In an unfamiliar environment, a perfectly healthy person sometimes experiences tactile illusions, loses orientation in space. This applies to those who operate in extreme conditions: pilots, astronauts, athletes. The habit of trusting the senses can be disastrous in some situations.
Loss of orientation
According to the US Federal Aviation Administration, five to ten percent of in-flight accidents are caused by pilots falling into sensory illusions. More than 90 percent of these cases end in the complete destruction of the plane and the death of people.
According to research by Chinese scientists, 91 percent of pilots experience deceit to some extent, primarily fighter pilots. Almost always, we are talking about a loss of orientation in space, when during rectilinear acceleration there is a feeling that the car is taking off, and a sharp drop in speed is perceived as a loss of altitude.
It is possible that a violation of the spatial orientation (situational awareness) of the aircraft commander caused the Tu-154B-2 to crash while departing from Sochi airport on December 25, 2016. This is the conclusion reached by the Defense Ministry commission.
Deception of the senses in space
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The main reason for such false sensations (they are also called somatogravitational illusions) is a malfunction of the vestibular apparatus, the part of the inner ear that is responsible for balance and correct spatial orientation. This organ in the form of an accumulation of cells and calcareous formations perceives changes in the position of the head and body in space and the direction of movement.
Sensitive hair cells of the vestibular apparatus are immersed in a gelatinous otolithic membrane, where there are also ear stones (otoliths), the pressure of which on different parts of the membrane depends on the position of the body in space. When climbing to altitude, the pressure of these stones changes, but in zero gravity it does not exist at all, so cosmonauts, like pilots, often become victims of false sensations.
Diagram of the structure of the otolith membrane / Illustration by RIA Novosti. A. Polyanin.
According to the data of last year's experiment by scientists from the Institute of Biomedical Problems of the Russian Academy of Sciences, most often in near-earth orbit people are faced with orientation deception. The crew members of the International Space Station, who had studied their surroundings in advance, felt completely disoriented with the lights off and did not understand in which direction and how long they had to move to reach their goal.
Another type of cosmic illusion is kinetic, when it seems to a person that he, in fact, being at rest, rotates around some axis. Such false sensations often led to the so-called coordinate illusions: the astronaut believed that he was leaning to the left or right, backward or forward, or even upside down.
The brain will fix
However, after three days in orbit, most of the expedition members no longer suffered from false sensations, since the brain was adapting to weightlessness. The experiment with the glasses that flip the image took about the same time.
The fact is that the human eye focuses the image on the retina in an inverted form, but the brain compensates for this, and we see the world as it should. American psychologist George Stratton, who first decided to wear glasses with inverting lenses, determined that the brain needs no more than a week to adapt. By the way, after Stratton took off his glasses, the world appeared before him upside down, but after a few days of forced inconvenience, everything fell into place.
Cafe wall illusion. The gray lines between the black and white squares appear to be at an angle. In fact, they are absolutely even.
The brain still cannot cope with some non-standard pictures - we are talking about visual illusions. They arise either due to malfunctions of the retina and parts of the brain (a classic example is the illusion of a cafe wall), or due to the fact that the actual impact does not correspond to our ideas about the world. For example, having seen a concave mask depicting a human face, observers consider it convex, because previous experience suggests that there are no concave faces.
Visual perception can play a trick on biathletes. As Russian researchers have found out, the shooting accuracy of athletes depends, among other things, on the appearance of the target. If the targets for shooting are modeled after the Mueller-Lyer illusion (the segments of the same length appear different due to the framing of the arrows), athletes are not able to accurately estimate the size of the target, and as a result, the accuracy of shooting is reduced.
Müller-Lyer illusion. Depending on the type of tips located on the sides of the segments, they appear shorter or longer. In fact, all the line segments are the same length.
Captured by tactile sensations
But even basic sensations, which, it would seem, can be completely trusted - tactile, often deceive us. For example, the distance between equidistant points on the skin feels different depending on where they are located, and stroking the tip of the nose with two crossed fingers gives the person the impression that they have two noses.
According to scientists from King's College London, such tactile illusions arise from the structure of the skin. The surface of the human body is divided into so-called receptive fields - areas of the skin dotted with receptors from one nerve cell and stretched along the limbs. In more sensitive areas (for example, at the fingertips) these fields are many and small in size, in less sensitive areas the fields are larger, but they are smaller. The distance between two points is estimated by the brain by the number of these receptive fields lying on the line connecting them. This point of view was confirmed by an experiment in which volunteers perceived the lengths of the segments marked on different parts of the forehead as different, although in fact they were the same.
People with a breakdown in the SCN9A gene, which encodes a protein that forms sodium channels in cell membranes, becomes hostages of tactile illusions. Through them, pain is transmitted to the brain. If the channel is not working properly, no signal is generated and the brain has nothing to process. People in this case do not feel pain at all and do not notice even a very serious injury. According to the testimony of a professor at the University of Cambridge, Jeffrey Woods, one of the carriers of this rare mutation in Pakistan jumped from the roof of a house, deciding that he was invulnerable. Of course, a 14-year-old teenager crashed to death, but his numerous relatives with the same genetic abnormalities later helped researchers understand the mechanisms of pain.
Alfiya Enikeeva