Emergency medical technicians often have to figure out if a patient is really unconscious, or if they're faking it. One of the techniques they use to do this is the "hand drop" test. Steve Whitehead of theemtspot.com describes it:
Without warning, we gently pick up the patients hand and hold it above their face. Without delay, we drop it. If the patient were truely unconsious, the hand would fall and strike them in the face. Most likely on the mouth or chin. We’re not going to let that happen, but the patient doesn’t know that.
Steve notes that the test is remarkably reliable, and the reason this is so is because:
Patients don’t know what their hands are supposed to do when dropped over their face and the idea of striking themselves is instantly unappealing. But what to do instead? The resulting dilemma is both revealing and, often, hilarious. The amusing nature of watching a conscious patient decide what to do with their falling hand is certainly part of the popularity of this exam.
However, he warns that there are patients who have "played the game before" and may be able to fake a convincing response even to the hand drop test. In an article on "Faking Unconsciousness"
in the journal Anaesthesia
(April 2000), the author noted:
During a ‘hand drop’ test, to my astonishment, I have caught the glimmer of a smile and realised that this patient knew too much. She had indeed read the literature.