导读：教室嚼口香糖被禁止由来已久，可是来自美国St Lawrence University 的新调查显示，学生在考试前嚼五分钟口香糖有助于提高成绩。这是为什么呢，一起看看新闻是怎么说的吧。
It has been banished from classrooms for decades.
But now it seems schools should be encouraging their students to chew gum, after a study found it boosted their performance in tests.
Researchers at St Lawrence University in Canton, New York, found those who chewed gum for five minutes before a test got better marks than those who didn't
The improvement was down to ‘mastication-induced arousal’ lasting for up to 20 minutes, according to researchers in the psychology department.
Previous studies have found that any physical activity boosts brain performance, but this proves even minor physical activity can do the same.
For the study, published in the journal Appetite, researchers looked at the effects of chewing gum on 80 undergraduate students.
Half of the subjects were given gum - both sugar-free and sugar-added - and chewed either prior to or throughout testing.
Pupils were then given a ‘battery of cognitive tasks’, such as repeating random numbers backward and solving logic puzzles.
Their results were then compared with subjects who did not chew gum.
While students who chewed gum for five minutes before a test achieved better scores on average, chewing during the test was found to have an opposite effect as it distracted the brain from its main task.
This may be due to ‘a sharing of resources by cognitive and masticatory processes,’ researchers, led by Dr. Serge Onyper, said.
The results define similar research carried out at the University of Northumbria in England in 2002.
At the time, one of the lead researchers, Dr Andrew Scholey, explained the positive effect of chewing gum on the brain.
'We don't think that it is anything in the gum, but that the resistance of the gum and the act of mastication that is making the difference,’ he said.
'We found an increase in the heart rate of five or six beats per minute when they were chewing gum.
'This may be unrelated to brain function, but on the other hand an increase in the blood delivery of oxygen to the brain may increase cognitive function.’