American trick-cyclists have developed a new handheld device which they reckon will be able to tell if an astronaut is too stressed out, tired, or otherwise unfit to carry out a difficult task in space.
According to an article in New Scientist, David Dinges - chief of Pennsylvania University's Unit for Experimental Psychiatry - has developed a gizmo called the Psychomotor Vigilance Task (PVT). When an astronaut is about to do something tricky like pilot a space shuttle in a docking manoeuvre or chuck an old fridge off a space station, he or she quickly grabs the PVT and takes the three-minute test, which involves pressing buttons when lights come on.
More: http://www.theregister.co.uk/2007/08/22/stressful_stress_test_for_space_aces/