Retro-Technics • author: a3310i • last modified: 2021.12.19 •

A military pilot, once examined by psychologists, recounted such an adventure: "The night was extremely dark. My co-pilot was sitting at the controls. I instructed him to guide the plane over the airfield and to land. He began his descent from an altitude of 4,500 feet. I expected him to level the machine at 1000 feet. He did not do so and continued his descent. It was only my intervention that saved the situation. It turned out that the co-pilot had misread the altimeter. Such an incident seems trivial. The thing is, it was not the first time I had witnessed it. Many pilots have lost their lives because they misread the altimeter readings while descending in the dark night."

There are many similar examples. The problem of adapting mechanisms to man occurred with particular vehemence only during the last world war. It was then that specialists - psychologists and physiologists - were asked for help. Intensive research work began to answer the questions of the constructors. It was recognised that common sense, intuition, timing and even the best of intentions are not enough to solve problems related to the adaptation of various devices and mechanisms to their user. They are not enough, first of all, because technological creations have reached a very high degree of complexity. Moreover, the role of man at work has changed. From the former "physical force", lifting weights, manoeuvring heavy hammers, etc., man is becoming a dispatcher, who supervises the work of the machines. As a result, the human energy function recedes into the background, while the control function comes to the fore. This creates a new type of burden: instead of physical burdens, there are more burdens of a psychological nature. This is why the psychological problems associated with work, and in particular with production work, are gaining in importance.

How do labour psychologists see specific courses of action in adapting machines to humans? This can be well represented by a simple diagram. Such a diagram contains three essential functions: information reception, decision and execution. The first function - in the course of work some signals are constantly received. These signals are divided into different types. A natural signal is one that arises as a direct result of the work - for example when working on a lathe it is a loss of material. Artificial signals are additional stimuli such as signal lights, buzzers, bells or notices.

Depending on how the signal is perceived, you have to decide on a specific action. This is the second function in the diagram. When it comes to relatively simple, routinised work, such as working on a production line, the decision seems relatively easy to make. In jobs that are performed under fluctuating conditions, the decision may be more difficult. An example of this would be driving a car in constantly and rapidly changing traffic on a street. The quality of decisions in the course of work, their accuracy depends on many circumstances, but above all on the quality of information that is needed to make a decision. The more complete the information, the better the decision. The final stage is the execution of the decision, usually some movement such as pressing the pedal, turning the steering wheel, changing the settings on the control board, or hitting with a hammer.

[001] Saab Nightpanel. This feature switches off unneccesary lights and indicators. It increases concentration on the road. When particular parameter is in warning mode, its indicator will be switched on.

What does it mean to facilitate the reception of information? First of all, it consists in shaping all devices in such a way as to enable a human being to receive information in the fastest, easiest and error-free manner. Research indicates that human visual perception is guided by specific regularities. If the task is to read an instrument that has one pointer and a scale, it is not a matter of indifference what shape the scale will have and how it will be placed. Tests have been carried out in which a very short time of 0.12 seconds was given to read the correct value. In one of the research works it turned out that the most errors were read from a scale placed vertically. Slightly better was a horizontal scale, and the best was a window scale. With this type of scale, in the window there is only the part where the pointer is located.

[002] Percentage of bad readings depending on the type of analogue scales. Noticeably the best solution is the window scale.

The second fundamental problem, which has its psychological aspects, is the design of all executive devices, control devices, by means of which we influence the operation of mechanisms. For example, the direction of movement of a rotary control device should be in the direction of movement of the controlled device. In addition, some general directions of movement of switches, levers and rockers have been found in research. The movement of the switch to the right is perceived by people as switching on, opening, while the movement to the left is perceived as switching off, closing. The forward movement of the lever is associated with acceleration, turning on, increasing. Backward movement is associated with slowing down, switching off, decreasing. Also important are issues such as resistance of the lever, ergonomics of the handle or steering wheel, clear arrangement of controls. All these aspects contribute to making the right decisions quickly. In order to harmonise the work of man and machine even better, each of the points raised should be analysed and studied in detail. This is the only way to contribute to increasing the psychological comfort of work and eliminating human errors.

[003] The controls on the bridge of a modern ship.