The trick --
not that I've had personal experience with this, so quit looking at me like that -- is to slow the rate at which the water drips until the lucky contestant can almost -- but not quite -- predict when the next drop will fall. A deliciously dreadful sense of expectation builds up --
"...willitfall? whenwillitfall? itshouldhavefallenbynow? whywon'titfall? howlonghasitbeen? amIlosingmymind? pleasefall,prettywaterdroplet. please. I'llbegood. pleasefall. whywon'titfall?..."
-- only to be replaced by immense shock and relief when it finally does...and the cycle immediately begins anew. The tantalising release of tension prevents the subject from withdrawing too far inside themself (as with prolonged torture by Western and other Chinese methods) yet is too brief to allow them to locate themself outside the world the torturer has built for them (because the torturer does not need to rest, and pauses to assess physical damage are unnecessary; we are NOT in the business of
execution here, peoples).
Guaranteed to get your mind whitey-white, or your money back.