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TED is dedicated to ideas worth spreading. And that leaves many wondering exactly which ideas have been spread the most widely in the six years that TEDTalks videos have been available online. Here, a list of the 20 most-watched talks on all the platforms we track: TED.com, YouTube, iTunes, embed and download, Hulu and more, as of November 2012.

From education to brain function to inspiring messages to techno-possibilities, this list represents quite a breadth of topics.

Compare and contrast how the 2012 list of the most popular talks stacks up to the 2011 list, written on the fifth birthday of TEDTalks videos.