In our 21st century world of wanting to do more and more in less time, skilled multi-tasking has become the holy productivity grail. But, the research shows that multi-tasking, the attempt to do two or more tasks at the same time, is really just fast task-switching and the costs are heavy - people make more mistakes or perform their tasks more slowly.
Key Takeaway
Our brains are unable to keep two things in mind at the same time. That means the brain can’t multi-task. When we think we’re multi-tasking, we’re actually switching tasks quickly. When we try to multi-task, the cognitive resources available to both tasks is reduced, resulting in reduced productivity and increased errors. The cost in productivity may be as high as 40%.
The human attentional system has limits for what it can process.
Much of the research on multi-tasking has looked at driving while performing another task, such as texting, eating, or speaking to passengers in the vehicle, or with a friend over a cellphone. This research reveals that the human attentional system has limits for what it can process: driving performance is worse while engaged in other tasks; drivers make more mistakes, brake harder and later; they get into more accidents, veer into other lanes, and are less aware of their surroundings.
In one study that looked at brain activations during distracted driving, the participants drove in a simulator under varying difficulty levels. They also listened to an audio of general knowledge true or false questions (such as a triangle has four sides) and answered the questions by pressing buttons on the steering wheel. So the design of this study was similar to real driving conditions.
The researchers found that as the driving conditions became more difficult - turning left into oncoming traffic - the audio task shifted brain recruitment from the crucial parietal and visual cortices, which are responsible for spatial and visual processing, to the frontal areas, responsible for executive functions including attention, working memory and decision processes. Obviously, this is not a good thing. When we need our parietal and visual cortices the most, turning left into oncoming traffic, the frontal areas hijack some of our crucial spatial and visual brain power to accomplish the audio task.
When we multi-task, the cost in productivity may be as high as 40%.
Although this study looked specifically at multi-tasking while driving, there are many other studies that have looked at multi-tasking in other domains, and the results are similar: They show that when trying to do two tasks at once, the cognitive resources available for both tasks are reduced and performance in both tasks suffers.
The solution seems obvious: If we want to do more in less time, we should really concentrate on one task at a time.