遺忘的終結

When Uncle Joshua， a character in Peter De Vriess 1959 novel， The Tents of Wickedness， says that nostalgia “aint what it used to be，” the line is played for humor： To those stuck in the past， nothing—not even memory itself—survives the test of time. And yet Uncle Joshuas words have themselves aged pretty well： Technology， though ceaselessly striving toward the future， has continually revised how we view the past.

Nostalgia—generally defined as a sentimental longing for bygone times—underwent a particularly significant metamorphosis1） in 1888， when Kodak released the first commercially successful camera for amateurs. Ads soon positioned it as a necessary instrument for preserving recollections of children and family celebrations. According to Nancy Martha West， the author of Kodak and the Lens of Nostalgia， the camera “allowed people … to arrange their lives in such a way that painful or unpleasant aspects were systematically erased.”

Technology is poised to once again revolutionize the way we recall the past. Not so long ago， nostalgias triggers were mostly spontaneous： catching your prom2）s slow-dance song on the radio， riffling through photo albums while you were home for the holidays. Today， thanks to our devices， we can experience nostalgia on demand. The app， Sundial， replays the songs you were listening to exactly a year ago. The Museum of Endangered Sounds website plays the noises of discontinued products （the chime of a Bell phone）.

This is just the beginning： While these apps and websites let us glimpse the past， other technologies could place us more squarely inside it. But although psychologists believe nostalgia is crucial for finding meaning in life and for combatting loneliness， we dont yet know whether too much of it will have negative， even dystopian3）， effects. As technology gives us unprecedented access to our memories， might we yearn for the good old days when we forgot things？

Breaking the 3-D Wall

In her 1977 essay collection， On Photography， Susan Sontag wrote that photos “actively promote nostalgia … by slicing out [a] moment and freezing it.” Because a photographs perspective is fixed， a viewer cant move within it， and is unable to experience the captured space the way the photographer or her subject did. New technology， however， can turn old photos into 3-D graphics4） that provide the illusion of moving through space.

Imagine the “bullet time5）” effect made famous by The Matrix—in which a scenes action is either stopped or dramatically slowed down， while a camera seems to weave through the tableau6） at normal speed—applied to an old family photo， viewed on your laptop. Whereas The Matrix required 120 cameras to achieve its signature effect， a new approach known as 3-D camera mapping allows special-effects teams to inexpensively add dimensionality to 2-D photos. Recently， media designers like Miklós Falvay have used the approach to enhance archiva7） images taken with a single still camera， giving viewers the impression that they are navigating spaces photographed years ago.endprint

Artists have used other new techniques to project old photographs onto 3-D spaces. For its production of A 1940s Nutcracker， for example， the Neos Dance Theatre， in Mansfield， Ohio， used 3-D-graphics software to transform 1940s photos of Mansfield into virtual set pieces that dancers could interact with， creating the illusion that they were moving through old city streets. In this way， audience members who grew up in the 40s were treated to the feeling of traveling through childhood landscapes.

Reliving History

Even in 3-D， movies have a limited capacity for evoking real-life experiences. A viewer will never be able to choose his own perspective—to walk to another room， say， or to view a scene from the vantage8） point of a child rather than from that of a taller adult. Virtual-reality technology promises to give users a chance to do just that.

In a tantalizing example of how VR might be personalized in the future， Sarah Rothberg， an NYU researcher who specializes in virtual reality， has re-created her old house in “Memory Place： My House，” an Oculus Rift9） experience cum10） traveling art exhibit. Entering various rooms prompts the playing of home videos， filmed years before by Rothbergs late father， whose early-onset Alzheimers disease inspired the project. After months of poring over old footage and photos， Rothberg was skeptical that the resulting experience would dislodge additional memories， but when she put on the Oculus Rift headset and walked across the virtual houses parquet11）-floored hallway， something felt off： In the real house， a floorboard had been loose and rose at one end， though she had not thought about that fact in many years. As VR gear becomes cheaper， more of us might be able to re-create and then tour our own childhood homes—imagine an immersive， autobiographical version of Minecraft12） or The Sims13）.

Backing up Your Memories

Of course， to appreciate detailed replications of ones past， one must have detailed memories of ones past—and memory typically deteriorates with age. But experiments on other primates14） suggest that technological interventions may one day help us overcome this frailty. Theodore Berger， a biomedical engineer and neuroscientist at the University of Southern California， has developed a means of translating the neuron-firing pattern that the brain uses to code short-term memory into the pattern it uses to store long-term memory—a method he likens to translating “Spanish to French without being able to understand either language.” In some human trials， the translations have been found to be 90 percent accurate. Using this method， Bergers team has created a mathematical model capable of recording the signals a rhesus15） monkeys brain produces in response to stimuli， translating them， and feeding them back to the brain in order to facilitate long-term recall.endprint

One day， we may even be able to create backups of our memories. In 2011， UC Berkeley researchers led by Jack Gallant， a cognitive neuroscientist， conducted an elaborate series of experiments that involved showing subjects video clips while taking fMRI16） scans of their brains， and then using a mathematical model to map how visual patterns translated into brain activity. After presenting a new clip to the subjects， the researchers used the resulting fMRI data to reverse engineer， from an archive of other footage， a video mashup that bore a striking resemblance to the clip the subjects had actually seen. Gallant believes that we could one day map brain activity triggered by a recalled memory and then reverse engineer a video of that memory.

For now， though， memory movies are a long way off. In a 2015 experiment， Gallant found that his model was three times more accurate at guessing the image a subject was looking at than at guessing one she was merely recalling. Another difficulty is that memories， especially nostalgic ones， shift over time. “What you recall is confabulated17）， made up，” Gallant told me. “Even if you can make a faithful reconstruction of a memory you decode from the brain， that memory is already wrong.”

Even if we had total recall， it might be best to avoid incessantly replaying memories， both for the sake of our psychological equilibrium18） and for the sake of our lives in the here and now. Ditto clicking from one nostalgia app to another. Clay Routledge， a psychology professor at North Dakota State University who wrote the leading textbook on nostalgia， says the emotion is typically healthy； in moderation， it can even lead you to seek out new experiences. But he cautions that “too much time focusing on the past could jeopardize19） your ability to engage in other opportunities that will form the basis for future nostalgic memories.” In other words， nostalgia really wont be what it once was if， in the future， you have nothing to remember but the time you spent swiping through your phone， remembering.

當約書亞叔叔（彼得·德弗里斯1959年的小說《邪惡的帳篷》中的人物）說，回憶“已跟過去不同了”，他說這話是想達到幽默的效果：他想告訴沉浸于過去的人，沒有什么能夠經受時間的考驗，即便是記憶本身也不行。不過，約書亞叔叔的話已相當過時了：雖然技術在一往無前地朝著未來前進，但也不斷改變著我們看待過去的方式。

懷舊通常被定義為心理上一種對往昔的渴望。這種渴望在1888年發生了重大變化。那年，柯達發布了第一部針對業余愛好者的相機，并獲得了商業上的成功。很快，廣告將這種相機定位成回憶孩子成長、記錄家庭慶?；顒拥谋匾ぞ?。按照《柯達與懷舊鏡頭》一書的作者南?！が斏ろf斯特的說法，這種相機“讓人們以新的方式安排自己的生活，有意地抹去了痛苦的或不愉快的經歷”。

技術時刻準備著再一次改變我們回憶過往的方式。以往，懷舊情緒幾乎都是自然引發的：在收音機上聽到了你畢業舞會上那首輕柔的歌，或是假期在家快速翻閱相冊的時候。而今天，由于有了各種設備，我們可以隨時體驗懷舊。一個叫“日晷”的應用程序能重播一年前的這個時候你正在聽的音樂?！盀l危聲音博物館”網站則會播放已停產產品發出的各種聲音（比如貝爾電話的鈴聲）。endprint

這僅僅是開始：這些應用程序和網站讓我們可以一瞥往昔，而其他的技術能讓我們更加直接地置身其中。不過，盡管心理學家們認為，懷舊對于發現人生意義、對抗孤獨至關重要，但是我們還不確定過度懷舊是否會帶來消極的甚至是反烏托邦式的效果。當技術為我們找回記憶提供了前所未有的便利，我們會渴望那忘東忘西的美好時光嗎？

打破3D墻

蘇珊·桑塔格在她1977年的散文集《論攝影》中寫道，照片“積極地調動起懷舊情緒……方法是提取某一瞬間，將其定格下來”。由于照片的視角是固定的，所以觀看者不能在其中移動，也無法像攝影師或是被拍攝者那樣體驗被拍下的空間。然而，新技術能夠將照片轉換成三維圖形，能夠產生在空間中移動的錯覺。

設想一下，將“子彈時間”效果用在舊的全家福照片上，在筆記本電腦上觀看效果會如何?！白訌棔r間”效果因《黑客帝國》而廣為人知，在這部電影里，某個場景的動作會停止或急劇減速，與此同時鏡頭似乎以正常的速度穿梭于畫面之中?！逗诳偷蹏沸枰?20臺相機才能營造出其招牌特效，但現在通過一種叫作三維相機繪圖的技術，特效組就能為二維照片增加一重維度，且花費不貴。近來，像尼克拉·法拉瓦伊這樣的媒體設計師們已經用這一方法來優化單反靜物照相機拍攝的檔案圖片，給了觀看者這樣一種感覺：他們仿佛在數年前所拍攝到的地方到處走動。

藝術家還利用其他的新技術將舊照片投射在三維空間。比如，在制作《一個20世紀40年代的胡桃夾》時，俄亥俄州曼斯菲爾德的Neos舞蹈劇院就用三維圖像軟件，將曼斯菲爾德20世紀40年代的照片轉換成虛擬背景，舞蹈演員們可以與之互動，營造出他們在舊街道上來來往往的錯覺。這樣一來，20世紀40年代長大的觀眾就能產生在童年場景中穿行的感覺。

重現歷史

即使是3D電影也不能完全喚起真實的生活體驗。觀影者永遠無法選擇自己的視角，比如說自己走進另一個房間，或者是從一個孩子的位置而不是一個更高的成年人的位置來看某個場景。虛擬現實技術有望為使用者們提供這樣做的機會。

虛擬現實未來如何實現個性化，有一個非常吸引人的實例。薩拉·羅斯伯格是紐約大學一名專門研究虛擬現實的研究員，她在“回憶之地：我的房子”的藝術展中重造了她的舊房子，這一展覽需帶上Oculus Rift虛擬現實設備來體驗和游覽。人一進入各式各樣的房間，系統就會收到提示開始播放家庭錄像，這些錄像是幾年前由羅斯伯格已故的父親拍攝的。她父親那時剛患上阿茲海默癥，這也是促使她開展這個項目的原因。在對錄像和照片進行了數月鉆研之后，羅斯伯格產生了懷疑，認為該項目帶來的體驗不會把額外的記憶挖掘出來。不過，當她戴上Oculus Rift頭盔，穿過虛擬房子里鋪著木地板的走廊時，她感覺到了一些異樣：在她家現實的房子里，有一塊地板松了，一頭翹了起來，但很多年來她都沒有在意這件事。隨著虛擬現實設備越來越便宜，我們更多人都將能在虛擬現實中重造我們小時候的家，然后在那里游覽。你可以把這想象成一個沉浸式、自傳版的《我的世界》和《模擬人生》。

記憶備份

當然了，一個人要想欣賞到有關自己過往的逼真復制品，就得對自己的過去有著清晰的記憶，而記憶通常會隨著年齡的增長而衰退。但是，在其他靈長類動物身上的實驗表明，技術的介入可能會在將來某一天幫助我們克服這一弱點。南加利福尼亞大學的生物醫學工程師、神經系統科學家西奧多·伯杰開發出了一種方法，可以將大腦用來對短期記憶進行編碼的神經元放電模式轉化為大腦儲存長期記憶的模式，他將其比作把“西班牙語翻譯成法語，而且不用懂得其中任何一種語言”。一些對人的試驗也表明，這種轉換有90%的準確率。通過這一方法，伯杰的研究小組創建了一個數學模型，記錄恒河猴的大腦在對刺激做出反應時發出的信號，對其進行轉化，然后將信號反饋給大腦，以便促進長期回憶的形成。

有一天，我們也許能為我們的記憶建立備份。2011年，由認知神經科學家杰克·蓋倫領導的加州大學伯克利分校的研究員們進行了一系列復雜的實驗，其中包括在為受試者播放視頻時對其腦部進行磁共振掃描，然后利用數學模型，測出視覺圖像是怎樣轉化為大腦活動的。為受試者放完一段新視頻后，研究人員利用生成的功能磁共振數據展開反向工程，用存檔文件中其他的視頻做成一個視頻混剪，這個視頻與受試者之前看過的視頻極為相似。蓋倫認為，有朝一日，我們能夠繪出由回憶激發的大腦活動，然后利用反向工程，制造出關于這一回憶的視頻。

盡管如此，對記憶電影來說，目前還有一段很長的路要走。在2015年的一次實驗中，蓋倫發現，模型在推測受試者正在看的圖像時，比推測其回想的圖像時準確了三倍。另一個難點是，記憶尤其是懷舊的記憶，會隨著時間的推移而改變。蓋倫告訴我說：“你回憶起來的其實是虛構的，即使你能對大腦中破解的記憶進行如實的重組，這一記憶本身也已經是錯誤的了?！?/p>

即便是我們能完全想起來，為了維持心理平衡和我們當下的生活，也要盡量避免去不停地重現記憶。同樣，也不要點開一個又一個懷舊應用程序?？巳R·勞特利奇是北達科他州立大學的心理學教授，所寫的有關懷舊的教科書首屈一指。他認為，懷舊心理通常是健康的，適度的懷舊能夠引導你去尋求新的體驗。但他也警告說“用太多的時間關注過去，可能會危害你抓住機會參與其他活動的能力，而這些機會正好能構成未來懷舊記憶的基礎”。也就是說，在未來，如果你記住的只有一邊刷手機一邊回憶的時光，懷舊也真的就與以往不同了。endprint