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）在洗澡时发现浮力定律；笛卡尔（Descartes）躺在床上看天花板上的苍蝇，领悟坐标几何原理；牛顿（Newton）在果园看到苹果从树上掉下来，提出万有引力定律。这三个人都有刹那间的灵感之光。

在科学与发现的故事中，顿悟发挥着至关重要的作用，并且可遇而不可求。正是由于这种顿悟，人类社会才会有那么多新发明和新发现，大到交流电理论和青霉素，小到报事帖（Post-it）、甜筒冰激凌和维可牢尼龙刺粘扣（Velcro）.智慧之光爆发出的力量是如此强大，以至于传说中阿基米德从浴缸中跳出来，一丝不挂地跑到街上，对着惊讶的邻居们大喊："尤里卡！尤里卡（我找到了）!"

在今天这个鼓励创新的经济环境中，工程师、经济学家和政府官员都热切盼望能在知识工作者群体中培养一种创新思维能力。以前，那些灵感故事的真实性在严肃科学研究领域得不到认可。学者们怀疑，阿基米德的故事可能出于杜撰。然而，最近研究人员在一些志愿者做文字游戏、谜语和其他智力测试时进行脑电波检查和神经网络成像，从而记录下灵感迸发刹那的脑部状况。

通过跟踪脑部面对智力挑战时的表现，科学家正试图深入了解灵感闪现瞬间的脑部状况，但是在临床上很难对这些脑部变化进行界定，其难度不亚于在实验室内对这些脑部变化进行研究的过程。

诚然，每个人都有过"对了！"的那一瞬间。这种灵感的来临毫无征兆，往往是思维在潜意识中发生不自觉的变化，从而突然扭转我们看待问题的角度。"灵感是一种突然间的领悟，让你看到一些平时没有发现的东西。"费城德雷塞尔大学（Drexel University）的心理学家约翰？库尼奥斯（John Kounios）说，"灵感可能让你解开一个难题，想出一个笑话，突然认出一张脸来；也可能让你意识到，自己的一个朋友其实并不算得上真正的朋友。"

研究人员发现，这种突如其来的顿悟是一连串强烈而复杂的脑部反应积累后的迸发，与系统的推理相比，这种状况的产生需要更多的神经活动。与利用分析方法解决问题的人相比，通过顿悟来解决问题的人产生一种不同的脑电波图形。"在顿悟来临前的那一刻，你的脑部在剧烈运转。"匹兹堡大学（University of Pittsburgh）的心理学家马克？维勒（Mark Wheeler）说，"就像在宁静的水面下，是一股股的湍流。"

事实上，一项新的脑部扫描研究显示，我们在走神时，即在不知道自己在想什么的时候，脑部活动可能是最剧烈的。"以灵感来解决问题与以分析来解决问题具有本质上的区别。" 库尼奥斯博士说，"这牵涉到不同的脑部运行机制。"在大多数情况下，人每天有三分之一的时间是在做白日梦，而就在这些看似悠闲的时刻，我们的脑部通常都处于非常活跃的状态。在思维天马行空之时，脑部几个与解决复杂问题相关的区域得到启动。研究人员以前认为，这几个脑部区域在人走神时是处于休眠状态的，但恰恰相反，研究表明这些区域只有在走神时才会共同工作。

"人们以为自己走神时脑子不在动，"位于温哥华的英属哥伦比亚大学（University of British Columbia in Vancouver）的认知神经学家凯莉娜？克里斯托弗（Kalina Christoff）说，通过对脑部活动的监测，其实"走神状态时，脑部的活跃程度远超我们的想象，比用推理来解决复杂问题时活跃得多。"克里斯托弗于2009年5月在《美国科学院院报》（Proceedings of the National Academy of Sciences）上发表了自己的这项研究成果。

克里斯托弗怀疑，人的脑子在走神时，可能会比理性思考时产生更多的新主意，出现更多出乎意料的思维融合。这也许为新思想的诞生创造了一个精神平台。"可以看到，在灵感迸发前，神经网络的一些区域会变得十分活跃。" 克里斯托弗说道。

过去五年来，通过一系列的实验，库尼奥斯教授与其合作者、美国西北大学（Northwestern University）的马克？强比曼（Mark Jung-Beeman）利用脑部扫描仪和脑电图（EEG）传感器来研究表层自我意识底下的灵感起源。他们记录下志愿者在绞尽脑汁解决字谜时的神经活动，并扫描他们解出字谜时的脑部状态。

有些志愿者通过系统分析法得出问题的答案，有些则一筹莫展；还有一部分人，虽然答案好像是凭空得来的，但他们坚信答案准确无误。

在最后这部分人的研究中，脑电图显示他们的右半脑--即负责处理问题相关性和相似要素的区域--发射出一种特殊的伽玛波（gamma wave）.在脑部发射这种信号波三分之一秒后，志愿者就会发生顿悟。

也许，科学家已经首次记录下灵感产生的一瞬间。"脑电波的出现与人们意识到问题解决方案的那一刹那几乎重合。" 库尼奥斯教授说道。

另外他们还发现，在伽玛波爆发前，几乎总伴随着控制视觉的脑部视觉皮质中阿尔法脑电波（alpha brain-wave）的强度变化。这表明，脑部在灵感发生前有意抑制神经细胞的活跃度，就像我们集中注意力时会有意识地闭上双眼一样。

"这是为了降低脑子里的杂音，保护好新思想的萌芽。"西北大学的强比曼教授说道。

在英国伦敦戈德史密斯大学（University of London's Goldsmith College）,心理学家乔伊迪普？巴塔查亚（Joydeep Bhattacharya）也在研究人们在解谜时的灵感迸发时刻。在试验前，他挑选出通过灵感来解开谜语的人。通过脑电波监测，他发现这些人在解开谜语之前，其右额叶皮质会出现一种高频率的神经活动，通常在得出答案的八秒钟甚至更短的时间内发生。巴塔查亚教授在最新一期《认知神经科学杂志》（Journal of Cognitive Neuroscienc）上发表了上述研究成果。

"这还是个谜，" 巴塔查亚教授说，"我们的脑袋知道这是怎么回事，但我们自己不知道。"

到目前为止，还没人知道为什么问题有时会引发顿悟，以及为什么顿悟有些时候更容易产生。但有一点研究人员可以肯定，顿悟青睐有准备的人。

我们碰到问题之前的精神状态也会影响到我们能否依靠灵感来解决问题的能力。德雷塞尔大学和西北大学的研究人员发现，精神状态积极正面的人更容易产生灵感。"你面对问题前的思想状况将影响自己解决问题的能力。" 强比曼教授说。通过对灵感迸发时刻的深入分析，研究人员希望找到脑组织怎么会产生新想法的线索。"灵感对智者来说至关重要。" 巴塔查亚教授说道。

上述这些研究成果表明人类精神生活中存在的悖论，提醒我们关注一个事实，即人类的创新思维来自于神经细胞和神经化学反应，既在自觉意识的范畴之外，又不受我们的直接控制。

"我们往往以为，没有自己的主动关注，思维就不存在。"温哥华的克里斯托弗教授说，"其实当我们不关注时，可能正是思维最具创意的时刻。"