大腦的五大謎思

千百年來(lái)，大腦一直都是科學(xué)探索的神秘對(duì)象。隨著研究的深入，一些言之鑿鑿的結(jié)論公布開(kāi)來(lái)，再加上想象力的渲染等因素，人們心中對(duì)大腦有了一些普遍的認(rèn)識(shí)。只是，這些認(rèn)識(shí)是否正確？

We use only 10 percent of our brains.

我們只用到大腦的10％。

This one sounds so compelling1)—a precise number， repeated in pop culture for a century， implying that we have huge reserves of untapped2) mental powers. But the supposedly unused 90 percent of the brain is not some vestigial3) appendix4). Brains are expensive—it takes a lot of energy to build brains during fetal5) and childhood development and maintain them in adults. Evolutionarily， it would make no sense to carry around surplus6) brain tissue. Experiments using scans show that much of the brain is engaged even during simple tasks， and injury to even a small bit of brain can have profound consequences for language， sensory perception， movement or emotion.

True， we have some brain reserves. Autopsy7) studies show that many people have physical signs of Alzheimer's disease in their brains even though they were not impaired8). Apparently we can lose some brain tissue and still function pretty well. And people score higher on IQ tests if they're highly motivated， suggesting that we don't always exercise our minds at 100 percent capacity.

這一說(shuō)法聽(tīng)起來(lái)很有說(shuō)服力，不僅數(shù)據(jù)精確，而且百年來(lái)在流行文化中被反復(fù)提及，暗示我們還有巨大的腦力資源尚未開(kāi)發(fā)。然而，所謂大腦中沒(méi)用到的那90%并不是什么殘余的累贅。大腦“造價(jià)不菲”，在胎兒和童年階段，大腦的發(fā)育要消耗大量的能量，成年后又要消耗大量能量來(lái)保證它的正常運(yùn)轉(zhuǎn)。從進(jìn)化的角度講，人體內(nèi)沒(méi)道理會(huì)留下多余的大腦組織。很多實(shí)驗(yàn)通過(guò)掃描大腦發(fā)現(xiàn)，即便是執(zhí)行簡(jiǎn)單的任務(wù)也需要大腦的大部分部位參與，因而即便是大腦的一小點(diǎn)兒地方受到損傷都可能對(duì)人的語(yǔ)言、感官知覺(jué)、運(yùn)動(dòng)或情緒產(chǎn)生深遠(yuǎn)的影響。

沒(méi)錯(cuò)，我們是有一部分大腦沒(méi)用到。解剖研究發(fā)現(xiàn)，很多人大腦中都有老年癡呆癥的體征，雖然他們并沒(méi)有患病。顯然，失去某些腦組織后，我們的機(jī)體仍然能正常運(yùn)轉(zhuǎn)。而且，如果人們有足夠的動(dòng)力，就能在智力測(cè)試中取得更高的分?jǐn)?shù)，這一現(xiàn)象表明我們并不總是動(dòng)用全部大腦做事。

Flashbulb memories9) are precise， detailed and persistent.

閃光燈記憶鮮明、準(zhǔn)確而又持久。

We all have memories that feel as vivid and accurate as a snapshot， usually of some shocking， dramatic event. People remember exactly where they were， what they were doing， who they were with， what they saw or heard. But several clever experiments have tested people's memory immediately after a tragedy and again several months or years later. The test subjects tend to be confident that their memories are accurate and say the flashbulb memories are more vivid than other memories. Vivid they may be， but the memories decay over time just as other memories do. People forget important details and add incorrect ones， with no awareness that they're recreating a muddled10) scene in their minds rather than calling up a perfect， photographic reproduction.

我們腦海里都會(huì)有一些如照片般鮮活準(zhǔn)確的記憶，其內(nèi)容往往是一些令人震驚的、緊張刺激的重大事件。人們能夠清楚地記起事件發(fā)生時(shí)他們?cè)谀睦铮谧鍪裁矗l(shuí)在一起，看到或聽(tīng)到了什么。不過(guò)，研究人員已經(jīng)做了幾個(gè)精心設(shè)計(jì)的實(shí)驗(yàn)，他們?cè)谌藗冊(cè)庥霾恍沂录罅⒓礈y(cè)試人們的記憶，并在數(shù)月或數(shù)年后又測(cè)了一次。結(jié)果發(fā)現(xiàn)，受測(cè)群體往往滿懷信心地認(rèn)為他們的記憶準(zhǔn)確無(wú)誤，并表示閃光燈記憶比其他記憶更加鮮明。或許閃光燈記憶的確鮮明，但隨著時(shí)間的推移，它們也會(huì)像其他記憶一樣不斷淡化。人們會(huì)忘掉重要細(xì)節(jié)，添加錯(cuò)誤元素，絲毫意識(shí)不到自己不是在像照相般完整無(wú)缺地再現(xiàn)回憶，而是在腦海中重建一個(gè)被搞得亂糟糟的場(chǎng)景。

It's all downhill after 40 (or 50 or 60 or 70).

40 (或50、60、70)歲后大腦開(kāi)始走下坡路。

It's true， some cognitive11) skills do decline as you get older. Children are better at learning new languages than adults—and never play a game of concentration against a 10-year-old unless you're prepared to be humiliated. Young adults are faster than older adults to judge whether two objects are the same or different; they can more easily memorize a list of random words， and they are faster to count backward by sevens.

But plenty of mental skills improve with age. Vocabulary， for instance—older people know more words and understand subtle linguistic distinctions. Given a biographical sketch of a stranger， they're better judges of character. They score higher on tests of social wisdom， such as how to settle a conflict. And people get better and better over time at regulating their own emotions and finding meaning in their lives.

沒(méi)錯(cuò)，隨著年齡的增長(zhǎng)，人們的一些認(rèn)知能力的確會(huì)衰退。兒童就比成人更善于學(xué)習(xí)新的語(yǔ)言——千萬(wàn)別和一個(gè)10歲的小孩比注意力，除非你作好了丟臉的準(zhǔn)備。年輕人能比老年人更快地判斷出兩個(gè)物體是否相同，可以更輕易地記住一連串隨機(jī)的單詞，還能更快地以7為公差來(lái)倒數(shù)數(shù)字。

不過(guò)，也有很多智力技能會(huì)隨著年齡的增長(zhǎng)而提高。以詞匯量為例，年長(zhǎng)者掌握的詞匯更多，而且能夠洞悉詞語(yǔ)之間的細(xì)微差別。給出一個(gè)陌生人的生平梗概，年長(zhǎng)者能更準(zhǔn)確地判斷出這個(gè)人的性格特點(diǎn)。他們?cè)谏鐣?huì)經(jīng)驗(yàn)上更勝一籌，比如如何處理爭(zhēng)端。而且，隨著時(shí)間的推移，人們也能夠更好地調(diào)節(jié)自己的情緒，找到生命的意義。

A conk12) on the head can cause amnesia13).

頭部受擊會(huì)導(dǎo)致失憶。

Next to babies switched at birth， this is a favorite trope14) of soap operas: Someone is in a tragic accident and wakes up in the hospital unable to recognize loved ones or remember his or her own name or history.

In the real world， there are two main forms of amnesia: anterograde (the inability to form new memories) and retrograde (the inability to recall past events). Science's most famous amnesia patient， H.M.， was unable to remember anything that happened after a 1953 surgery that removed most of his hippocampus15). He remembered earlier events， however， and was able to learn new skills and vocabulary， showing that encoding \"episodic\" memories16) of new experiences relies on different brain regions than other types of learning and memory do. Retrograde amnesia can be caused by Alzheimer's disease， traumatic17) brain injury， thiamine18) deficiency or other insults. But a brain injury doesn't selectively impair autobiographical memory—much less bring it back.

除了嬰兒出生時(shí)被調(diào)包，肥皂劇中最常見(jiàn)的狗血?jiǎng)∏榫湍^(guò)于失憶了：某人慘遭事故，在醫(yī)院醒來(lái)后不認(rèn)識(shí)自己的親人或是記不起自己的名字或過(guò)去的經(jīng)歷。

在現(xiàn)實(shí)生活中，失憶主要有兩種：順行性失憶(無(wú)法形成新的記憶)和逆行性失憶(無(wú)法憶起過(guò)去的事情)。科學(xué)史上最著名的失憶癥患者亨利·莫萊森在1953年的手術(shù)中被切除掉大腦的大部分海馬后，便再也無(wú)法記住此后發(fā)生的任何事情。不過(guò)，他記得以前的事情，也能學(xué)習(xí)新技能和新詞匯。這表明，記憶新經(jīng)歷形成的“情節(jié)性”記憶與其他類型的認(rèn)知和記憶所需用到的大腦區(qū)域不同。逆行性失憶可由老年癡呆癥、腦外傷、維生素B1缺乏以及其他損傷等造成。但是，大腦的損傷并不會(huì)有選擇性地只破壞自傳體記憶(編者注：即關(guān)于個(gè)體自身所經(jīng)歷事件的記憶)，更別說(shuō)要找回這部分記憶了。

Men are from Mars， women are from Venus.

男人來(lái)自火星，女人來(lái)自金星。

Eminent19) neuroscientists once claimed that head size， spinal ganglia20) or brain stem structures were responsible for women's inability to think creatively， vote logically or practice medicine. Today the theories are a bit more sophisticated21): men supposedly have more specialized brain hemispheres22)， women more elaborate23) emotion circuits. Though there are some differences between male and female brains， the main problem with looking for correlations with behavior is that sex differences in cognition are massively exaggerated.

Women are thought to outperform men on tests of empathy24). They do—unless test subjects are told that men are particularly good at the test， in which case men perform as well as or better than women. The same pattern holds in reverse25) for tests of spatial reasoning. Whenever stereotypes are brought to mind， even by something as simple as asking test subjects to check a box next to their gender， sex differences are exaggerated. Women college students told that a test is something women usually do poorly on， do poorly. Women college students told that a test is something college students usually do well on， do well. Across countries—and across time—the more prevalent the belief is that men are better than women in math， the greater the difference in girls' and boys' math scores. And that's not because girls in Iceland have more specialized brain hemispheres than do girls in Italy.

Certain sex differences are enormously26) important to us when we're looking for a mate， but when it comes to most of what our brains do most of the time—perceive27) the world， direct attention， learn new skills， encode memories， communicate (no， women don't speak more than men do)， judge other people's emotions (no， men aren't inept28) at this)—men and women have almost entirely overlapping and fully earth-bound29) abilities.

一些知名神經(jīng)科學(xué)家曾聲稱，受限于腦袋大小、脊神經(jīng)節(jié)以及腦干結(jié)構(gòu)，女性無(wú)法創(chuàng)新思考、理性選舉或行醫(yī)治病。如今的理論則更為“高深”：據(jù)稱，男性的大腦半球?qū)I(yè)性更強(qiáng)，而女性的情感回路則更為復(fù)雜。男女大腦的確存在一些差別，但當(dāng)前男女行為與大腦相關(guān)性的研究所面臨的主要問(wèn)題是，人們?cè)谡J(rèn)識(shí)層面上過(guò)分夸大了男女的性別差異。

人們認(rèn)為女性在移情測(cè)試方面優(yōu)于男性。確實(shí)如此，除非受測(cè)者被告知男性特別擅長(zhǎng)這一測(cè)試。倘若真是那樣，男性的表現(xiàn)就會(huì)和女性一樣好或比女性好。在空間推理測(cè)試中這一情形正好相反。定勢(shì)思維一旦產(chǎn)生，即使只是要求受測(cè)者在性別一欄畫(huà)上對(duì)勾這樣簡(jiǎn)單的事情，性別差異就被夸大了。告訴女大學(xué)生說(shuō)女性在某項(xiàng)測(cè)試上通常成績(jī)很差，她們的測(cè)試成績(jī)就不理想；告訴女大學(xué)生說(shuō)女性在某項(xiàng)測(cè)試上通常成績(jī)優(yōu)秀，那她們就會(huì)取得優(yōu)秀的成績(jī)。無(wú)論是在哪個(gè)國(guó)家，無(wú)論是在什么時(shí)候，只要認(rèn)為男性比女性更擅長(zhǎng)數(shù)學(xué)的觀念越普遍，女孩和男孩的數(shù)學(xué)成績(jī)差異就越大，造成這種差異的原因絕不是冰島女孩比意大利女孩的大腦半球?qū)I(yè)性更強(qiáng)。

在我們尋找另一半時(shí)，了解某些性別差異極其重要。但是，若談到我們的大腦大部分時(shí)間所做的事情——感知世界、引導(dǎo)注意力、學(xué)習(xí)新技能、形成記憶、溝通交流(不，女人并不比男人愛(ài)說(shuō)話)、察言觀色(男人在這方面也并不笨手笨腳)，男女雙方的種種能力則幾近相同，再平凡不過(guò)了。

1.compelling [k#601;m#712;pel#618;#331;] adj. 令人信服的

2.untapped [#716;#652;n#712;taelig;pt] adj. 未開(kāi)發(fā)的，未利用的

3.vestigial [ve#712;st#618;d#658;i#601;l] adj. 殘留的，殘余的

4.appendix [#601;#712;pend#618;ks] n. 附屬物，附加物

5.fetal [#712;fi#720;tl] adj. 胎兒的

6.surplus [#712;s#604;#720;pl#601;s] adj. 過(guò)剩的，剩余的

7.autopsy [#712;#596;#720;t#594;psi] n. 尸體解剖

8.impaired [#618;m#712;pe#601;d] adj. 受損的

9.flashbulb memory: 閃光燈記憶，是指重要事件發(fā)生時(shí)，我們不僅能記住此事件，還能記住與此事件不直接相關(guān)的信息，如當(dāng)時(shí)的自己身處何地、與誰(shuí)在一起以及在做什么等細(xì)節(jié)。正如閃光燈一樣，我們不僅對(duì)閃光燈印象深刻，還能記住閃光燈照亮的區(qū)域。

10.muddled [#712;m#652;dld] adj. 混亂的；雜亂無(wú)章的

11.cognitive [#712;k#594;ɡn#601;t#618;v] adj. 認(rèn)知的，認(rèn)識(shí)過(guò)程的

12.conk [k#594;#331;k] n. 敲在頭(或鼻子等上)的一擊

13.amnesia [aelig;m#712;ni#720;zi#601;] n. 【醫(yī)】記憶缺失；遺忘(癥)

14.trope [tr#601;#650;p] n. 【語(yǔ)】轉(zhuǎn)義，比喻

15.hippocampus

[#716;h#618;p#601;#712;kaelig;mp#601;s] n. 【解】海馬(延伸于腦的每一個(gè)側(cè)腦室下角底上的一條海馬狀突起)

16.episodic memories: 情節(jié)記憶，對(duì)與一定的時(shí)間、地點(diǎn)及具體情境相聯(lián)系的事件的識(shí)記、保持和再現(xiàn)。

17.traumatic [tr#596;#720;#712;maelig;t#618;k] adj. 【醫(yī)】外傷(性)的，損傷(性)的

18.thiamine [#712;θa#618;#601;mi#720;n] n. 【生化】硫胺素，維生素B1

19.eminent [#712;em#618;n#601;nt] adj. 顯赫的，著名的

20.spinal ganglion: 【解】脊神經(jīng)節(jié)。spinal [#712;spa#618;nl] adj. 【解】脊的，脊柱的。ganglion [#712;ɡaelig;#331;ɡli#601;n] n. 【解】神經(jīng)節(jié)，其復(fù)數(shù)形式為ganglia

21.sophisticated

[s#601;#712;f#618;st#618;ke#618;t#618;d] adj. 深?yuàn)W微妙的

22.hemisphere [#712;hem#618;sf#618;#601;(r)] n. 【解】大腦半球

23.elaborate [#618;#712;laelig;b#601;r#601;t] adj. 復(fù)雜的；詳盡的

24.empathy [#712;emp#601;θi] n. 【心】感情移入，移情

25.reverse [r#618;#712;v#604;#720;s] n. 相反情況

26.enormously [#618;#712;n#596;#720;m#601;sli] adv. 巨大地，極大地

27.perceive [p#601;#712;si#720;v] vt. 感知，感覺(jué)；察覺(jué)

28.inept [#618;#712;nept] adj. 笨拙的；無(wú)能的

29.earth-bound [#712;#604;#720;θba#650;nd] adj. 缺乏想象力的，平凡的