in plain view” (Daniel Levin, “Change Blindness Blindness As Visual Metacognition,” Journal of Consciousness Studies, May/June, 2002, p. 127). Their attention was on the new display, so they overlooked a huge moving obstacle right in front of them!

Roger Christan Schriner

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Change the Brain, Change “Reality”

The brain creates our core sense of reality, and we can learn a lot about that by noticing what happens when it is damaged by aging, accident, or illness. For example, sometimes an injury or a stroke alters neural structures that help constitute our experience of reality, including concepts of front and back, left and right, clockwise and counterclockwise. Then it’s as if one of the stage sets for our personal Truman Show has suddenly collapsed. (See “Your own little Truman Show,” December 8, 2014.)

In rare cases after a stroke, a patient’s visual experiences become a mirror image of normal experiences. As a result, books can be read only if they’re held up to a mirror. Such individuals write the mirror image of their signature and want to drive on the left-hand side of the road! That’s a fairly basic reality shift.

Or consider hemineglect, in which people ignore half of their world as if it isn’t there (usually the left half). When asked to copy a drawing of a flower they only draw the right side. They still realize that every object has two sides, but the brain modules which structure their experience of the world in terms of left and right have been damaged.

Neurologist Oliver Sacks tells of a stroke patient who would only eat the right half of a plateful of food. She could, of course, have turned the plate around after eating half of her meal. Then the neglected left half would have become the effortlessly-noticed right half. But since it was so hard to focus on “leftness,” she would physically move, turning around in a circle to the right. Looking at the plate again she would see the remaining food – or at least the right side of what was “left” over. She would do this several times, consuming one half after another until only crumbs remained.

This patient was highly intelligent and could even joke about the conceptual predicament of hemineglect. “It may look funny, but under the circumstances what else can I do?” When she tries to rotate the plate rather than rotating herself, “it is oddly difficult, it does not come naturally, whereas whizzing round in her chair does, because her looking, her attention, her spontaneous movements and impulses, are all now exclusively and instinctively to the right.” “‘It’s absurd,’ she says. ‘I feel like Zeno’s arrows – I never get there’” (The Man Who Mistook His Wife for a Hat, pp. 77-78).

In mentioning Zeno, she was referring to a Greek philosopher who asked how an arrow could ever arrive at its target. After all, before the arrow lands it has to go halfway, before going halfway it has to go 1/4 the distance, before that 1/8, and so on ad infinitum. Thus the stroke patient consumed half of her food, 1/4 more, and so on. So even though she knew she was succumbing to an illusion, her compelling inner sense of the way things are overwhelmed her intellectual insight.

So when the brain changes, reality changes – or seems to.

Roger Christan Schriner