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Finance and economics: Distracted teens The dreamboat next door
財經：分心的青少年，鄰家夢中人
It's official: having friends of the opposite sex is bad for children's grade.
官方數據顯示：與異性交朋友不利于孩子的學業成績。
Do friends of the opposite gender distract teenagers, hampering their academic performance?
與異性交朋友會使青少年分心，影響學業成績？
It may seem obvious, at least to paranoid parents, and yet it is hard to prove.
至少對多疑的家長而言這似乎顯而易見，但證明起來很難。
Simple analysis of a survey of American schoolchildren conducted in 1995, for example, suggests no link between the proportion of a girl's friends who were boys and her grades.
比如，對1995年美國在校兒童一項調查的簡單分析表明：女生的學業成績與其異性朋友的比例無關。
Boys with lots of female friends actually achieved better results than those with fewer.
實際上，相較于異性朋友少的男生，異性朋友多的成績更高。
A new paper by Andrew Hill of the University of South Carolina, however, digs deeper into the data, and comes to a different result.
然而，南卡羅來納大學的助理教授安德魯·希爾發表的最新論文深入分析了這些數據，得出了不同的結論。
Friendship groups are not random, which makes it tricky to isolate the effect of fraternising with the opposite sex on school performance.
朋友圈的非隨機性使得單獨考慮異性友誼對學業成績的影響十分困難。
Pushy parents, for instance, may both encourage after-school activities (hotbeds of hobnobbing across the gender divide) and help out with homework.
例如，望子成龍的父母可能既鼓勵課外活動（異性間親密接觸的溫床）又贊同幫助解決家庭作業中的難題。
By the same token, the sort of boys who do not find it embarrassing to join a clique composed mainly of girls may also be more studious.
同理，不會因加入以女生為主的小團體而感覺難為情的男孩也更加好學。
Mr Hill gets around this by looking at the proportion of schoolmates of either sex living near each student.
為了解決上述問題，希爾將目光投向每位同學鄰居中男女同學的比例。
He reasons that parents do not choose where to live based on the sex of their neighbours' children.
他推斷父母不會以鄰居家孩子的性別作為選擇居所的標準。
The gender mix of near-neighbours should therefore be unrelated to the invisible factors that influence both friends and grades.
因此鄰居家孩子的性別構成也應該與影響朋友和成績的隱性因素無關。
But the mix of neighbours does influence friendship groups in school, since children are much more likely to befriend other children who live close by.
但是鄰居間孩子的性別構成確實影響學校中朋友圈的形成，因為孩子們更傾向與住得近的孩子交朋友。
Mr Hill calculates the share of boys and girls among each child's 20 closest neighbours and uses this to identify random differences in friendship groups.
希爾先生計算了每個兒童20個最親密的鄰居中男女孩的比例并用上述計算結果確定了朋友圈的隨機差異。
He can then isolate the effect of having more friends of the opposite gender on school performance.
他排除了學生交更多異性朋友對其學業成績的影響。
He finds that for every 10% more children of the opposite sex among a student's friends, his or her grade-point average (GPA) declines by 0.1 (GPAs range from 0 to 4) .
他發現一個學生的朋友中每多10%的異性朋友其各科平均績點（GPA）會下降0.1(各科平均績點從0~4)。
Below the age of 16, the effects are restricted to science and maths, but beyond 16 they spill over to English and history as well.
這種影響在16歲以下僅限于科學和數學，但是在16歲以上會波及到英文和歷史。
Girls seem to be more prone to distraction, though Mr Hill cannot muster the statistical power to be certain.
盡管希爾先生沒有搜集到確鑿的統計數據，但是女孩子似乎更容易分心。
This tentative result is consistent with other studies that find that girls gain more from moving to single-sex schools.
這種不確定的結果與其他研究一致，這些研究都表明，轉到女子學校上學的女孩子將學到更多。
Readers rushing to remove their children from co-ed schools should know, however, that Mr Hill's results came with a twist.
然而，那些匆忙讓自己孩子從男女同校轉走的家長應當了解：希爾先生的結論有個意外發現。
Having more friends of the opposite sex may be bad for grades, but it has other effects, too.
交更多的異性朋友可能不僅不利于學業成績，還有其他影響。
Among the children from the original survey who were successfully re-interviewed 14 years later, those whose grades had been dragged down by friends of the opposite gender were more likely to be (or have been) married.
在那些14年后順利再次會面的參加初次調查的孩子中，因交異性朋友而成績下降的孩子更可能（或已經）結婚。
Traditionalists worried about a child mooning over the heartthrob next door may comfort themselves with that.
傳統主義者擔心癡想鄰家夢中情人的孩子以此來安慰自己。
譯文編自AuroraW
