Big Picture Group had a good idea: eight performers tell two stories each, one true and one false. After each tale, audience members vote on which they think it is. Forced to focus on why you believe something you're told, you realize it's because a story appeals to your prejudices or you want an aesthetically satisfying narrative to be real. The stories themselves--often tales about childhood, family, dating--are entertaining and well done, augmented by Big Picture's trademark video expertise. But the game goes on too long, approaching two hours, becoming monotonous. And a crucial step is left out: we're never told which stories are bogus, an omission that deflates the whole enterprise. --Laura Molzahn a Through 1/28: Thu-Sat 7:30 PM, Sun 2 PM, Viaduct Theater, 3111 N. Western, 773-539-7335, $10-$15.