Their task was simple: keep your eyes on the road; keep a safe difference; brake as required. If they failed to do so, they’d eventually collide with their pace car.
Then came the multitasking additions. They would have to not only drive the car but follow audio instructions from a cell phone. Specifically, they would hear a series of words, ranging from two to five at a time, and be asked to recall them in the right order. And there was a twist. Interspersed with the words were math problems. If they heard one of those, the drivers had to answer “true,” if the problem was solved correctly, or “false,” if it wasn’t. They would, for instance, hear “cat” and immediately after, “is three divided by one, minus one, equal to two?” followed by “box,” another problem, and so on. Intermittently, they would hear a prompt to “recall,” at which point, they’d have to repeat back all the words they’d heard since the last prompt. The agony lasted about an hour and a half.