“When the introverts were asked to work at the noise level preferred by the extroverts, and vice versa, everything changed. Not only were the introverts over-aroused by the loud noise, but they also underperformed—taking an average of 9.1 trials rather than 5.8 to learn the game. The opposite was true for the extroverts—they were under-aroused (and possibly bored) by the quieter conditions, and took an average of 7.3 trials, compared with the 5.4 they’d averaged under noisier conditions.”