New data brought by the Sleep and Learning Lab at Michigan State University have shown that caffeine doesn't help sleep-deprived people to execute complicated actions. However, something around two cups of coffee may improve drowsy people's ability to keep concentrated on some simple tasks.
To discover this, scientists asked 275 people to do first simple and then more complicated tasks. Participants were randomly split into two groups: the one who slept in their home and the one who spent the night sleep-depriving under supervision in the lab. Then, in the morning, all participants had received 200 milligrams of caffeine before they started to do their tasks. You can find the full study results in the Journal of Experimental Psychology: Learning, Memory, & Cognition where they were recently published.
The study, led by MSU Psychology Associate Professor Kimberly Fenn, showed that between these two groups the sleep-deprived one performed worse, which was expected. However, caffeine clearly helped sleepy people to perform simple tasks, but showed no beneficial effect when it comes to complex tasks - the ones that require a series of steps that must be done in a particular order and without repetition.
"While caffeine can help to stay awake and follow the task, it doesn’t grant protection from all sorts of procedural errors that can lead to medical mistakes and car accidents,” emphasized Fenn.
There is also a recent German study about sleep deprivation and caffeine's influence on cognitive performance. That research proved that a small amount of coffee can reduce negative cognitive repercussions caused by the lack of sleep. At the same time, the study showed that the benefits of coffee are limited and can't replace real sleep.
"Coffee can bring more energy, diminish drowsiness or even raise your mood, but it can't by no means replace a full night of rest in bed," Fenn said. "There is a common delusion that caffeine can help to overcome sleep deprivation effects, but the truth is their ability to do complex tasks will be flawed. And that misconception is one of the main reasons why sleep deprivation is considered so dangerous.