請您讀一遍下面的一行隨機數字：
然後合上書，按照原來的順序，儘可能多地默寫出來。
現在再讀一遍下面的隨機字母：
HJMROSFLBTW
然後用上述相同的方法來測試自己的記憶.
測測你自己
假如你的短時記憶像一般人那樣,你可能回憶出7個數字或字母,至少能回憶出5個,最多回憶出9個,即7±2個。
這個有趣的現象就是神奇的7±2效應。這個規律最早是在19世紀中葉,由愛爾蘭哲學家威廉•漢密爾頓觀察到的。他發現，如果將一把子彈撒在地板上，人們很難一下子觀察到超過7顆子彈。
1887年，雅各布斯通過實驗發現，對於無序的數字，被試能夠回憶出的最大數量約為7個。發現遺忘曲線的愛賓浩斯也發現，人在閱讀一次後，可記住約7個字母。這個神奇的「7」引起許多心理學家的研究興趣，從20世紀50年代起，心理學家用字母、音節、字詞等各種不同的材料進行過類似的實驗，所得結果都約是「7」。
1956年，美國心理學家米勒（George A. Miller）教授發表了一篇重要的論文《神奇的數字7加減2：我們加工信息能力的某些限制》，明確提出短時記憶的容量為7±2，即一般為7並在5~9之間波動。這就是神奇的7±2效應。
但是實驗中採用的材料都是無序的、隨機的，如果是熟悉的字詞或數字，這樣短時記憶還只能容納「7」個嗎？
例如「c-o-o-p-e-r-a-t-i-o-n」,這個字母序列已經有11個字母，如果學過英語的人聽到這個序列很快就能明白這是個詞，意思是「合作」，並能很好地回憶出來，這不是違背了短時記憶的「7±2」效應了嗎？不是的，這恰恰是神奇「7±2」存在的另一個奇特的現象。
因為短時記憶中的信息單位「組塊」本身具有神奇的彈性，一個字母是一個組塊，一個由多個字母組成的字詞也是一個組塊，甚至可以通過一些方法把小一些的單位聯合成為熟悉的、較大的單位，而且對知識的熟悉程度還會對它產生影響。例如「認知心理學」5個字對於不懂心理學的人來說是5個組塊；對稍懂心理學的人來說是兩個組塊（認知、心理學）；而對專業心理學學生、心理學家來說這5個字就只有一個組塊。但不論人們儲存的組塊是什麼，短時記憶的容量為7±2個組塊。
「電錶」的功能
神奇的7±2效應給我們最直接的啟示就是，短時記憶的容量是有限的，不要再幻想一口吃一個胖了，一下子變天才。短時記憶就像一個家庭電錶，如果同時開的電器過多，那麼只能把保險絲燒掉。不管是學生給自己設定學習目標和計劃時，還是教師進行授課時，就要考慮到7±2的特點合理安排學習任務，否則就會像電力超載一樣，出現認知超載！
小明有一個苦惱，不知道你能不能幫忙解決。小明總是抱怨自己的背誦能力很差，往往一大篇詩詞會越背越亂，後來不但前後左右都搞不清楚，而且還會把不相干的兩首詩拼湊起來，前頭是唐詩，後面接宋詞，簡直是一團糟。
張老師班裡的同學可沒有小明那麼苦惱，張老師的課總是妙趣橫生，課後學生總是能清晰地記住並理解所有的內容，寫作業也不再是苦差事。
細心觀察，其實都是短時記憶的容量作為「看不見的手」來導演的好戲。小明的問題就是一下子把記憶的電力開得太足了，後果只能越背越亂。而張老師在課堂內容編排上深諳其道，他早已摸清了自己學生的先前知識，於是每堂課都保證給學生的新內容不超過7個。
就這樣，不管是學習課文還是呈現幻燈片，張老師給學生的學習任務都不超過7個，於是學生學得容易，學得有意義。現在想必你孔已經有了解決小明問題的方法，那就是短背比長背好，把長的內容切成合適的知時記憶的分量來背誦，然後再通過組合的技巧將各個段落接在一起，就可以記下一段長篇的完整內容了。遵循短時記憶的運轉之道，問題自然會迎刃而解。
超越7±2
這個神奇的7±2，不僅給我們打開了認識記憶的窗戶讓我們了解了短時記憶的限制，還給我們指出了提高記憶力的好辦法。
讓著名的長跑運動員S.F.給我們做個範例，他可以一下子記住84個數字！
這都是因為S.F.經過煅煉，發現了一個對他非常有效的組合數字的方法！他根據自己職業特點，注意到了很多的隨機數字能被組織成不同距離的賽跑時間，於是產生了讓人驚嘆的神奇紀錄。
例如，他將數字序列3、4、9、2、5、6、1、4、9、3、5重新編碼為3：49。2，接近一英裡賽跑記錄；56：14，10英裡時間；9：35，對2英裡的距離而言時間有點長。
也就是說，如果能找到一些辦法將大量可用的信息組成少量的組塊，自己記憶的廣度將會大大增加；通過專門訓練，人的短時記憶容量可以擴大。
就像S.F.一樣，你也可以根據信息對你個人的意義對它進行組織（例如，將電話號碼與親戚朋友的生日相聯繫）；或者還可以採用一種節奏模式或者時間模式來對項目進行簡單的組織，例如我們記憶和機號碼時往往會採用3個或者4個一組來記憶，1369停頓，再繼續下面的號碼。
不僅如此，節奏模式還對評議有著很好的組織作用，有一個學音樂的人，他把與別人的談話當作了一種節奏，按照這種節奏來理解別人的意思，成為一個非常優秀的推銷員。或者還把記憶任務賦予意義，例如「7-4-7」記作「波間音747客機」，或將「7-14-4」記作「電話查號臺」，以便在短時記憶中很好地處理信息。
這些方法對你有用嗎？再加有過之而無不及頭看「記憶超群」，是否已經不再是什麼神話？對，只要你有好的記憶方法！倫敦學院大學的馬格裡（Eleanor Maguire）教授的研究也證明了這一點。
他與同事對普通人和那些被倫敦世界記憶錦標賽列入記憶力最強的人進行了比較。除了具有更強的記憶能力，採用了符合自己的記憶方法，記憶超群者在語言和非語言的綜合測試中與普通人沒有差別；磁共振成像技術（MRI）測試也表明，他們的大腦結構與常人沒有明顯差異。
可見短時記憶這個「電錶」的容量也不是絕對的，我們在遵守它的運轉法則的基礎上，如果能靈活地利用各種方法來劃分短時記憶的組塊，不僅能提高自己的記憶能力，而且可以減輕記憶的壓力，省出更多的空間和精力來處理更有意義的思考任務，使你自己變成一個有效率的學習者或教學者。
英文版：
Please read the following line of random Numbers:
Then close the book and write as much as you can in the original order.
Now read the following random letters:
HJMROSFLBTW
Then test your memory in the same way.
Measure yourself
If your short-term memory is like the average person, you might recall seven Numbers or letters, or at least five of them, and recall up to nine, or seven or two.
This interesting phenomenon is the magic 7 + 2 effect. The law was first developed in the mid-19th century by the Irish philosopher William. Hamilton observed. He found that it was hard to see more than seven bullets in one shot if a bullet was placed on the floor.
In 1887, jacobs found that the maximum number of unordered Numbers was about seven. He also found that people can remember about seven letters after reading one. This mysterious "7" caused many psychologists study interest, since the 1950 s, psychologists use a variety of different materials such as letters, syllables, words, conducted a similar experiment, the results are about "7".
In 1956, the American psychologist professor Miller (George a. Miller) published an important thesis "the magic number seven and subtract 2: some limitations of our processing information ability, specifically to short-term memory capacity of 7 + 2, which is commonly 7 and swings between 5 ~ 9. This is the magic 7 + 2 effect.
But the materials used in the experiment are disordered and random, and if they are familiar words or Numbers, can the short-term memory only contain "7"?
Such as "c - o - o - p - e - r - a - t - I - o - n", the letter sequence has 11 letter, if you learn English people hear the sequence will soon be able to understand that this is a word that means "cooperation", and a good memory, it is not against the "7 plus or minus 2" short-term memory effect? No, this is just another curious phenomenon of the magic "7 plus or minus 2".
Because the information in the short-term memory unit "chunking" itself has the magic of elasticity, a letter is a group of block, by many letters of a word is also a set of blocks, even by some methods to smaller units joint become familiar, larger units, and the familiarity of knowledge will affect it. For example, "cognitive psychology" 5 words for people who don't know psychology are 5 blocks; For people who understand psychology, there are two groups of blocks (cognition, psychology); For professional psychology students, psychologists say there is only one block. But no matter what the group is stored in, short-term memory has a capacity of 7 plus or minus 2 blocs.
The function of "electricity meter"
The magic 7 + 2 effect gives us the most immediate implication that short-term memory capacity is limited, and don't fantasize about eating a fat one at a time. Short-term memory is like a home meter. If you have too many appliances at the same time, you can only burn the fuse. Whether students set learning goal and plan for themselves, or when teachers teach classes, is considering the characteristic of 7 plus or minus 2 reasonable arrangement of learning tasks, or you will like electrical overload, a cognitive overload.
Xiao Ming has a problem. I don't know if you can help with it. Xiao Ming is always complaining about their ability to recite is very poor, often a large piece of poetry will back more and more disorderly, later all around not only don't know, but also the irrelevant two poems together, front is the tang dynasty, followed by song ci, it is in a mess.
Teacher zhang's class can not as distress, xiao Ming zhang teacher's class is always interesting, after class, students can always clearly remember and understand all of the content, homework is no longer a drudgery.
Careful observation is actually the capacity of short-term memory as the "invisible hand" to direct the drama. The problem with xiao Ming is that the power of memory is too much, and the consequences can only be more and more messy. Mr. Zhang, who is well versed in the content of the class, has long understood the prior knowledge of his students, and has promised to give no more than seven new contents to his students every class.
In this way, no matter whether to study the text or present the slide, zhang has no more than seven learning tasks for students, so students learn easily and make sense. It must hole you already have the method to solve the problem of xiao Ming, that is good short back than long back, cut the long content into the appropriate knowledge memory component to recite, and then through the combination of skills to connect each paragraph together, can take a long full content. By following the way of short-term memory, the problem will be solved.
Beyond 7 plus or minus 2
This magical 7 + 2 not only opens up the window for us to learn about memory, but also gives us a good way to improve our memory.
Let the famous runner S.F. give us an example, he can remember 84 figures at once!
This is because S.F. has been calcined and found a way to make a very effective combination of Numbers! Based on his own professional characteristics, he noticed that a lot of random Numbers could be organized into RACES at different distances, resulting in amazing magical records.
For example, he recode the number sequence 3, 4, 9, 2, 5, 6, 1, 4, 9, 3, and 5 to 3, 49. 2. Close to a mile race record; 56:14, 10 miles; 9:35, it's a little long for two miles.
In other words, if you can find some way to make a small amount of available information, the breadth of your memory will increase greatly. Through specialized training, people's short-term memory capacity can be expanded.
Like S.F., you can organize your personal meaning based on information (for example, connecting your phone number to a friend's birthday); Or you can also use a simple rhythm mode or time to projects for the organization, such as our memory and machine number tend to use 3 or 4 a group to memory, 1369 pause, and then continue to the following number.
Not only that, the rhythm pattern also has a very good organization effect on review, people with a learning music, he had to talk with others as a kind of rhythm, according to this rhythm to understand the meaning of others, be a very good salesman. Or to give meaning to memory tasks, such as "7-4-7", or "7-14-4" as "telephone directory," to handle information well in short - term memory.
Do these methods work for you? Is it no longer a myth that there is no more than a little bit of "memory supergroup"? Yes, as long as you have a good memory method! Research by professor Eleanor Maguire of the university of London has also proved this.
He and his colleagues compared ordinary people with those who had the strongest memory of the London world memory championship. In addition to the stronger memory ability, using the memory method that conforms to oneself, the memory supergroup is not different from the ordinary people in the comprehensive test of language and non-language; Magnetic resonance imaging (MRI) tests also showed no significant differences in brain structure.
Visible short-term memory capacity of the "meter" is not absolute, we abide by the laws of its operation, if can be flexibly used various methods to differentiate short-term memory block, can not only improve their memory ability, and can reduce the pressure of a memory, save more space and energy to deal with more meaningful thinking tasks, make yourself a efficient learners or teaching.