Think for a moment: Is it true that "Duck Quacks Don't Echo"? This 2014 National Geographic series examines that assertion and a host of other brain-teasing hypotheses, through the employment of fascinating scientific experiments. You'll have plenty to consider as these unusual questions and theories are tested by some original thinking! Six-disc set also includes the three episodes from the first season of "Brain Games" and three episodes from "The Numbers Game." 10 hrs. total. Widescreen (Enhanced); Soundtrack: English.