Do you remember what you had for dinner two weeks ago? Now choose your favorite trip from a couple of years ago. How much do you remember from that trip? The chances are that you do not remember what you had for dinner but you do remember something about your trip, although it took place much earlier than the meal. This example shows that forgetting is not simply memories decaying with time. Our memories crucially depend on cues. A cue is essentially anything (such as a physical object, situation, time period, word, question, concept, etc.) which is paired with a memory trace and which must be activated for the memory trace to be retrieved. If we pair the same cues with multiple memory traces then it will be difficult to retrieve one particular trace because once the cue is activated, the activation will spread to all paired memory traces at once and these will compete for entry to consciousness. Coming back to the example above, if you usually dine in the same place, many different meals will become associated with the same cues (the dining environment). Therefore, it will be hard to retrieve the specific meal that you enjoyed a week ago. In contrast, you probably have not been on the same trip many times before, therefore it is easier to remember its details because they context of the trip is not paired with any other memories. The disruption of memories by other memories which are paired to the same cues is called “interference”. You may have experienced interference yourself if you ever studied a second language. Interference may have caused you to be unable to retrieve vocabulary from one language. Instead, vocabulary from the other language popped to your mind. In this case, interference did not necessarily cause a loss of memory, but the memory trace became blocked thus temporarily inaccessible. Research has found that the only way to overcome blocking interference is by making conscious effort to recover the correct memory trace (and have patience as this may take some time). Interference may, however, also cause a permanent loss of memory. Scientists who study memory call this the retrieval-induced forgetting effect (RIF). As a demonstration, consider the following experiment: Students studied 10 geographical facts about each of 2 islands (A and B). They subsequently practiced retrieving 5 out of 10 facts for island A. Afterwards, their knowledge of these facts was tested. What do you think happened to students’ memory about island A? Unsurprisingly, retrieval practice boosted retention for the 5 facts that were practiced (the percentage of correct answers was greater than for island B). However, it also worsened the memory for the 5 facts about island A that were not practiced (again compared to island B). What caused this effect? The island A serves as the context cue for information about island A, whereas island B serves as the context cue for information about island B. When the 5 facts about island A were retrieved from memory, their connection with the context cue was strengthened and the connection of the remaining 5 facts with the context cue was weakened (see “Testing effect”). The main implication of this study for learning is that selective practice testing substantially boosts performance for the practiced items but can also worsen the performance for the unpracticed items. How can we combat forgetting caused by interference? One way we can overcome interference is by making it explicit. If there are concepts that you get mixed up frequently then put them side by side and re-study them at the same time. The general idea is that whatever you are studying, it is good practice to make different concepts as distinctive as possible. This forces your brain to encode them as dissimilar memory traces. You can achieve this by stressing the differences between different concepts from your study material (by comparing and contrasting, for instance). Another effective strategy is to integrate the concepts. For instance, if you are memorizing the members of a particular animal/plant family, then try to find all possible relations between the members. When you're later retrieving these members, they will no longer compete for access to consciousness as they will be encoded closely together in an integrative manner. Instead of one concept blocking the other, they will be retrieved simultaneously. Scientists have found that our study goals also impact on how well we overcome interference. Students who focus on comparative performance (how well they do compared to other students) tend to use superficial processing (do not look for relations among concepts), whereas students who aim for mastery tend to use more deeper processing, such as establishing connections between different concepts. In summary, we recommend the following: ·Re-study concepts that you confuse –Use comparing and contrasting to find differences between the concepts –Integrate the concepts (find the relations between them) ·Aim for mastery in a subject, do not pay attention to other people's performance ——節(jié)選自《記憶的科學(xué)》
你還記得兩周之前的晚飯吃的什么嗎?現(xiàn)在從之前幾年挑選你最喜歡的一次旅行,你還記得多少?很可能你已經(jīng)不記得晚飯吃了什么,但能清楚地回憶起旅途中發(fā)生的事情,盡管它發(fā)生的時(shí)間比兩周前的那頓飯?jiān)绲枚唷?/p>
這個(gè)例子表明,遺忘并不僅僅是記憶隨時(shí)間消退。我們的記憶非常依賴線索。線索本質(zhì)上可以是與一段記憶痕跡相對應(yīng)的任何東西(例如一個(gè)實(shí)體物品、一個(gè)情境、一段時(shí)間、一個(gè)詞、一個(gè)問題、一個(gè)概念等等),只有先啟動(dòng)線索,才能檢索到對應(yīng)的記憶痕跡。
如果我們給同一個(gè)線索匹配了多個(gè)不同的記憶痕跡,那么將很難檢索到特定的某個(gè)痕跡,因?yàn)楫?dāng)線索被激活時(shí),激活信號(hào)會(huì)立刻傳播到所有對應(yīng)的記憶痕跡,它們相互競爭,看誰能夠進(jìn)入顯意識(shí)。
回到上面的例子,如果你經(jīng)常在同一個(gè)地方吃飯,那么許多頓不同的飯都會(huì)關(guān)聯(lián)到同樣的線索(就餐環(huán)境),因此就很難檢索到一周之前你享用的特定一頓飯的記憶。相反,你之前不太可能已經(jīng)把同一段旅程走了很多遍,所以回想起旅途中的細(xì)節(jié)要容易得多,因?yàn)槁贸痰谋尘皼]有關(guān)聯(lián)到任何其他記憶。
由于其他記憶痕跡關(guān)聯(lián)到同一個(gè)線索,導(dǎo)致原有的記憶被打亂,這種情況被稱作“干擾”。如果你曾學(xué)過外語,那么或許已經(jīng)遇到過這種現(xiàn)象。記憶干擾可能讓你無法想起一種語言的單詞,而另一種語言中的那個(gè)詞卻不停地蹦到你的腦海中。在這種情況下,干擾并不一定導(dǎo)致記憶丟失,但原來的記憶痕跡被阻斷了,因此暫時(shí)無法重新想起。
研究發(fā)現(xiàn),克服阻斷干擾的唯一辦法,就是有意識(shí)地努力恢復(fù)正確的記憶痕跡(而且要保持耐心,因?yàn)檫@可能會(huì)花些時(shí)間)。不過,干擾也可能導(dǎo)致永久性的記憶丟失。研究記憶的科學(xué)家將此稱為檢索引起的遺忘(RIF)。
為了說明這種現(xiàn)象,考慮下面的試驗(yàn):學(xué)生們先學(xué)習(xí)A和B兩個(gè)島的各10個(gè)地理知識(shí)。接下來,在關(guān)于島A的10個(gè)知識(shí)中,練習(xí)想起其中的5個(gè)。之后測試他們對這些知識(shí)的掌握程度。
你認(rèn)為學(xué)生對島A相關(guān)知識(shí)的記憶會(huì)是什么情況?
不出意料,檢索練習(xí)增強(qiáng)了所練習(xí)的5個(gè)知識(shí)的記憶(正確率高于島B的相關(guān)知識(shí)),但這也使學(xué)生對島A沒有得到練習(xí)的5個(gè)知識(shí)的記憶變差了。這是什么原因呢?
島A是關(guān)于島A的相關(guān)信息的背景線索,島B也是關(guān)于島B的相關(guān)信息的背景線索。在從記憶中檢索關(guān)于島A的5個(gè)知識(shí)時(shí),它們與背景線索之間的聯(lián)系被加強(qiáng)了,而剩下5個(gè)知識(shí)與背景線索之間的聯(lián)系則被削弱了(參見“測試效應(yīng)”)。
這項(xiàng)研究對于學(xué)習(xí)的一個(gè)主要啟示在于,選擇性練習(xí)測試能夠大幅提高所練習(xí)項(xiàng)目的記憶表現(xiàn),但同時(shí)也會(huì)削弱對于未練習(xí)項(xiàng)目的記憶表現(xiàn)。我們怎樣才能克服干擾導(dǎo)致的遺忘呢?
克服干擾的一個(gè)辦法是明確呈現(xiàn)出干擾。如果你經(jīng)常弄混一些概念,那么就把它們放在一起,然后同時(shí)復(fù)習(xí)它們。
總體思想是,不論學(xué)習(xí)什么,讓不同概念盡可能區(qū)分開來都是個(gè)好辦法,因?yàn)檫@會(huì)強(qiáng)迫你的大腦把它們編碼成不相似的記憶痕跡。為此,你可以強(qiáng)調(diào)學(xué)習(xí)材料中不同概念之間的差異(例如通過比較和對比)。
另一個(gè)有效的辦法是把多個(gè)概念整合起來。例如,如果你在記憶特定動(dòng)物/植物家族的成員,則試著找出這些成員之間所有可能的關(guān)聯(lián)。等你日后要檢索這些成員的記憶時(shí),它們就不再為進(jìn)入你的意識(shí)相互競爭,而是以一種整體的形式被緊密地編碼在一起。如此就不再是一個(gè)概念阻斷其他概念,而是會(huì)被一起檢索出來。
科學(xué)家發(fā)現(xiàn),學(xué)習(xí)目的也會(huì)影響我們克服干擾的效果。關(guān)注相對表現(xiàn)(相比于其他學(xué)生,他們做得怎么樣)的學(xué)生往往只用到淺層加工(不尋找概念之間的關(guān)聯(lián)),而目標(biāo)是掌握知識(shí)的學(xué)生常常會(huì)用到更多深層加工,例如在不同概念之間建立聯(lián)系。
總結(jié)起來,我們推薦以下做法:
·重復(fù)學(xué)習(xí)你感到困惑的概念
·利用比較和對比來發(fā)現(xiàn)不同概念之間的區(qū)別
·把多個(gè)概念整合起來(發(fā)現(xiàn)概念之間的聯(lián)系)
·致力于掌握知識(shí)本身,而不要關(guān)注其他人的表現(xiàn)