ALBANY， New York - Students who rely on working at night to improve their grades might want to sleep on that strategy： a new survey in the US says those who never study all night have slightly higher grades than those who do．
A survey of 120 students at St． Lawrence University found that students who have never pulled an all-nighter have higher grades than those who have． The survey found those who did not study through the night had a grade point of 3.2 compared to 2.95 for those who have．
The study， by assistant professor of psychology Pamela Thacher， is to be included in the January issue of Behavioral Sleep Medicine．
"It's not a big difference， but it's pretty striking，" Thacher said． "I am primarily a sleep researcher and I know nobody thinks clearly at 4in the morning． You think you do， but you can't．"
Many college students， of course， have not enough or regular sleep， for reasons ranging from too much caffeine （咖啡因） to poor time management．
"A lot of students thought all-nighters were a very useful tool for accomplishing work， that caffeine intake was very useful in meeting deadlines and stuff like that，" said Mr Chatani， who had a 3.4grade point last term．
Dr Howard Weiss， a physician at St． Peter's Sleep Center in Albany， said the study results make sense．
"Certainly that data is out there showing that short sleep time absolutely influences concentration， influences performance on objective testing，" he said．
Some night owls do get good grades， of course， which may be explained by circadian rhythms （生理节奏）， Weiss said． Some people have different 24-hour body clocks than others， and may do better depending on class and testing times， Weiss said．



The purpose of the passage is to tell us ______ ．

A. all-nighters hurt students" grades
B. Thacher's doubt about all-nighters
C. the bad effects of pulling an all-nighter
D. pulling an all-nighter leads to sleep problems

According to Thachar's study， around 4 o'clock in the morning is a time when ______ ．

A. one can think more clearly
B. one has his/her best memory
C. one can't learn well
D. one's brain is more active

Which of the following is true？ ______

A. Not all night owls get bad grades．
B. Short sleep has nothing to do with concentration．
C. Caffeine intake is a useful way to accomplish work．
D. Chatani is a student who benefits from pulling all-nighters．

An all-nighter in the passage refers to ______ ．

A. a drink to keep people awake all night
B. a habit of accomplishing work at night
C. a person who falls into the habit of working at night
D. a way to improve one's grades by staying up late