We are always changing. Literally. In a region of the brain called the hippocampus, about 3 percent of neurons are replaced each month. Red blood cells get a little overripe after a few months in service and are trashed in favor of new ones. Proteins have a shelf life, after which they are degraded and new copies are substituted. You'd be hard-pressed to find a single molecule in your body that was there at birth.

This unsettles me - the idea that the me sitting here is destined to be reconstituted with all new molecules. It would probably unsettle anyone. On a psychological level, we are all resistant to the inevitability of change, all biased to believe that what is, will always be. This isn't just an academic concern; it's pertinent to the new world dawning in a few weeks.

If you carry out a "longitudinal" study - follow your subjects for decades, as scientists have done - and, at various points, assess their personalities and values, you'll find that there's a steady rate of change throughout. We're all constantly evolving. Then try asking your subjects a retrospective question: How much has your personality changed in the last decade? What about your values? From teenagers to grandparents, people give relatively accurate assessments.

Now, instead, ask your subjects a prospective question: How much do you think your personality and values will change in the next decade? People systematically underestimate the extent. They believe that the person they are today is the person they will always be.

Belgian scientist Jordi Quoidbach and his colleagues first discovered this phenomenon. In a 2013 Science paper, they called it the "end-of-history illusion". People recognize the changes they've undergone but resist the idea that change will continue unabated into the future. Intellectually, history ends with the present.

This phenomenon is reflected in how we perceive our tastes and our social patterns. Who was your best friend 10 years ago? Joe Blow from Outer Mongolia, to whom you haven't spoken in years. Who do you predict will be your best friend 10 years from now? Well, of course, my current BFF. It's hard to imagine that a relationship that so matters in your present could drift into irrelevance, as so many have in the past. What was your favorite band 10 years ago? Some flash-in-the-pan group you'd be embarrassed to be caught listening to today. And a decade from now? Well, your current favorite, of course - hey, this is music for the ages.

It makes intuitive sense that, while remembering specific changes from the past, people have trouble picturing specific changes in the future. How can we contemplate liking some new singer in a decade who probably is in middle school now? But this limitation evidently extends beyond specifics; we have trouble contemplating how much we will "change as a person".

Quoidbach and his colleagues found that this end-of-history illusion produces bad economic decisions. How much would you pay to go to a concert by that band you loved a decade ago? "Them? Two cents." How much would you pay for tickets to a concert in a decade by your current favorite? "Lots, they'll be even more awesome by then." There's no better example of the economic consequences of the end-of-history illusion than people paying to remove tattoos - who would have guessed that your opinion would change about those ink portraits of Pokemon characters?

We view our present selves as having finally arrived, finally evolved into the person we were always meant to be. We can recognize that we are the end-product of all those changes over the years. But no way will this slow evolution just keep going, we think.

In various ways, then, we tend to find the present to be, well, so powerfully present, that it's hard to imagine that it will prove as fleeting as all those dimly remembered pasts. But - here's the conclusion to my long windup - we'll need to be more imaginative.

I feel as if we are in crisis like nothing in my lifetime, and I know I'm not alone.

To fight this despair, I remind myself daily of the end-of-history illusion.

I try to both think and feel the fact that the present about to cave in on us eventually will be the past. We can hasten that process if we struggle against it every inch of the way.

Tribune News Service

每一天，一個(gè)全新的你

我們始終處于變化之中，這種變化實(shí)實(shí)在在。我們大腦中有個(gè)叫海馬體的區(qū)域，每個(gè)月都有3%的神經(jīng)細(xì)胞會(huì)被替換掉。紅血細(xì)胞在為人體服務(wù)數(shù)月后會(huì)失去活力，然后會(huì)被新的紅血細(xì)胞取代。蛋白質(zhì)也有保質(zhì)期，過(guò)期后它們就會(huì)被分解，為新的所取代。你很難從身體里找到哪怕一個(gè)分子是自你出生就存在的。

這種想法讓我很不安——即現(xiàn)在坐在這里的我注定要被全新的分子重構(gòu)。這也許會(huì)讓任何人都感到不安。心理上，我們都抗拒這種變化的必然性，我們都一廂情愿地相信，現(xiàn)狀會(huì)永遠(yuǎn)繼續(xù)。這不僅僅是一個(gè)學(xué)術(shù)問(wèn)題：它也關(guān)系到未來(lái)幾周后即將出現(xiàn)的新世界。

如果你從事一項(xiàng)“縱向”研究——像科學(xué)家那樣，追蹤受試者數(shù)十年，并在不同的時(shí)點(diǎn)評(píng)估他們的性格和價(jià)值觀，你會(huì)發(fā)現(xiàn)，自始至終他們的變化速率非常穩(wěn)定。我們都在不斷進(jìn)化。然后，你問(wèn)你的受試者一個(gè)回顧性的問(wèn)題：在過(guò)去10年中，你的性格改變了多少？?jī)r(jià)值觀改變了多少？從青少年到老人，他們都會(huì)給出相對(duì)準(zhǔn)確的評(píng)估。

現(xiàn)在，你再問(wèn)你的受試者一個(gè)預(yù)測(cè)性問(wèn)題：你覺得未來(lái)10年自己的性格和價(jià)值觀會(huì)改變多少？人們通常會(huì)低估改變的程度。他們認(rèn)為當(dāng)下的自己會(huì)永遠(yuǎn)如此。

比利時(shí)科學(xué)家若爾迪·霍爾迪巴克和他的同事首先發(fā)現(xiàn)了這一現(xiàn)象。在2013年《科學(xué)》雜志上發(fā)表的一篇論文中，他們將其稱為“歷史終結(jié)錯(cuò)覺”。人們承認(rèn)過(guò)去的變化，但拒絕接受未來(lái)也會(huì)同樣變化的道理。在人們的頭腦中，歷史終結(jié)于當(dāng)下。

這種現(xiàn)象反映在我們對(duì)品味和社交模式的認(rèn)知上。誰(shuí)是10年前你最好的朋友？一個(gè)你已多年未曾聯(lián)系的來(lái)自蒙古的某個(gè)人。再預(yù)測(cè)一下，誰(shuí)會(huì)是你10年后最好的朋友？那當(dāng)然是我現(xiàn)在最好的朋友了。你很難想象現(xiàn)在對(duì)你如此重要的關(guān)系，會(huì)和過(guò)去很多關(guān)系一樣，逐漸淡化成毫不相關(guān)的事。10年前你最喜歡的樂隊(duì)是哪個(gè)？也許不過(guò)是某個(gè)曇花一現(xiàn)的組合，而現(xiàn)在你可能都羞于被別人發(fā)現(xiàn)在聽他們的音樂。那么10年后呢？當(dāng)然是你現(xiàn)在最喜歡的樂隊(duì)——嘿，他們的音樂會(huì)經(jīng)久不衰。

從直覺上說(shuō)，這不無(wú)道理。人們雖然能記得過(guò)去具體的改變，卻很難想象未來(lái)的具體變化。我們?cè)趺茨軌蝾A(yù)期自己喜歡10年后出現(xiàn)的新歌手？他沒準(zhǔn)現(xiàn)在還在讀中學(xué)呢。但這種思維局限顯然不止于具體事情；我們很難預(yù)測(cè)自己“作為一個(gè)人會(huì)有多大改變”。

霍爾迪巴克和他的同事發(fā)現(xiàn)，這種歷史終結(jié)錯(cuò)覺會(huì)讓人在經(jīng)濟(jì)方面做出糟糕的決定。要是讓你現(xiàn)在去聽自己10年前喜歡的樂隊(duì)的演唱會(huì)，你打算付多少錢？“他們嗎？2美分吧。”要是讓你10年后去聽你現(xiàn)在最喜歡的樂隊(duì)的演唱會(huì)，你愿意付多少錢？“很多。到那時(shí)他們會(huì)更棒。”人們花錢除掉紋身的例子，最能反映歷史終結(jié)錯(cuò)覺的經(jīng)濟(jì)行為后果——誰(shuí)能想到你對(duì)“口袋妖怪”紋身的想法會(huì)發(fā)生改變？

我們認(rèn)為當(dāng)下的自己已經(jīng)定型，最終演變成了我們應(yīng)該成為的自己。我們會(huì)認(rèn)為自己是過(guò)去所有變化的終極產(chǎn)物；在我們看來(lái)，這種緩慢的演變絕不會(huì)繼續(xù)發(fā)生。

在種種情形下，我們會(huì)發(fā)現(xiàn)當(dāng)下如此真切強(qiáng)大，以至于我們很難想象，它會(huì)和那些我們只有朦朧記憶的過(guò)去一樣轉(zhuǎn)瞬即逝。但——這就是我鋪陳到此的結(jié)論——我們需要更具想象力。

我感覺我們就像身處一場(chǎng)空前的危機(jī)之中，而且我知道，有如此想法者不只我一人。

為了對(duì)抗這種絕望，我每天都提醒自己歷史終結(jié)錯(cuò)覺的存在。

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上期獲獎(jiǎng)?wù)撸宏兾魑靼?第四軍醫(yī)大學(xué) 郭志華