In the study, Dr Eichele and his colleagues asked participants to repeatedly perform a "flanker task" -- an experiment in which individuals must quickly respond to visual clues.

As they did so, brain scans were performed using functional magnetic resonance imaging (fMRI).

They found the participants' mistakes were "foreshadowed" by a particular pattern of brain activity.

"To our surprise, up to 30 seconds before the mistake we could detect a distinct shift in activity," said Dr Stefan Debener, of Southampton University, UK.

"The brain begins to economise, by investing less effort to complete the same task.

"We see a reduction in activity in the prefrontal cortex. At the same time, we see an increase in activity in an area which is more active in states of rest, known as the Default Mode Network (DMN)."

This has security implications whenever you have people watching the same thing over and over again, looking for anomalies: airport screeners looking at X-ray scans, casino dealers looking for cheaters, building guards looking for bad guys. It's hard to do it correctly, because the brain doesn't work that way.