人类的眼睛根本不会传递欢乐！

诗人和音乐家听到这个消息一定会垮掉：人类的眼睛根本不会传递欢乐。利用蒙娜丽莎肖像进行的一项新的研究显示，眼睛同样也无法传递悲伤的情绪。实际上这两种表情都是由嘴部运动产生的。类似的研究还有助于确定其他一些表情产生的机制，或者有助于搞清由于视觉问题造成的大脑缺陷，例如缺乏辨认面孔的能力。

人类的面部表情比看上去的还要微妙，并且很难确定这些情感信息的来源。研究人员通常使用的一种技术就是向志愿者展示一部分面孔，然后询问他们看到了什么样的表情。另一种不同的技术则是让表情在一幅图像上不断“演变”，使研究人员能够在很短的时间里对全部的表情进行研究。

为了搞清究竟是什么面部特征使人显得高兴或悲伤，美国旧金山Smith-Kettlewell视觉研究所的视觉神经学家Christopher Tyler和Leonid Kontsevich对蒙娜丽莎的面部表情进行了演化。研究人员对蒙娜丽莎暧昧的表情进行了干扰，使图像看上去就像模糊的电视屏幕一样，然后让受试者按照从高兴到悲伤的４个类别评估蒙娜丽莎的表情。研究人员随后对每一种表情的全部干扰图像进行了分类，揭示出传递欢乐与悲伤表情的面部特征的细微区别。为了搞清眼睛与嘴巴是否在形成表情的过程中同时起了作用，研究小组将蒙娜丽莎面孔的上部或下部分别用合成的欢乐或悲伤的干扰图像进行了替换。当覆盖住蒙娜丽莎的眼睛后，可以看出画中的人物在微笑或蹙额，而当遮盖住蒙娜丽莎的嘴巴后，则传达不出任何感情。研究人员将这一发现通过一个带有暧昧表情的妇女图像复制下来。

Tyler表示，“眼睛通常被当作心灵的窗口，因此我们希望能够看到眼睛在表情的形成过程中所起的作用”。他推测，实际上，眼睛或许能够传递感情的强弱。费城宾夕法尼亚大学的视觉心理学家Richard MurrayＲ同样对这一研究结果感到惊讶，“它们或许是心灵的窗口”。他指出，除了了解有关表情的问题外，“我们还可以利用这项技术对人类的视觉缺陷进行研究，从而了解我们的大脑究竟在哪里出现了错误”。

以下为原版文字：

Poets and songwriters will be devastated to hear it: The eyes don't smile after all. Neither do they sadden, according to new research using Mona Lisa's portrait. Those two emotions are the domain of the mouth, it turns out. Similar research could help pinpoint other emotions, or help determine the brain defects in people with visual problems such as the inability to recognize faces.

Happy or not? It all depends on the pattern of random noise over The Mona Lisa's mouth.
CREDIT: L. L. KONTSEVICH AND C. W. TYLER, VISION RESEARCH 44, 1496
Human facial expressions are subtler than they look, and it's hard to determine the source of emotional information. One technique researchers have used is to show volunteers parts of a face and ask what emotion they see. A different technique allows expressions to "evolve" on an image, allowing researchers access to the whole expression at once.

To determine what features make people look happy or sad, visual neuroscientists Christopher Tyler and Leonid Kontsevich of the Smith-Kettlewell Eye Research Institute in San Francisco evolved expressions on The Mona Lisa. The researchers added noise to her ambiguous expression, making the image look like a fuzzy TV screen, then asked subjects to rate her emotion on a four-point scale of happy to sad. The researchers then averaged all of the noisy images in each category of emotion, revealing the subtleties in the facial features needed to spell out happiness or sadness. To determine whether the eyes and the mouth worked together to evoke emotion, the team laid the composite happy or sad noise on just the upper or lower half at a time. Overlaying the mouth half caused Mona to grin or frown, but overlaying the eyes conveyed no emotion. The researchers replicated the finding with a photograph of a woman with an ambiguous expression.

"The eyes are well-known to be the window on the soul, so we expected to see an effect of the eyes," says Tyler. Instead, the eyes might express intensity, he speculates. "Perhaps they are the window on the spirit." Visual psychophysicist Richard Murray of the University of Pennsylvania in Philadelphia is also surprised. In addition to learning about expressions, "we can use this technique on people with visual deficits to determine what's going wrong in their brain," he says.

--MARY BECKMAN