“See? Humans actually can multitask.”

I’ve had that message sent to me several times over the past month, usually by people who know I occasionally challenge the multitasking myth. The reason was a new study published in the Journal of Cognitive Neuroscience. The researchers trained participants more than 30,000 times to categorise novel, artificially morphed cars. After this intensive training, participants became better at combining that task with a second one, while the researchers also observed clear changes in the underlying brain networks. Interesting, but…

The study does not actually show that humans can multitask. In fact, it argues almost the opposite. It starts from an idea that has been central to cognitive psychology for decades: the prefrontal cortex acts as a kind of bottleneck. Processing two attention-demanding decisions simultaneously is inherently limited. That is why we make so many mistakes when we try to perform two complex tasks simultaneously.

What the researchers demonstrate is much more subtle than evidence for multitasking. After an extraordinary amount of practice, the categorisation task appears to rely less on the prefrontal cortex. Activity shifts partly towards visual areas, connections with motor regions become stronger, and connectivity with the prefrontal cortex decreases. At the same time, participants become better at performing the categorisation task while carrying out a second task.

That may sound like multitasking, but it is really a textbook example of automaticity. When you first learn to drive, changing gears requires your full attention. After years of experience, it happens almost without conscious thought. That does not mean experienced drivers have suddenly become capable of performing two demanding cognitive tasks at once. It means that one of those tasks no longer requires much central attention.

That is exactly what this study appears to show. Not that the bottleneck has disappeared, but that a highly practised task no longer needs to pass through it to the same extent. As a result, more capacity is available for a second task. After all, we have always done several things at once. We breathe, walk, and tap away on our phones simultaneously. The catch is that, while doing so, we often notice remarkably little about what is happening around us.

To be clear, none of this makes the study any less interesting. Quite the opposite. It provides a compelling neural explanation for something cognitive psychology has described for decades: extensive practice changes not only how quickly we perform a task, but also how the brain organises it. That is a fascinating finding. It is simply not the same as concluding that humans are actually good at multitasking.