遗忘的终结

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.

當约书亚叔叔（彼得·德弗里斯1959年的小说《邪恶的帐篷》中的人物）说，回忆“已跟过去不同了”，他说这话是想达到幽默的效果：他想告诉沉浸于过去的人，没有什么能够经受时间的考验，即便是记忆本身也不行。不过，约书亚叔叔的话已相当过时了：虽然技术在一往无前地朝着未来前进，但也不断改变着我们看待过去的方式。

怀旧通常被定义为心理上一种对往昔的渴望。这种渴望在1888年发生了重大变化。那年，柯达发布了第一部针对业余爱好者的相机，并获得了商业上的成功。很快，广告将这种相机定位成回忆孩子成长、记录家庭庆祝活动的必要工具。按照《柯达与怀旧镜头》一书的作者南希·玛莎·韦斯特的说法，这种相机“让人们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经历”。

技术时刻准备着再一次改变我们回忆过往的方式。以往，怀旧情绪几乎都是自然引发的：在收音机上听到了你毕业舞会上那首轻柔的歌，或是假期在家快速翻阅相册的时候。而今天，由于有了各种设备，我们可以随时体验怀旧。一个叫“日晷”的应用程序能重播一年前的这个时候你正在听的音乐。“濒危声音博物馆”网站则会播放已停产产品发出的各种声音（比如贝尔电话的铃声）。endprint

这仅仅是开始：这些应用程序和网站让我们可以一瞥往昔，而其他的技术能让我们更加直接地置身其中。不过，尽管心理学家们认为，怀旧对于发现人生意义、对抗孤独至关重要，但是我们还不确定过度怀旧是否会带来消极的甚至是反乌托邦式的效果。当技术为我们找回记忆提供了前所未有的便利，我们会渴望那忘东忘西的美好时光吗？

打破3D墙

苏珊·桑塔格在她1977年的散文集《论摄影》中写道，照片“积极地调动起怀旧情绪……方法是提取某一瞬间，将其定格下来”。由于照片的视角是固定的，所以观看者不能在其中移动，也无法像摄影师或是被拍摄者那样体验被拍下的空间。然而，新技术能够将照片转换成三维图形，能够产生在空间中移动的错觉。

设想一下，将“子弹时间”效果用在旧的全家福照片上，在笔记本电脑上观看效果会如何。“子弹时间”效果因《黑客帝国》而广为人知，在这部电影里，某个场景的动作会停止或急剧减速，与此同时镜头似乎以正常的速度穿梭于画面之中。《黑客帝国》需要120台相机才能营造出其招牌特效，但现在通过一种叫作三维相机绘图的技术，特效组就能为二维照片增加一重维度，且花费不贵。近来，像尼克拉·法拉瓦伊这样的媒体设计师们已经用这一方法来优化单反静物照相机拍摄的档案图片，给了观看者这样一种感觉：他们仿佛在数年前所拍摄到的地方到处走动。

艺术家还利用其他的新技术将旧照片投射在三维空间。比如，在制作《一个20世纪40年代的胡桃夹》时，俄亥俄州曼斯菲尔德的Neos舞蹈剧院就用三维图像软件，将曼斯菲尔德20世纪40年代的照片转换成虚拟背景，舞蹈演员们可以与之互动，营造出他们在旧街道上来来往往的错觉。这样一来，20世纪40年代长大的观众就能产生在童年场景中穿行的感觉。

重现历史

即使是3D电影也不能完全唤起真实的生活体验。观影者永远无法选择自己的视角，比如说自己走进另一个房间，或者是从一个孩子的位置而不是一个更高的成年人的位置来看某个场景。虚拟现实技术有望为使用者们提供这样做的机会。

虚拟现实未来如何实现个性化，有一个非常吸引人的实例。萨拉·罗斯伯格是纽约大学一名专门研究虚拟现实的研究员，她在“回忆之地：我的房子”的艺术展中重造了她的旧房子，这一展览需带上Oculus Rift虚拟现实设备来体验和游览。人一进入各式各样的房间，系统就会收到提示开始播放家庭录像，这些录像是几年前由罗斯伯格已故的父亲拍摄的。她父亲那时刚患上阿兹海默症，这也是促使她开展这个项目的原因。在对录像和照片进行了数月钻研之后，罗斯伯格产生了怀疑，认为该项目带来的体验不会把额外的记忆挖掘出来。不过，当她戴上Oculus Rift头盔，穿过虚拟房子里铺着木地板的走廊时，她感觉到了一些异样：在她家现实的房子里，有一块地板松了，一头翘了起来，但很多年来她都没有在意这件事。随着虚拟现实设备越来越便宜，我们更多人都将能在虚拟现实中重造我们小时候的家，然后在那里游览。你可以把这想象成一个沉浸式、自传版的《我的世界》和《模拟人生》。

记忆备份

当然了，一个人要想欣赏到有关自己过往的逼真复制品，就得对自己的过去有着清晰的记忆，而记忆通常会随着年龄的增长而衰退。但是，在其他灵长类动物身上的实验表明，技术的介入可能会在将来某一天帮助我们克服这一弱点。南加利福尼亚大学的生物医学工程师、神经系统科学家西奥多·伯杰开发出了一种方法，可以将大脑用来对短期记忆进行编码的神经元放电模式转化为大脑储存长期记忆的模式，他将其比作把“西班牙語翻译成法语，而且不用懂得其中任何一种语言”。一些对人的试验也表明，这种转换有90%的准确率。通过这一方法，伯杰的研究小组创建了一个数学模型，记录恒河猴的大脑在对刺激做出反应时发出的信号，对其进行转化，然后将信号反馈给大脑，以便促进长期回忆的形成。

有一天，我们也许能为我们的记忆建立备份。2011年，由认知神经科学家杰克·盖伦领导的加州大学伯克利分校的研究员们进行了一系列复杂的实验，其中包括在为受试者播放视频时对其脑部进行磁共振扫描，然后利用数学模型，测出视觉图像是怎样转化为大脑活动的。为受试者放完一段新视频后，研究人员利用生成的功能磁共振数据展开反向工程，用存档文件中其他的视频做成一个视频混剪，这个视频与受试者之前看过的视频极为相似。盖伦认为，有朝一日，我们能够绘出由回忆激发的大脑活动，然后利用反向工程，制造出关于这一回忆的视频。

尽管如此，对记忆电影来说，目前还有一段很长的路要走。在2015年的一次实验中，盖伦发现，模型在推测受试者正在看的图像时，比推测其回想的图像时准确了三倍。另一个难点是，记忆尤其是怀旧的记忆，会随着时间的推移而改变。盖伦告诉我说：“你回忆起来的其实是虚构的，即使你能对大脑中破解的记忆进行如实的重组，这一记忆本身也已经是错误的了。”

即便是我们能完全想起来，为了维持心理平衡和我们当下的生活，也要尽量避免去不停地重现记忆。同样，也不要点开一个又一个怀旧应用程序。克莱·劳特利奇是北达科他州立大学的心理学教授，所写的有关怀旧的教科书首屈一指。他认为，怀旧心理通常是健康的，适度的怀旧能够引导你去寻求新的体验。但他也警告说“用太多的时间关注过去，可能会危害你抓住机会参与其他活动的能力，而这些机会正好能构成未来怀旧记忆的基础”。也就是说，在未来，如果你记住的只有一边刷手机一边回忆的时光，怀旧也真的就与以往不同了。endprint