On this hour of Radiolab: a journey to the edge of human limits.

How much can you jam into a human brain? How far can you push yourself past feelings of exhaustion? We test physical endurance with a bike race that makes the Tour de France look like child’s play, and mental capacity with a mind-stretching memory competition. And we ask if robots--for better or worse--may be forging beyond the limits of human understanding.

We'd also like to honor the passing of one of our guests in this episode, Jure Robic. Lulu Miller, who interviewed Jure for this story, wrote a remembrance of Jure, and included some audio not featured in the episode. You can find that here. 

Correction: An earlier version of this piece stated in error that Mr. S. remembered what his editor had assigned all the reporters at the newspaper. In A.R. Luria’s book, there is mention only of Mr. S. remembering his own assignments. We also inaccurately stated the rate at which Mr. S. could recall numbers. The actual rate was 50 numbers in 2.5-3 minutes. We also incorrectly stated that Mr. S. memorized Dante's “Inferno.” In fact, Mr. S. memorized only the first several stanzas. In addition, we depicted details of Mr. S.’s mnemonic performances without making clear that they were based in part on supposition. The audio has been adjusted to correct these facts and clarify our suppositions.