How to get people to tank!

[Zojha]

All research into learning shows just the opposite. People learn better when they're under stress [...]

Mhm...briefly skimming over some journal abstracts and conclusions, the findings actually seem quite torn. The only unambiguous results seem to be that chronic, extreme and early childhood stress can damage the hippocampus and have long-lasting detrimental effects on learning and memory processes.

In mice/rats, I found some findings on an inverted U-function and individual differences.
http://learnmem.cshlp.org/content/17/10/522.short

Seems to be mostly a:"It depends!" sorta thing.