Can you remember who your best friend was in seventh grade? If you are having difficulty, it could be because relationships at that age are often short-lived. Half don't last a year. The friendships that do last can be predicted based on demographic and behavioral similarities, according to new research from psychologist Brett Laursen of Florida Atlantic University.
你还记得七年级时最好的朋友是谁吗？如果你想不起来，那可能是因为那个年纪的友谊通常都难以延续。半数的友谊都不会超过一年。佛罗里达大西洋大学的心理学家布雷特·劳尔森发布的一项新研究显示，长久维系的友谊可以通过人口学统计数据和行为相似性这两方面预知。

“There is a lot of change during middle school, and that change makes it hard to maintain friendships,” Laursen says. As kids move from one academic track to another, join or leave sports teams, or take up new extracurricular hobbies, the opportunities to interact with friends wax and wane. Middle school is also a time when growing personal autonomy first allows children the chance to pick their friends and invest—or not—in those relationships.
劳尔森称：“中学时期会有很多变化，而那些变化会使得人们难以维持一段友谊”。当孩子们从一个学习阶段步入另一个学习阶段，参加或离开体育队，或是有了新的课外的兴趣爱好，那么，和朋友在一起互动的机会就会此消彼长。中学也是孩子们自主能力逐渐增强的时期，孩子们有机会自己选择朋友，或是决定是否要在这些关系上进行“投资”。

Laursen tracked 573 seventh-grade two-person friendships until they ended or until 12th grade. A few important behavioral traits emerged as predictors of friendships that lasted more than a year: popularity, aggression and academic success. The more similar two friends were in these traits, the longer a relationship lasted.
劳尔森跟踪了573对七年级的友谊关系，到第十二个学年结束或是持续到第十二个学年。其发现了一些预示着友谊关系持续一年以上的重要的行为特征：知名度、上进心、和学业成绩。两个朋友在这些特征上越相似，友谊关系将维持地越长久。

Friends of the opposite sex were least likely to last. “They're completely doomed,” Laursen says, in part because of pressure from other friends. Adolescents tend to sort themselves based on age, race and gender, so being friends with a member of the opposite sex limits the size of one's larger group of “running buddies” and taxes the relationship.
异性朋友之间的关系维持下去的可能性最小。劳尔森称：“他们注定是要终结的”，部分原因可能是来自于其他朋友的压力。青少年倾向于将朋友按年龄、种族和性别等因素予以分类，因此，和异性交朋友会限制自己扩大“同类好朋友”朋友圈，并且会给此种友谊造成负担。