My research paper is about the anatomy of an optical illusion. Optical Illusions are relevant to aviation in that the main guidance system of most aircraft on most flights is the pilot’s eyes. Everyone, including pilots, is susceptible to an optical illusion. The hazards of optical illusions are many considering that at any time during the flight they can cause a healthy and experienced pilot to become confused, delusional and generally disoriented with obvious possible consequences. This is why we must study and be aware of optical illusions so that we may be better prepared should we encounter one at a critical time.
To better illustrate the origins of optical illusions I will review some parts of the brain and their functions. The brain has seven main parts, they are: the thalamus, the hypothalamus, the cerebellum, the brain stem, the corpus callosum, the two hemispheres, and the largest part of the brain, the cerebrum.
The thalamus is located just above the brain stem. It acts like a switchboard, deciding what to do with the messages that come to the brain. If you were reacting to a situation like flying in a dogfight, and radio chatter was coming through your headphones, your thalamus would ignore the radio chatter.
The hypothalamus controls our emotions such as happiness and sadness. It also controls our sense of temperature and our feeling of hunger. It is located directly in front of the thalamus. It is also one of the organs that is fully developed when you are born.
The cerebellum is the part of the brain that controls our muscles. When we are born, our cerebellums aren’t fully developed. That’s why we didn’t do things in a coordinated manner with our limbs. We moved shakily with our bodies because messages from another part of our brain called the cerebrum weren’t organized by the cerebellum.
The brain stem is located at the back of the brain, right below the thalamus. It has the responsibility of taking care of involuntary movements such as breathing, blinking, and making our heart beat.
The cerebrum is the largest part of our brain. It takes care of our motor skills such as speaking, walking, and writing. These skills are operated in the outside layer of the brain, called the cortex. It is the last part of the brain to develop and is unique only in humans. The cerebrum is divided into two halves, or hemispheres. Our major learning senses are located within the two hemispheres.
The corpus callosum is the connector for the two hemispheres of the brain and sends messages between the hemispheres. Your corpus callosum is able to send about twenty messages per second and routes them to various nerve cells called neurons. The brain receives messages through these neurons. Scientists believe that for every ten billion cells in the body, one billion of them are neurons.
Can you see a square?
Scientists at the Massachusetts Institute of Technology discovered that an area of the brain previously thought to process only simple visual information also tackles complex images such as optical illusions. Research, conducted with animals, provided evidence that both the simple and more complex areas of the brain are involved in different aspects of vision and work cooperatively, rather than in a rigid hierarchy, as scientists previously believed.
The Scientists compare vision to an orchestra, where clusters of cells in different parts of the brain cooperate to process different components of visual information such as vertical or horizontal orientation, color, size, shape, movement, and distinctions between overlapping objects.
The MIT research focused on an area of the cerebral cortex, the outer layer of gray matter that envelops the entire brain called the primary visual cortex, also known as V1 and Area 17 of the brain. In humans that area is about five centimeters in diameter, about the size of four postage stamps and a couple millimeters deep on both sides of the rear of the head, just below the crown.
The V1 area is the first point of entry in the brain’s cortex of visual information from the eye’s retina. Earlier the V1 was thought to be involved only in processing very simple spatial orientations, such as whether an object is placed vertically or horizontally, but not whether that object is a pencil or a finger.
Using optical imaging techniques to record visual responses in cats, the researchers found that V1 can also process optical illusions and other complex images. The researchers said the same is likely to be true in the V1 area of the human brain.
For example, if a person takes a sheet of notebook paper with horizontal lines and places an identical sheet as close as possible to the right of it and slightly lower, the lines on both pages won’t connect in a continuous straight line. Yet the brain’s visual processing system will try to fill the space between the two sets of real lines by creating an optical illusion known as a subjective contour (see next picture). Subjective contours are higher-level visual functions that involve the brain’s understanding the context and relationship of the images, not just the static placement of one set of lines next to another. Another example is a telephone: a handset may obscure part of the phone base under it, but the brain’s visual processes will see both the handset and the entire phone base as two distinct objects that belong together.
It is also believed that V1 could also be the site of filling-in, another function traditionally thought to be high-level. Filling-in is when the brain compensates for a lack of information in one area of the visual field by making an educated guess from information elsewhere in the visual field. It explains why patients with small lesions don’t see black spots, and why you are not aware of your blind spot.
An example of Subjective Contour
As for practical applications, our brain and eye are most effective when dealing with the contrasts of objects and movement. This is one of the distinguishing abilities that the sight of mammal predators (such as ourselves) possess. A factor in this ability is the placement of our eyes. When we look at something, each eye focuses on the object and the convergence angle of the two eyes is what we use to judge distance. Our ancestors used this ability to see the range and motion contrast of potential prey. The modern importance of 3D vision can be demonstrated in this simple experiment. Give a friend a tennis ball and have them stand ten to fifteen feet away from you. With both of your eyes open, have your friend toss you the ball. Now catch it with one hand. Easy right? Now try covering one eye with one hand and catching the ball again. Not so easy this time! This is a demonstration of how the eyes work together to give us depth perception. This relates to flying when the pilot’s eyes try to judge the distance and direction of an aircraft far off on the horizon. The aircraft is so far away that our eyes can’t converge on the image and both eyes make almost parallel lines of sight. The aircraft’s true direction cannot be determined at this distance either, even if the aircraft or speck for that matter, is moving to the left or right, the true direction (i.e. coming or going) cannot be determined either. A hazard of this situation is when the aircraft seen on the horizon is dismissed as being too far away to be a factor, but happens to be a directly approaching F-16 flown by an infallible air force pilot!
Along with its vulnerability to illusions, our brain loves to take short cuts. It wants to file everything as simply and quickly as it can. This is one reason that illusions work on us. While otherwise occupied, the brain usually takes in information at face value and works from there. Here is a written example: A father and his son are driving to a baseball game when their car stalls on the train tracks. The train that was coming hits the car, kills the father and injures the son. The son is immediately rushed to the hospital. The boy is on the operating table when the doctor walks in and, upon seeing the boy mutters, ?I can’t operate on this boy, he’s my son.? How can this be? The answer to this riddle lies in a prejudice our brain forms. It says that doctors are men and nurses are women. If this riddle worked on you, your brain took the shortcut of filing the doctor as a man. Average pilots are creatures of habit, following checklists, performing uniform walkaround preflights and flying to familiar airports generally the same way each time. What may manifest from these habitual tasks is complacency. Take for example a pilot who flies a routine VFR night flight to and from the same airports. During the routine cruise leg on a particularly cold and clear night, the pilot leans forward to take a moment to admire the bright stars all around her (Oh, it’s a woman-pilot! There you go again!). After settling back down in the seat, she resets the nose for the horizon and continues her flight. Several minutes go by and she realizes that she is suddenly 1500 feet below her desired altitude. How could this be? When our pilot sat back down she reset the nose for what she thought was the horizon. However she actually set the nose for city lights below/closer than several distant white streetlights that she mistook for stars. The routine of leveling off and continuing the cruise is done so often that we sometimes become complacent and make assumptions.
In conclusion, if we are better prepared and more alert we are less likely to be deceived by optical illusions. Through communication, improved planning and a pilot/co-pilot configuration (two sets of eyes), illusions can be averted and made logic of, and can also provide valuable lessons and experience instead of harsh consequences.
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