What truths does "truth serum" sodium pentothal actually reveal?

The famed chemical sodium pentothal, which is commonly known as truth serum, has been a mainstay of spy flicks for decades. In real life, scientists have tested it on spies, psychiatric patients, pregnant women, and suspected criminals. They all talked, but did they say something meaningful? Or was it just what the… » 4/19/12 9:00am 4/19/12 9:00am