It happened to Archimedes in the bath. To Descartes it took place in bed while watching flies on his ceiling. And to Newton it occurred in an orchard, when he saw an apple fall. Each had a moment of insight. To Archimedes came a way to calculate density and volume; to Descartes, the idea of coordinate geometry; and to Newton, the law of universal gravity.

    In our fables of science and discovery, the crucial role of insight is a cherished theme. To these epiphanies, we owe the concept of alternating electrical current, the discovery of penicillin, and on a less lofty note, the invention of Post-its, ice-cream cones, and Velcro. The burst of mental clarity can be so powerful that, as legend would have it, Archimedes jumped out of his tub and ran naked through the streets, shouting to his startled neighbors: 'Eureka! I've got it.'

    In today's innovation economy, engineers, economists and policy makers are eager to foster creative thinking among knowledge workers. Until recently, these sorts of revelations were too elusive for serious scientific study. Scholars suspect the story of Archimedes isn't even entirely true. Lately, though, researchers have been able to document the brain's behavior during Eureka moments by recording brain-wave patterns and imaging the neural circuits that become active as volunteers struggle to solve anagrams, riddles and other brain teasers.

    Following the brain as it rises to a mental challenge, scientists are seeking their own insights into these light-bulb flashes of understanding, but they are as hard to define clinically as they are to study in a lab.

    To be sure, we've all had our 'Aha' moments. They materialize without warning, often through an unconscious shift in mental perspective that can abruptly alter how we perceive a problem. 'An 'aha' moment is any sudden comprehension that allows you to see something in a different light,' says psychologist John Kounios at Drexel University in Philadelphia. 'It could be the solution to a problem; it could be getting a joke; or suddenly recognizing a face. It could be realizing that a friend of yours is not really a friend.'

    These sudden insights, they found, are the culmination of an intense and complex series of brain states that require more neural resources than methodical reasoning. People who solve problems through insight generate different patterns of brain waves than those who solve problems analytically. 'Your brain is really working quite hard before this moment of insight,' says psychologist Mark Wheeler at the University of Pittsburgh. 'There is a lot going on behind the scenes.'

    In fact, our brain may be most actively engaged when our mind is wandering and we've actually lost track of our thoughts, a new brain-scanning study suggests. 'Solving a problem with insight is fundamentally different from solving a problem analytically,' Dr. Kounios says. 'There really are different brain mechanisms involved.' By most measures, we spend about a third of our time daydreaming, yet our brain is unusually active during these seemingly idle moments. Left to its own devices, our brain activates several areas associated with complex problem solving, which researchers had previously assumed were dormant during daydreams. Moreover, it appears to be the only time these areas work in unison.

    'People assumed that when your mind wandered it was empty,' says cognitive neuroscientist Kalina Christoff at the University of British Columbia in Vancouver, who reported the findings last month in the Proceedings of the National Academy of Sciences. As measured by brain activity, however, 'mind wandering is a much more active state than we ever imagined, much more active than during reasoning with a complex problem.'

    She suspects that the flypaper of an unfocused mind may trap new ideas and unexpected associations more effectively than methodical reasoning. That may create the mental framework for new ideas. 'You can see regions of these networks becoming active just prior to people arriving at an insight,' she says.

    In a series of experiments over the past five years, Dr. Kounios and his collaborator Mark Jung-Beeman at Northwestern University used brain scanners and EEG sensors to study insights taking form below the surface of self-awareness. They recorded the neural activity of volunteers wrestling with word puzzles and scanned their brains as they sought solutions.

    Some volunteers found answers by methodically working through the possibilities. Some were stumped. For others, even though the solution seemed to come out of nowhere, they had no doubt it was correct.

    In those cases, the EEG recordings revealed a distinctive flash of gamma waves emanating from the brain's right hemisphere, which is involved in handling associations and assembling elements of a problem. The brain broadcast that signal one-third of a second before a volunteer experienced their conscious moment of insight -- an eternity at the speed of thought.

    The scientists may have recorded the first snapshots of a Eureka moment. 'It almost certainly reflects the popping into awareness of a solution,' says Dr. Kounios.

    In addition, they found that tell-tale burst of gamma waves was almost always preceded by a change in alpha brain-wave intensity in the visual cortex, which controls what we see. They took it as evidence that the brain was dampening the neurons there similar to the way we consciously close our eyes to concentrate.

    'You want to quiet the noise in your head to solidify that fragile germ of an idea,' says Dr. Jung-Beeman at Northwestern.

    At the University of London's Goldsmith College, psychologist Joydeep Bhattacharya also has been probing for insight moments by peppering people with verbal puzzles. By monitoring their brain waves, he saw a pattern of high frequency neural activity in the right frontal cortex that identified in advance who would solve a puzzle through insight and who would not. It appeared up to eight seconds before the answer to a problem dawned on the test subject, Dr. Bhattacharya reported in the current edition of the Journal of Cognitive Neuroscience.

    'It's unsettling,' says Dr. Bhattacharya. 'The brain knows but we don't.'

    So far, no one knows why problems sometimes trigger an insight or what makes us more inclined to the Eureka experience at some moments but not at others. Insight does favor a prepared mind, researchers determined.

    Even before we are presented with a problem, our state of mind can affect whether or not we will likely resort to insightful thinking. People in a positive mood were more likely to experience an insight, researchers at Drexel and Northwestern found. 'How you are thinking beforehand is going to affect what you do with the problems you get,' Dr. Jung-Beeman says. By probing the anatomy of 'aha,' researchers hope for clues to how brain tissue can manufacture a new idea. 'Insight is crucial to intellect,' Dr. Bhattacharya says.

    Taken together, these findings highlight a paradox of mental life. They remind us that much of our creative thought is the product of neurons and nerve chemistry outside our awareness and beyond our direct control.

    'We often assume that if we don't notice our thoughts they don't exist,' says Dr. Christoff in Vancouver, 'When we don't notice them is when we may be thinking most creatively.'

    阿基米德（Archimedes）在洗澡時發(fā)現(xiàn)浮力定律；笛卡爾（Descartes）躺在床上看天花板上的蒼蠅，領(lǐng)悟坐標幾何原理；牛頓（Newton）在果園看到蘋果從樹上掉下來，提出萬有引力定律。這三個人都有剎那間的靈感之光。

    在科學(xué)與發(fā)現(xiàn)的故事中，頓悟發(fā)揮著至關(guān)重要的作用，并且可遇而不可求。正是由于這種頓悟，人類社會才會有那么多新發(fā)明和新發(fā)現(xiàn)，大到交流電理論和青霉素，小到報事帖（Post-it）、甜筒冰激凌和維可牢尼龍刺粘扣（Velcro）.智慧之光爆發(fā)出的力量是如此強大，以至于傳說中阿基米德從浴缸中跳出來，一絲不掛地跑到街上，對著驚訝的鄰居們大喊："尤里卡！尤里卡（我找到了）!"

    在今天這個鼓勵創(chuàng)新的經(jīng)濟環(huán)境中，工程師、經(jīng)濟學(xué)家和政府官員都熱切盼望能在知識工作者群體中培養(yǎng)一種創(chuàng)新思維能力。以前，那些靈感故事的真實性在嚴肅科學(xué)研究領(lǐng)域得不到認可。學(xué)者們懷疑，阿基米德的故事可能出于杜撰。然而，最近研究人員在一些志愿者做文字游戲、謎語和其他智力測試時進行腦電波檢查和神經(jīng)網(wǎng)絡(luò)成像，從而記錄下靈感迸發(fā)剎那的腦部狀況。

    通過跟蹤腦部面對智力挑戰(zhàn)時的表現(xiàn)，科學(xué)家正試圖深入了解靈感閃現(xiàn)瞬間的腦部狀況，但是在臨床上很難對這些腦部變化進行界定，其難度不亞于在實驗室內(nèi)對這些腦部變化進行研究的過程。

    誠然，每個人都有過"對了！"的那一瞬間。這種靈感的來臨毫無征兆，往往是思維在潛意識中發(fā)生不自覺的變化，從而突然扭轉(zhuǎn)我們看待問題的角度。"靈感是一種突然間的領(lǐng)悟，讓你看到一些平時沒有發(fā)現(xiàn)的東西。"費城德雷塞爾大學(xué)（Drexel University）的心理學(xué)家約翰？庫尼奧斯（John Kounios）說，"靈感可能讓你解開一個難題，想出一個笑話，突然認出一張臉來；也可能讓你意識到，自己的一個朋友其實并不算得上真正的朋友。"

    研究人員發(fā)現(xiàn)，這種突如其來的頓悟是一連串強烈而復(fù)雜的腦部反應(yīng)積累后的迸發(fā)，與系統(tǒng)的推理相比，這種狀況的產(chǎn)生需要更多的神經(jīng)活動。與利用分析方法解決問題的人相比，通過頓悟來解決問題的人產(chǎn)生一種不同的腦電波圖形。"在頓悟來臨前的那一刻，你的腦部在劇烈運轉(zhuǎn)。"匹茲堡大學(xué)（University of Pittsburgh）的心理學(xué)家馬克？維勒（Mark Wheeler）說，"就像在寧靜的水面下，是一股股的湍流。"

    事實上，一項新的腦部掃描研究顯示，我們在走神時，即在不知道自己在想什么的時候，腦部活動可能是最劇烈的。"以靈感來解決問題與以分析來解決問題具有本質(zhì)上的區(qū)別。" 庫尼奧斯博士說，"這牽涉到不同的腦部運行機制。"在大多數(shù)情況下，人每天有三分之一的時間是在做白日夢，而就在這些看似悠閑的時刻，我們的腦部通常都處于非�；钴S的狀態(tài)。在思維天馬行空之時，腦部幾個與解決復(fù)雜問題相關(guān)的區(qū)域得到啟動。研究人員以前認為，這幾個腦部區(qū)域在人走神時是處于休眠狀態(tài)的，但恰恰相反，研究表明這些區(qū)域只有在走神時才會共同工作。

    "人們以為自己走神時腦子不在動，"位于溫哥華的英屬哥倫比亞大學(xué)（University of British Columbia in Vancouver）的認知神經(jīng)學(xué)家凱莉娜？克里斯托弗（Kalina Christoff）說，通過對腦部活動的監(jiān)測，其實"走神狀態(tài)時，腦部的活躍程度遠超我們的想象，比用推理來解決復(fù)雜問題時活躍得多。"克里斯托弗于2009年5月在《美國科學(xué)院院報》（Proceedings of the National Academy of Sciences）上發(fā)表了自己的這項研究成果。

    克里斯托弗懷疑，人的腦子在走神時，可能會比理性思考時產(chǎn)生更多的新主意，出現(xiàn)更多出乎意料的思維融合。這也許為新思想的誕生創(chuàng)造了一個精神平臺。"可以看到，在靈感迸發(fā)前，神經(jīng)網(wǎng)絡(luò)的一些區(qū)域會變得十分活躍。" 克里斯托弗說道。

    過去五年來，通過一系列的實驗，庫尼奧斯教授與其合作者、美國西北大學(xué)（Northwestern University）的馬克？強比曼（Mark Jung-Beeman）利用腦部掃描儀和腦電圖（EEG）傳感器來研究表層自我意識底下的靈感起源。他們記錄下志愿者在絞盡腦汁解決字謎時的神經(jīng)活動，并掃描他們解出字謎時的腦部狀態(tài)。

    有些志愿者通過系統(tǒng)分析法得出問題的答案，有些則一籌莫展；還有一部分人，雖然答案好像是憑空得來的，但他們堅信答案準確無誤。

    在最后這部分人的研究中，腦電圖顯示他們的右半腦--即負責處理問題相關(guān)性和相似要素的區(qū)域--發(fā)射出一種特殊的伽瑪波（gamma wave）.在腦部發(fā)射這種信號波三分之一秒后，志愿者就會發(fā)生頓悟。

    也許，科學(xué)家已經(jīng)首次記錄下靈感產(chǎn)生的一瞬間。"腦電波的出現(xiàn)與人們意識到問題解決方案的那一剎那幾乎重合。" 庫尼奧斯教授說道。

    另外他們還發(fā)現(xiàn)，在伽瑪波爆發(fā)前，幾乎總伴隨著控制視覺的腦部視覺皮質(zhì)中阿爾法腦電波（alpha brain-wave）的強度變化。這表明，腦部在靈感發(fā)生前有意抑制神經(jīng)細胞的活躍度，就像我們集中注意力時會有意識地閉上雙眼一樣。

    "這是為了降低腦子里的雜音，保護好新思想的萌芽。"西北大學(xué)的強比曼教授說道。

    在英國倫敦戈德史密斯大學(xué)（University of London's Goldsmith College）,心理學(xué)家喬伊迪普？巴塔查亞（Joydeep Bhattacharya）也在研究人們在解謎時的靈感迸發(fā)時刻。在試驗前，他挑選出通過靈感來解開謎語的人。通過腦電波監(jiān)測，他發(fā)現(xiàn)這些人在解開謎語之前，其右額葉皮質(zhì)會出現(xiàn)一種高頻率的神經(jīng)活動，通常在得出答案的八秒鐘甚至更短的時間內(nèi)發(fā)生。巴塔查亞教授在最新一期《認知神經(jīng)科學(xué)雜志》（Journal of Cognitive Neuroscienc）上發(fā)表了上述研究成果。

    "這還是個謎，" 巴塔查亞教授說，"我們的腦袋知道這是怎么回事，但我們自己不知道。"

    到目前為止，還沒人知道為什么問題有時會引發(fā)頓悟，以及為什么頓悟有些時候更容易產(chǎn)生。但有一點研究人員可以肯定，頓悟青睞有準備的人。

    我們碰到問題之前的精神狀態(tài)也會影響到我們能否依靠靈感來解決問題的能力。德雷塞爾大學(xué)和西北大學(xué)的研究人員發(fā)現(xiàn)，精神狀態(tài)積極正面的人更容易產(chǎn)生靈感。"你面對問題前的思想狀況將影響自己解決問題的能力。" 強比曼教授說。通過對靈感迸發(fā)時刻的深入分析，研究人員希望找到腦組織怎么會產(chǎn)生新想法的線索。"靈感對智者來說至關(guān)重要。" 巴塔查亞教授說道。

    上述這些研究成果表明人類精神生活中存在的悖論，提醒我們關(guān)注一個事實，即人類的創(chuàng)新思維來自于神經(jīng)細胞和神經(jīng)化學(xué)反應(yīng)，既在自覺意識的范疇之外，又不受我們的直接控制。

    "我們往往以為，沒有自己的主動關(guān)注，思維就不存在。"溫哥華的克里斯托弗教授說，"其實當我們不關(guān)注時，可能正是思維最具創(chuàng)意的時刻。"