但這個謎團被經濟學家陶德•斯坦布裏克納(Todd Stinebrickner)和他的父親、數學家拉爾夫•斯坦布裏克納(Ralph Stinebrickner)解開了 ((HC案：PDF] The Causal Effect of Studying on Academic Performance Todd ...))。
他們給一些學生隨機分配了一位擁有遊戲機的室友，然後借助詳細的時間使用問卷，對這些學生進行了考查。這些學生和他 們的室友在初始測試成績、喝酒或睡眠的時間等方面都沒有差別。但那些室友有視頻遊戲機的學生減少了學習時間，將更多時間花在玩《最終幻想12》(Final Fantasy XII)上。純粹的偶然——分配室友——似乎影響了學習的時間，不涉及其他任何重要決定。是的，這些學生的成績受到了影響。
My economics tutor says that I should be studying harder if I want to do well in my exams. I think that he is basing his advice on purely theoretical assumptions, and that there is no empirical evidence for his assertion. Who is right?
You're probably correct that his advice is not based on empirical research – not because no research exists, but because it is very recent. But I am sorry to report that his wild speculations have now been confirmed by an intriguing natural experiment.
Previous researchers have struggled to establish a causal link between exam results and time spent studying. That is not a surprise. Bright students might work harder because theyenjoy the work. Or failing students might cram to rescue their grades. Untangling the statistics seems impossible.
Yet the puzzle has been resolved by Todd Stinebrickner, an economist, and his father, mathematician Ralph Stinebrickner. Equipped with detailed time-use questionnaires, they looked at students who were randomly assigned a room-mate with a games console. Neither the students nor their room-mates differed in, say, initial test score, time spent boozing, or sleeping. But students whose room-mates had video games spent less time studying and more playing Final Fantasy XII. Pure chance – the assignment of a room- mate – seems to affect time spent studying, and no other important decisions. And yes, the grades suffered.
If the analysis is correct, an extra hour a day studying has a very substantial impact on test scores – enough to lift a typical student into the top third. Unless you know some very good computer games, that is likely to be a rational investment of your time