被遺忘的童年——為什么以前的記憶會逐漸消失？

Mellissa Block （Host）： Memories are a big part of our identities. Recalling our experiences helps us know who we are. Yet there are some events we can’t recall even though they may have helped shape our lives. These are things that occurred in the first three or four years of life.

Jon Hamilton： Francis Csedrik just turned eight and lives in Washington D.C. Like most kids， he remembers lots of important events in his life so far. There was the time he got a 1）concussion.

Francis Csedrik： I fell， head first， on a marble floor.

Hamilton： The day he watched the family car get stolen.

Francis： And my dad had to chase it down the block.

Hamilton： Then there was the morning he encountered an unexpected visitor.

Francis： A black bat sleeping right above our door.

Joanne Csedrik： The bat， oh， you remember that.

Hamilton： That’s Francis’s mom， Joanne Csedrik. She’s been asking her son about things that happened to him when he was four， or almost four. Then she asks him about an earlier event that took place when he was just three， a family trip to the Philippines.

Joanne： It was to celebrate someone’s birthday.

Francis： Mm-mm.

Joanne： You don’t remember？ We took a long plane ride， two boat trips.

Francis： No， I don’t remember.

Hamilton： That’s not surprising. Patricia Bauer of Emory University says by the time most kids are seven or eight， they have started losing some of their early memories. And she says experiences will continue to disappear over the next few years.

Patricia Bauer： Most adults do not have memories of their lives for the first three to three and a half years.

Hamilton： Bauer says scientists once thought childhood amnesia occurred because the brains of young children simply couldn’t form lasting memories of events. Then in the 1980s， she and other researchers began testing the memories of children as young as nine months old， using gestures and objects instead of words.

Bauer： And what we found was that even as young as the second year of life， children had very 2）robust memories for these specific past events.

Hamilton： And that raised a question： If children can remember what happened in their early years...

Bauer： Why is it that as adults we have difficulty remembering that period of our lives？

Hamilton： Bauer says the evidence suggests that children are somehow losing access to their early memories. She wanted to know when this was happening. So she studied a group of children to see what happened to their memories over time. At age three， she says， the kids were recorded speaking with a parent about recent events.

Bauer： They tended to be just everyday family activities， visiting an amusement park， a picnic， a visit from a relative.

Hamilton： Then as the kids got older， Bauer and her colleagues checked to see how much they remembered. She says children as old as seven could still recall most of the events.

Bauer： In contrast， the children who were eight and nine years of age， those children recalled fewer than 40% of the events. And so what we observed was actually the 3）onset of childhood 4）amnesia.

Hamilton： Francis Csedrik， who just turned eight， is right at the age when many childhood memories are fading.

Joanne： Do you remember celebrating your grandfather’s birthday in the Philippines？

Francis： Lolo Santo？

Joanne： No， not his birthday.

Hamilton： Joanne Csedrik says her son has clear memories of two more recent trips to the Philippines. But the one when he was three is gone. It’s not entirely clear why early memories are so 5）fragile. Bauer says it probably has to do with the structures and 6）circuits in the brain that store events for future recall.

Bauer： The brain systems that are responsible for forming memories at the age of three， three and a half， are still relatively immature. It doesn’t mean they’re not working at all， they certainly are. But they’re not working as efficiently and therefore not as effectively as they’re going to be working in later childhood and certainly in adulthood.

Hamilton： By the time children are seven or so， their brains are forming memories that are as robust as those formed by adults. Of course， some types of early memories are more likely than others to survive childhood amnesia. Carole Peterson， at Memorial University in Newfoundland， Canada， says one example is memories that carry a lot of emotion. She showed this in a study of children who’d been to a hospital emergency room when they were as young as two.

Carole Peterson： They had broken bones. They were 7）lacerated， had to be 8）stitched up. Things like that. So these were very emotional， very significant events. And what we have found is that even 10 years later， children have enormously good memory of them.

Hamilton： Francis Csedrik certainly remembers the events that led to his emergency room visit.

Francis： My friend Asher， he said： I want to carry you down the stairs. I didn’t want him to but he didn’t listen. He did it. And I fell， head first， on a marble floor.

Joanne： And what did they tell you at the hospital？ What did they call it？

Francis： A concussion.

Hamilton： That memory is from when Francis was four. But Peterson says a child in one of her studies remembered an event from when he was just 18 months old. It was the day his mother went to the hospital to give birth to a sibling.

Peterson： He remembers crying on the floor of the kitchen and he remembers how upset he was. And he can remember the pattern of his 9）teardrops on the 10）linoleum.

Hamilton： Findings like that are persuading 11）courts to allow more 12）eyewitness 13）testimony from children. Peterson says even very young children can be good witnesses if they are questioned in a 14）neutral way. She says another powerful 15）determinant of whether an early memory sticks is whether a child fashions it into a good story， with a time and place and a 16）coherent 17）sequence of events.

Peterson： Those are the kinds of memories that are going to last. Whereas memories like there was a flower growing up through a crack in the sidewalk， those are the ones that are more likely to be forgotten.

Hamilton： Because they aren’t part of a 18）narrative and have no context. And Peterson says that’s where parents can play a big role in what a child remembers. She says with some help， kids learn how to give shape and structure to their memories of an event.

Peterson： Follow the child’s lead. You add some more information and then encourage them to add more. So 19）essentially what you’re trying to do is co-construct a story. Hamilton： A story that won’t fade away. That’s something Joanne Csedrik and her son Francis have been doing ever since his concussion. He’s even written about the events of that day.

Francis： I just like writing that story because I just don’t want to forget it.

Joanne： Yeah， because it reminds you to be careful， right？

You don’t want to have that happen again.

Francis： Mm-mm. I think that’s a day I’ll always remember.

Hamilton： It’s not hard to see an 20）evolutionary reason for this. Kids who recall stories about danger or injuries are probably more likely to survive to become adults. Peterson says remembered stories become important for a different reason in adolescence. She says that’s when young people begin to create a larger 21）autobiography from their early narratives.

Peterson： When you start knitting them all together into a life story， you kind of put together a whole bunch of stories in order to explain why you are the kind of person you are.

Hamilton： Researchers say a person’s life story usually includes at least some events that had been lost to childhood amnesia. That’s because when our own memories fail， we rely on family members， photo albums， and videos to fill in the blanks.

梅麗莎·布洛克（主持人）：回憶是我們身份的一個重要組成部分。回想我們過去的經歷能夠幫助我們了解自己。然而，雖然有一些經歷能夠幫助我們塑造人生，可是我們卻無法想起來。這些事都發生在我們人生的頭三、四年里。

喬恩·漢密爾頓：弗朗西斯·色克德里克今年八歲了，住在華盛頓。跟大部分的孩子一樣，目前為止他能記得人生中許多重要的事件。他記得有一次得了腦震蕩。

弗朗西斯·色克德里克：我摔倒了，頭先著地，撞在了大理石地板上。

漢密爾頓：那天他記得家里的車被偷了。

弗朗西斯：然后我的爸爸得追著它滿大街地跑。

漢密爾頓：然后就是一天早上他遇到了一個不速之客。

弗朗西斯：一只黑色的蝙蝠睡在了我們的門上。

喬安妮·色克德里克：那只蝙蝠，噢，你還記得。

漢密爾頓：這是弗朗西斯的媽媽，喬安妮·色克德里克。在他四歲或者快到四歲的時候，媽媽就一直問他身邊發生的事情。然后，喬安妮問了他一件早在三歲時發生的事情，那是一次去菲律賓的家庭旅行。

喬安妮：是去慶祝某人的生日。

弗朗西斯：嗯嗯。

喬安妮：你不記得了？我們坐了很長時間的飛機，兩次輪船。

弗朗西斯：不，我不記得了。

漢密爾頓：這并不奇怪。艾莫利大學的帕特里夏·鮑爾說，大部分孩子在七、八歲的時候，就會丟失一部分早期的記憶。她還說過去的經歷會在接下來的幾年中繼續消失。

帕特里夏·鮑爾：大多數的成人都丟失了自己三到三歲半的記憶。

漢密爾頓：鮑爾說科學家們曾經認為童年經驗失憶癥的發生是因為年幼孩子們的大腦不能形成長時間的記憶。在20世紀80年代，她和其他的研究人員開始測試九個月大孩子的記憶力，使用的方法是通過手勢和物體，而不是語言。

鮑爾：我們發現，即使只有兩歲，孩子們對這些過去發生的特定事件都有很好的記憶。

漢密爾頓：這就引發一個問題：如果孩子們能記得小時候發生的事……

鮑爾：那么為什么我們成人記憶生活的點滴就那么困難？

漢密爾頓：鮑爾說證據表明不知道什么原因，孩子們會丟失早期的記憶，她希望知道這具體發生在什么階段。所以她研究了一組孩子，看看隨著時間的流逝，他們的記憶發生了怎么樣的變化。在三歲的時候，孩子們與父母談論最近發生的事情會被記錄下來。

鮑爾：它們會是家庭日常的活動，像是逛游樂園、野餐、親戚到訪。

漢密爾頓：然后隨著孩子們慢慢長大，鮑爾和同事們就會檢查他們能記得多少（以前的事）。她說七歲的孩子能夠回憶起大部分的事件。

鮑爾：相反地，八、九歲的孩子只能回憶起不到40%的事件。因此我們觀察到的就是童年經驗失憶癥的開始。

漢密爾頓：弗朗西斯·色克德里克今年剛滿8歲，正好是在很多童年回憶逐漸消退的年齡。

喬安妮：你還記得在菲律賓幫你爺爺慶祝生日嗎？

弗朗西斯：在羅羅語圣嗎？

喬安妮：不，那次不是爺爺的生日。

漢密爾頓：喬安妮說她的兒子對最近兩次去菲律賓旅行的印象深刻。但是在他三歲時的那次旅行（的記憶）卻不見了。為什么早期記憶那么脆弱的原因還不清楚。鮑爾說這可能與大腦中為將來提取記憶儲存事件的結構和回路有關。鮑爾：負責形成記憶的大腦系統在三到三歲半時還相對不成熟。但這并不代表它們不工作了，它們當然還在工作。但是它們還沒有那么高效地運作，不像在后期的童年和成人階段那么高效。

漢密爾頓：在孩子七歲左右時，他們的大腦就能形成和成人一樣清晰的記憶。當然，一些早期的記憶可能比其他的記憶更能不受童年經驗失憶癥的影響。加拿大紐芬蘭紀念大學的卡羅爾·彼得森說其中一個例子就是能夠承載很多情感的記憶。她在一份研究去過醫院急診室的兩歲兒童報告中表明了這點。

卡羅爾·彼得森：他們的骨頭斷了，受傷了，需要縫針。像是這樣的事情。這些都是情緒有很大波動、非常重大的事件。我們發現的是，盡管過去了10年，孩子們對這些事的記憶還很深刻。

漢密爾頓：弗朗西斯·色克德里克肯定記得讓他去急診室那件事。

弗朗西斯：我的朋友亞瑟，他說：“我想把你背下樓。”我不想他這樣，但是他不聽。他真的背我下去了，我摔倒了，頭朝下，撞到了大理石地板上。

喬安妮：他們在醫院告訴你什么了？他們管那叫什么？

弗朗西斯：腦震蕩。

漢密爾頓：這是弗朗西斯四歲時的記憶。但是彼得森說在她其中一個研究中，一個僅十八個月大的孩子能夠記住一件事——那天他媽媽去醫院給他生了一個弟弟或妹妹。

彼得森：他記得在廚房的地板上哭，記得自己當時有多沮喪。他還記得眼淚落在油布上的痕跡。

漢密爾頓：像這樣的發現促使法院準許更多兒童證人來提供證詞。彼得森說，如果用中立的方式進行提問，即使是很小的孩子也能成為一個好的證人。另一個證明（兒童）早期記憶存在的有利決定因素是看孩子能否將其組織成一個完整的故事，有時間、地點和一系列連貫的事件。

彼得森：這些記憶能夠持續保留下來。但是像一朵花從路邊的狹縫中長出來這樣的記憶，就很有可能被忘記。

漢密爾頓：因為這些不是敘述性（事件）的一部分，沒有任何的情境。彼得森說這就是家長在孩子們的記憶中占有重要角色的地方。她說，在一定的幫助下，孩子們能夠學會如何為一件事的記憶形成框架組織。

彼得森：讓孩子們做主導。你增加更多的信息，然后鼓勵他們也增加一些。那么，實際上你做的就是（和孩子們一起）完成一個故事的構建。

漢密爾頓：這樣的故事不會逐漸消失。這是喬安妮·色克德里克和她的兒子弗朗西斯自他得了腦震蕩后一直在做的事。他甚至把那天發生的事寫了下來。弗朗西斯：我想把那個故事寫下來，因為我不想忘記它。

喬安妮：嗯，因為那件事會提醒你以后小心點，對嗎？你不想再發生那樣的事。

弗朗西斯：嗯嗯，我想我會永遠記住那天。

漢密爾頓：不難發現，這是進化的需要。能夠記起危險和受傷經歷的孩子更有可能順利長大。彼得森說，在青春期，因為不同的原因，記住這些經歷顯得很重要。她說這就是年輕人開始用早期的敘述性事件來創造一個更大的自傳體的時期。

彼得森：當你開始把他們全部編織成一個人生故事，也就是把一大堆的故事放在一起，來解釋你為什么成為現在的自己。

漢密爾頓：彼得森說一個人的人生故事通常包括因為兒童經驗失憶癥而丟失的一些事件。那是因為當我們的記憶缺失時，我們就會依賴家庭成員、相冊、視頻去填補這些空白。

Comments：

Gunther： At 90， I live with my memories which do extend to my earliest years. I can recall the people， the dog， layout and furniture in the apartment where I lived until age 4， even without any photos. That and my hobby of genealogy cause me to write my memoirs and document my four grandparents and family genealogy.

Maria： I was 2 when Turkey invaded Cyprus （1974） and I remember the war quite clearly， as well as episodes after the war itself ended. The same goes for other people my age. So I think it’s true that memories carrying strong emotions survive.

Kelly： For pretty much my whole life， I had a recurring nightmare of a face appearing in my window. Sometimes I had to protect my younger brother from it. In my 30’s， I told my mother about this dream （I was pregnant， and it was happening a lot）. My mother explained that it wasn’t a dream： when I was a newborn， her doctor had said that she should let me “cry it out” at night. She didn’t like that， and would run around the outside of the house to look in on me. Clearly， this very early memory worked its way into my subconscious. I have not had that nightmare once since then.

Charlie： I remember when I was four， my mother made hotdogs by boiling them in a pan. I wanted another and she was busy， so I went over to the stove and reached up to grab the handle， but only managed to pull it over onto me and got second degree burns over my face and chest. I can still remember seeing the water pouring through the air at me and then I remember nothing. I’ve been told the brain removes some memories of trauma to protect itself and I can believe it.

小鏈接童年經驗失憶癥

從年齡與學習效率和記憶保存兩者關系看，多年來心理學家們即注意到了一個奇怪或矛盾的現象。三歲以前的幼兒，對事物最感好奇，事事好問，求知，是一生中學習效率最高與學習事物最多的一段時期。然而，到了成年之后，很少有人能清楚記得三歲以前的事。因此，在心理學上，就出現了所謂“幼年經驗失憶癥”這個名詞。幼年經驗失憶癥，也稱童年經驗失憶癥。幼年經驗失憶，是不是事實？如果是事實，應如何解釋？即使幼年經驗失憶是事實，應否視之失憶癥？

最早使用幼年經驗失憶癥這個名詞者，是精神分析論創始人弗洛伊德。弗洛伊德發現，當病人回憶生活經驗時，都無法說出三歲（甚至五歲）以前的舊事。按弗洛伊德的解釋，這段時間正是戀親情結形成的階段，兒童因心理沖突而生的壓抑，結果導致了對記憶的壓抑。此一解釋相當勉強，戀親情結所引起的壓抑，只限于“性沖動”一方面，有關性沖動之外經驗的失憶，又如何解釋？除了精神分析論的解釋之外，一般常識的看法是，時間太久沖淡了記憶。此種說法也不合理，原因是，18歲的人不能記得3歲以前的事，如果說是因為隔了15年，何以在過30年之后，48歲時反而能清楚記得18歲的事？

新近的研究，確定了人類3歲以前的經驗成年后不能記憶的事實。即使有些人聲稱他能記憶，那也是3歲以后別人告訴他的。該研究以大學生中有弟妹者為對象，以一份包括20個題目的問卷為工具，問卷內的題目全是關于他們弟弟或妹妹出生前后的事。諸如：你弟弟（妹妹）出生前，你母親何時去的醫院？你是否到醫院看過你的母親？你親生弟弟（妹妹）是何時到家的？經調查他們的弟妹出生時間，是在這群大學生們的1～17歲之間。結果發現：大學生中，其弟妹出生時間在他們3歲以下者，20題中沒有一題是答對的。這表示，人在3歲以前留不下長期記憶。過了3歲，分數就直線上升，在9歲左右弟妹出生者，平均答對15個題目。按現代認知心理學中信息處理理論的解釋，人在3歲以前并非沒有長期記憶。只是因為幼兒在當時對信息處理時，尚不能使用語音作為心理表征的工具，即未將語音的聲碼、形碼、意碼輸入到長期記憶之內，長期記憶中自然就貯存不下語音信息，因而不能用語音去檢索記憶以回答問題。此種解釋已為一般人所接受。