There are at least a few in every college dorm: students who seem to exist in their own time zone, in bed hours before everyone else and awake again at daybreak, rested and prepared for the morning's first lecture.

    Sleep researchers refer to these early risers as larks （midnight-oil-burners are known as owls）, and new data presented this week at the annual Associated Professional Sleep Societies suggest that a student's preferred sleeping schedule has a lot to do with his or her grade-point average in school. In one study, psychologists at Hendrix College in Arkansas found that college freshmen who kept night-owl hours had lower GPAs than early birds. Another group at the University of Pittsburgh revealed that poor sleep habits among high-schoolers led to lower grades, particularly in math.

    It's no surprise that poor sleep habits may negatively impact academic performance - anyone who's been exhausted enough to doze off during class knows that's detrimental to learning. And dozens of studies have linked an increase in nightly sleep to better cognition and alertness. The new research, however, goes a step further, quantifying the impact of erratic or inadequate sleep on grades. "These findings are more tangible than saying that if you get more sleep, you'll feel better," says Jennifer Cousins, a fellow at the University of Pittsburgh and author of one of the studies. "They connect sleep and how you sleep to the real world of daily activities."

    In the study of night owls, psychologist Jennifer Peszka asked a group of 89 incoming Hendrix College freshmen ages 17 to 20 to fill out a questionnaire about their sleep preferences prior to arriving on campus. Regardless of how much they actually slept, Peszka asked them whether they considered themselves owls, larks or, in the case of those who were neither very late or very early sleepers, robins. Students also answered questions about their sleep "hygiene" - factors that contribute to quality of sleep, such as adhering to a regular bedtime, waking up at the same time every day, or exercising or drinking caffeine before trying to sleep. One year, Peszka asked the same students to fill out another similar questionnaire to determine whether their sleep schedules were associated with GPA.

    The owls, it turned out, averaged a 2.84 GPA at the end of their freshman year. Larks and robins both averaged 3.18. That means high-quality sleep may have contributed to one group of students' B average, while inadequate shut-eye pushed owls into the C range. Peszka also compared the students' high school GPAs with their college scores, and found that owls had lost an entire GPA point once entering college - larks and robins also saw their grades drop （a common phenomenon as students transition from high school to university）, but not as much. "Not only did they flat out have a lower freshman GPA," she says of the owls, "but they also dropped their grades more."

    The study did not delve into the details of why owls may perform worse in school, but Peszka suspects it may boil down to "an owl living a lark's schedule." Students with late bedtimes still end up taking early morning classes, which means they often end up feeling sleepier and less alert during the day. In fact, in Peszka's study, night owls slept 41 minutes less each night than the other students, but were still attending early classes, during which they reported sleepiness and inability to concentrate, which, unsurprisingly, led to lower scores at exam time.

    That's precisely what University of Pittsburgh researchers found in their study of 56 teens ages 14 to 18. Jennifer Cousins, a postdoctoral fellow in psychiatry, asked the adolescents to fill out sleep diaries for one week and wear a special activity monitor on their wrist, which recorded when the students were asleep or awake. Overall, teens with poor sleep habits - those who woke up frequently during the night, spent more hours in bed （whether or not they were sleeping） and reported feeling tired in the morning - received lower grades than students who stuck with a more regular sleep routine.

    Interestingly, Cousins also found that different sleep habits had different effects on the student's school performance: those who woke up more often during the night and reported poorer sleep quality did worse in math, for example, while those who slumbered peacefully through the night tended to get better grades in English. "These findings bring up new questions about teasing out the specifics of what is important about sleep that impacts learning," says Cousins. "Does sleeping more help our ability to deal with abstract concepts found in math, or does sleep quality increase creativity? We don't know the answers, and don't want to draw those conclusions yet. But this helps us understand more about how sleep helps the things we do in daily life."

    Both groups of researchers are quick to point out that academic performance is the product of many different factors - from I.Q. to study habits and effort, and not just sleep - but the new findings suggest that catching good quality z's certainly doesn't hurt, and may even help boost your GPA.

    在大学宿舍都至少有一小撮学生：他们似乎生活在自己的时区，在其他人上床前几小时就睡觉然后在黎明醒来，休息一下并准备上午的第一堂课。

    睡眠研究人员提及这些早起的人称他们为"云雀"（最能熬夜的午夜燃烧器是猫头鹰）,最新的发表在这周的《年度相关专业睡眠协会》的数据表明：学生首选的睡眠时间表与他或她在学校的平均学分积有很强的相关。在一项研究中，阿肯色州里克斯学院的心理学家发现，大学新生中那些"夜猫子"式的作息方式的学生们比早起的"云雀"平均学分积低。另一组美国匹兹堡大学的研究发现，高中学生劣质的睡眠作息方式导致较低的学习成绩，特别是数学成绩。

    毫不奇怪，劣质的睡眠作息习惯会对学习成绩产生不利的影响。那些已经累到在课堂上打盹的人都知道，这样对学习很不好。其他几十个研究表明夜间睡眠时间的增加与更好的认知和警觉感觉相联系。然而，这项新的研究更进了一步，它量化了睡眠的影响，探索了不稳定或睡眠不足对于学习成绩的影响。"比起那些空洞的说法说：如果你获得更多的睡眠，你会感觉更好。这些调查结果更为具体。"詹妮弗。卡曾斯说。他们将睡眠和你在现实世界的日常活动中如何睡眠联系起来。

    在对那些"夜猫子"的研究中，心理学家詹妮弗。佩兹卡让来自里克斯大学89名17-20岁的大一新生填写了一张问卷调查他们在进入大学之前的睡眠偏好。无论他们自己的睡眠偏好如何，詹妮弗都会让他们自己评价自己认为自己是"夜猫子","云雀",还是睡得不早也不晚介于中间角色的"知更鸟".大学生们还回答了关于自己睡眠的"卫生"--影响睡眠质量的因素，比如坚持固定的上床时间，每天同样的时间点起床，在睡前运动，喝咖啡等等。一年之后，佩兹卡让他们再填写相同的问卷，以此来考察他们的睡眠时间表与平均学分积是否相关。

    研究表明，那些"夜猫子"们，在他们的大一学年末有2.48的平均学分积；而"云雀"有3.18的平均学分积。这表明高质量的睡眠很可能对学生B的平均学分积有贡献。佩兹卡同时还对比了那些学生在高中时候的学分积，发现那些熬夜的"猫头鹰"们自从进入大学之后平均学分积下降了一个积点--"云雀"和 "知更鸟"的学分积也都有下降（这是学生从高中到大学的普遍情况）,但不会有这么多。"他们的成绩不仅低于新生的平均水平，"她说，"而且他们的成绩下降更多。"

    这项研究并没有深入研究为什么夜猫子在学习成绩上的表现差的细节。但佩兹卡怀疑原因可以归结为"夜猫子"仍然按照"云雀"的时间表生活。那些晚睡的学生仍然早起上课，这意味着他们最终往往在白天感觉很困倦，警觉性降低。事实上，在佩兹卡的研究，"夜猫子"比其他的学生们每晚少睡41分钟，但仍早起上课，在此期间，意料之中地，他们报告嗜睡和精神无法集中，这些都导致考试期间较低的分数。

    这恰恰是美国匹兹堡大学的研究人员在对56位14岁至18岁的少年们进行研究发现的。詹妮弗。卡曾斯--心理咨询的博士后人员，要求青少年填写为期一周的睡眠日记，并要求在他们手腕上带上特殊的活动监测器，记录时学生们入睡或醒来的情况。总之，具有较差的睡眠习惯的青少年--那些在夜间睡眠时经常醒来，花很多时间赖在床上（不管它们是不是睡眠）和在早晨报告感觉疲累--获得的成绩比那些坚持规律睡眠的学生更低。

    有意思的是，卡曾斯发现不同的睡眠习惯对学生们的成绩表现有不同的影响：那些在睡觉时经常醒来并报告睡眠质量很差的学生在数学表现不好，而那些在整个晚上睡得很平静的学生容易获得更好地英语成绩，"这些发现带来了新问题，那就是关于具体厘清影响学习的睡眠哪个过程是重要的？"卡曾斯说道，"睡眠是否对于我们处理在数学中的抽象问题更为有益？或者睡眠质量是否增加了创造性？我们不知道这些问题的答案，而且我们还不想下定论。但这些帮助我们对睡眠在日常生活中对哪些事情有益有更多的了解。"

    这两组研究人员正在迅速指出，学习成绩是许多不同的因素共同作用的结果--从智商学习习惯和努力程度，而不仅仅是睡眠--但新的研究结果表明，追求优质的睡眠肯定没有坏处，甚至可能有助于提高您的成绩。