Christina Draganich and Kristi Erdal's study, which appeared in the Journal of Experimental Psychology, evaluated 50 students. The participants rated how well they had slept the previous night on a scale of one to 10. After splitting into two random groups, they received a short lesson on the benefits of sleep (generate neurons, make rational decisions, up your immune system). The researchers told them that people who get less than 20% of their sleep time in REM perform worse in cognitive tests, as opposed to those who spend 25% in REM. Then, Draganich and Erdal hooked up the students to a device that measured their REM sleep from the previous night by assessing heart rate, pulse, and brainwave activity — except they completely made up the part about the machine, as that technology doesn't exist.
Afterward, the first group was told they had 16.2% REM, and the other group 28.7% — both fake results. The students took a PASAT test, which involved adding numbers and was intend to "assess auditory attention and speed of processing." The 28.7% crowd met the normal performance standard, but the 16.2% group scored below average. The researchers then wondered if having a doctor tell a person they got enough sleep could trick their brain into thinking it was true.
Draganich and Erdal decided to take things one step further: Could this same method improve cognitive ability? In a second experiment, they added more controls and expanded their pool to 114 participants using three different tests. They saw similar results to the first experiment. The group who believed they had more sleep tested better than their snoozy counterparts, but not on all three tests.
So, what does it mean? The research duo believe that it's "possible to provide cognitive enhancement from verbal instruction on sleep quality.” They added that “by understanding that one’s mindset nonconsciously contributes to the existence of physiological and cognitive limits, an individual may then be able to consciously extend those limits, experiencing improved cognitive functioning, perhaps without even actually altering sleep patterns.” Of course, if you know you're lying to your brain, it will not have the same effect. But, this study does illuminate a different side to the placebo effect. (Motherboard)