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Ever realised you have driven yourself home but haven’t really been paying attention? Brain scans have revealed that when your mind wanders, it switches into “autopilot” mode, enabling you to carry on doing tasks quickly, accurately and without conscious thought.

Our autopilot mode seems to be run by a set of brain structures called the default mode network (DMN). It was discovered in the 1990s, when researchers noticed that people lying in brain scanners show patterns of brain activity even when they aren’t really doing anything. This research provided the first evidence that our brains are active even when we aren’t consciously putting our minds to work.

But what does the DMN do? Several studies have found that it seems to be involved in assessing past events and planning for the future. Others suggest the network is involved in self-awareness – although this has been called into question by findings that rats and newborns appear to have a version of the DMN too.

It is unlikely that rats are conscious of themselves in the same way that humans are, says at the University of York, UK. Instead, the DMN must have a more basic function, common to all animals. Vatansever and his colleagues at the University of Cambridge wondered if the network might help us do things without paying much attention, such as tying our shoelaces, or driving along a familiar road.

To investigate, the researchers asked 28 volunteers to learn a card game while lying in an fMRI brain scanner. In the game, each person was presented with four cards. They were then given a fifth, and asked to match it to one of the four.

But participants were not told the rules – they didn’t know whether to match the cards by colour or shape, for example. Through trial and error, each person figured it out after a few rounds.

While this happened, their brain activity resembled patterns that are typical of learning minds. But as the game continued, and the participants knew how to match the cards without much thinking, their brain activity resembled those of using the DMN – and their responses became faster and more accurate.

This suggests that when we “switch off”, our brains go into an autopilot mode that allows us to perform tasks reasonably without thinking much about them.

This might also help explain why some tasks – such as playing a well-known tune on a musical instrument – suddenly seem much more difficult when you go from doing them absent-mindedly to consciously thinking about them.

Boost your autopilot

In the experiment, people whose DMN structures are more strongly connected also performed better in the card game. In these people, the various regions fired together more consistently, showing more coordinated activity. This suggests that the more strongly a person’s DMN is linked up, the more effective their autopilot mode, says Vatansever.

It may be possible to train yourself to have a better autopilot mode. In other studies, people have been able to control their brain activity when shown real-time scans of their brains. Similar “neurofeedback” training may enable people to boost their brain’s autopilot mode, allowing them to perform better on tasks without directly focusing on them, says at Ohio State University.