Psychology
A little stress sharpens performance; too much wrecks it
In 1908, Robert Yerkes and John Dodson found mice learned a maze fastest under moderate electric-shock stress — too little left them unmotivated, too much made them frantic and error-prone. Performance traces an inverted U: it rises with arousal up to a point, then collapses. A little pressure before a talk helps; too much wrecks it.