Neuroscientists recently studied Honnold’s brain. They put him in a large machine and then quickly showed him a series of terrifying and off-putting images — toilets overflowing with faeces, mangled and bloody faces, a climber dangling over the void — the sort of stuff that would send most people shivering, gagging, or both.

It didn’t register with Honnold. They hadn’t seen anything like it. His amygdala, the part of the brain that reacts to fear, lay dormant.

“Maybe his amygdala is not firing — he’s having no internal reactions to these stimuli,” said neuroscientist Dr. Jane Joseph. “But it could be the case that he has such a well-honed regulatory system that he can say, ‘OK, I’m feeling all this stuff, my amygdala is going off,’ but his frontal cortex is just so powerful that it can calm him down.”