Here's my guess...two interconnected mats, the one where we step, hold our breath, and hope for the 'lucky' arrow - and the other, over at the skinny-jean-test line. And rather like a see-saw, if the unlucky-line-mat is 'weighted', the hold-breath-mat will send you off for your 5 scotches. But if it's unoccupied, no relaxing for you...

Just a theory, completely unsubstantiated...but that's what it looked like was happening at YOW during the 'trial' phase.