Scientists don't know what causes it, but besides a genetic predisposition, they are now focusing on environmental exposure, or a combination of the two.

VOA: standard.2010.08.09

Besides the actual performance, they look at how long it takes the soldiers to complete their tasks, since time can make the difference between survival or death for those who are lucky enough to be alive after the nuclear blast.

VOA: standard.2010.07.21