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.

The evolutionary primacy of the brain's fear circuitry makes it more powerful than the brain's reasoning faculties. The amygdala sprouts a profusion of connections to higher brain regions -- neurons that carry one-way traffic from amygdala to neocortex. Few connections run from the cortex to the amygdala, however. That allows the amygdala to override the products of the logical, thoughtful cortex, but not vice versa. So although it is sometimes possible to think yourself out of fear ("I know that dark shape in the alley is just a trash can"), it takes great effort and persistence. Instead, fear tends to overrule reason, as the amygdala hobbles our logic and reasoning circuits. That makes fear "far, far more powerful than reason," says neurobiologist Michael Fanselow of the University of California, Los Angeles. "It evolved as a mechanism to protect us from life-threatening situations, and from an evolutionary standpoint there's nothing more important than that."

I've already written about this sort of thing.