This information can come handy in building a device that warns us when we're drifting off.
In the study, Tom Eichele of the University of Bergen in Norway, Stefan Debener of the Institute of Hearing Research in Southampton, England, and several colleagues used functional magnetic resonance imaging (fMRI) to monitor the brains of thirteen subjects as they undertook the "flanker task."
In that classic psychological test, subjects select one of two buttons depending on the direction of arrows displayed on a screen.
Analyzing the brain's blood-flow patterns, the team found that a subject tended to blunder after the brain simultaneously activated a set of regions associated with rest, and reduced activity in a different area associated with staying on task.
The change began up to half a minute before an error occurred, and the brain seemed to refocus after the subject caught the mistake.
This research challenges a long-standing theory that the brain flubs simple tasks because of fleeting, random errors in neuron firing.
The study has been published in the Proceedings of the National Academy of Sciences.