经过一段时期的工作、学习 ,人的大脑会出现疲劳现象。出现时间的频率、长短 ,与人的年龄、健康状况、劳动、学习强度有一定关系。一般讲 ,小学生能保持注意力二十分钟左右 ,初中生四十分钟 ,高中生五十分钟 ,大学二小时。大脑疲劳表现为 :反应性下降 ,思考力降低 ,记忆力减弱 After a period of work, study, people’s brains will appear tired. The frequency of occurrence of the time, length, and people’s age, health status, labor, learning intensity has a certain relationship. In general, primary school students can keep their attention about twenty minutes, junior high school students forty minutes, high school students fifty minutes, two hours college. Brain fatigue as follows: decreased reactivity, decreased thinking, memory loss