Lack of sleep can put you in harm's way-literally.
We already know how lack of sleep can cause several health consequences, including the increased risk of obesity and metabolic syndromes. But there's one more reason why you should hit the bed early and get the most ideal number of hours: you cannot tell the difference between a good and a bad guy.
People rely on intuition and facial expression to have a general idea about the person and his or her emotions. For example, if we see someone who's grimacing, most probably that person is feeling some physical pain. The same mechanism is also being used when you want to avoid being mugged. Your brain can tell you if a face is threatening, so you'll have ample time to defend or avoid the mugger altogether.
However, the major problem when a person lacks sleep is that the ability to read faces drops significantly. In other words, you cannot properly distinguish good and bad facial expressions.
This is the major finding of a study conducted by UC Berkley PhD student and Stanford University's postdoctoral fellow Andrea Goldstein-Piekarski, as well as UC Berkeley neuroscience and psychology professor Matthew Walker, who also serves as the study's senior lead author.
For the study, they conducted an experiment with almost 20 young adults, all of whom are in healthy condition. They were allowed to sleep for the recommended number of hours as well as to stay awake for 24 hours. In every time period, they viewed 70 images of facial expressions, some of which were menacing. They also used a special kind of MRI scan to monitor brain activity and a hear monitor to capture heart rate.
During their analyses of the results, those who were deprived of sleep didn't register any recognition on threatening faces. There's also no change in the heart rate, which may suggest the participants weren't able to detect the distressing situation.
