If we have slept badly, this is usually noticeable throughout the day. Many people try to compensate for their tiredness with coffee or cola. Most of them feel less productive than after a good night's sleep.
Freely invented measurement method
Psychologists from Colorado College in the USA have discovered that the mere conviction of having slept well has a major effect on the ability to concentrate. The researchers explained to 164 students who took part in their experiment how important restful sleep and, in particular, the REM phases are for mental performance. REM stands for Rapid Eye Movement. These rapid eye movements are typical of the sleep phase. We have the most intense dreams during the REM phase, which is why it is also known as the dream phase.
The researchers claimed to have a machine that measures brain waves and can determine the quality of sleep. The students were connected to the machine overnight. In reality, the measurement method was fictitious; the psychologists had already determined by chance which students supposedly had a good night's sleep and which did not.
Only six participants doubted the study
The next day, the psychologists told one group of students that their REM sleep the night before had been above average. In contrast, they told the students in the second group that their sleep quality had not been good. Both groups then had to solve tasks in which they had to absorb and process new knowledge. In fact, the students with the "good" sleep performed significantly better.
Only six test subjects had expressed doubts about the researchers' statements. Some of the students even believed so strongly in the influence of sleep on performance that they wanted to learn more about their sleep behavior, even though they had been informed about the deception.
More confidence in your own abilities
A study carried out at Witten/Herdecke University also shows the power of lies in connection with mental performance. 40 people were invited to take part in a general knowledge test. One group went into the test unprepared. However, half of the participants took part in preparation. The scientists allegedly showed them the solution words for the test on a screen. The words were first displayed slowly on the screen, then faster and faster until they were no longer legible. The psychologists explained that the test subjects had nevertheless absorbed the solution words and now only had to listen to their intuition during the test. The words that flickered across the screen were actually just randomly selected words that had nothing to do with the solutions.
Here too, the test subjects who thought they knew the solutions subconsciously showed much better results than the other group. The head of the study, Prof. Ulrich Weger, explains: "The feeling of support and confidence in their own abilities were strengthened. We suspect that the people made more effort, were better able to overcome their own fears and thought more systematically. "They were simply better able to access the knowledge they had and this actually improved their performance."
Measurable physical changes
The term placebo comes from Latin and means "I will please". The placebo effect is primarily known for the effect of placebo drugs. It is not based on pure imagination, but triggers measurable physical changes, such as in brain activity or hormone balance. Healers already knew about and used the phenomenon in ancient times.
English 
German