Do friends of the opposite gender distract teenagers,hampering their academic performance?It may seem obvious,and yet it is hard to prove.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.A new paper by Andrew Hill of the University of South Carolina,however,comes to a different result.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 O.l（GPAs range from O t0 4）.Not only may having more friends of the opposite sex be bad for grades,but it has other effects,too.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 married.
交异性朋友会使青少年分心，影响他们的学业吗？这个问题看似显而易见，但其实很难证实。比如．1995年，对美国在校儿童的一项调查显示：女生的学业成绩与其异性朋友的所占比例无关。然而，南卡罗采纳大学的教授Andrew H．1l发表的最新论文却得出了不同的结论。他发现，一个学生的朋友中，每多IO%的异性朋友，他或她的各科平均绩点（GPA）会下降O.l（各科平均绩点在0-4之间）。交更多的异性朋友不仅不利于学业，还有其他一些影响。14年后，对初次参加调查的孩子又进行了一次采访，结果显示，因交异性朋友而导致成绩下降的孩子更可能结婚。
