据《自然》13日报道，一项新的研究显示，笑声的确是可以传染的。研究人员已经证实，笑声会“胳肢”听者大脑的同一个区域——微笑的时候处于活跃状态。听者大脑的反应会帮助面部肌肉展现发自内心的笑容。研究报告联合执笔人、英国伦敦大学学院神经科学家索菲·斯科特(Sophie Scott)表示：“事实可能确实如此，正如谚语所说的那样：‘你笑，人人陪你笑。’”
研究人员分别向志愿者播放两组不同的声音，一组令人愉快——例如笑声和欢呼声；一组令人讨厌——例如尖叫和呕吐声。在此之后，他们利用功能磁共振成像(MRI)技术对志愿者的大脑进行监视。结果发现，所有这些声音都触发了大脑运动前皮层的神经反应。(运动前皮层是“部署”多组脸部肌肉作出相应反应的一个大脑区域。)当参与者确实微笑或者大笑的时候，这一神经活动便向初级运动皮层区“蔓延”。
研究小组报告说，运动前皮层对令人愉快的声音的神经反应强度平均是令人讨厌的声音的两倍。这一发现说明，愉快声音对刺激肌肉作出反应的大脑区域的影响更大，也就是说，愉快的声音比讨厌的声音更具“传染性”。此项研究报告刊登在本周出版的《神经科学杂志》上。
斯科特表示，这些研究发现是有重要意义的，因为它们提示人们，人类大脑中的“笑声触发装置”是“非常基本的或者说无意识的”。也就是说，人们听到愉快的声音时基本上是无法控制微笑或者大笑的冲动的。一个明显的例子就是：正在开一个令人厌烦的会议的人费力地抑制着他们想笑的欲望，一旦有一个人发出吱吱声，整个会议立即会变成笑声的海洋。
斯科特说，人类是已知的容易受身边人的行为或情绪“传染”动物。朋友经常是从使用相同的词眼、摆出类似的姿势和模仿类似的手势开始的。好与坏的情绪的“传染性”已是人所共知的事情。
斯科特表示，大脑的神经反应——对于听到愉快声音的人来说，这种反应是无意识的，而且是预先准备好的——可以帮助人们在社交中建立相互影响，营造彼此之间牢固的关系。她解释说：“在群体环境中，我们经常遇到积极的情绪，比如笑声或者欢呼声。”
斯科特等人的研究与先前的一些研究不谋而合，此前的研究人员已用实例说明了简单的刺激与更为复杂的情绪之间的关系。强迫微笑实际上可以提高一个人的情绪。对大脑一些区域的刺激也至少让一个病人发笑。
斯科特表示，作为一名拥有一个5月大儿子的母亲，自己拥有很多有关这个触发装置的第一手资料。她说，家里任何一个人的笑声都可能带动其他所有人笑起来。最有意思的是，斯科特对儿子笑，儿子也会对她笑，但打哈欠就没有这种待遇了。斯科特的研究小组并未在研究中使用有关打哈欠的声音和图片，但她同样对打哈欠是否也会传染产生了兴趣。
英文原文：
Laugh And The Whole World Laughs With You -- Why The Brain Just Can't Help Itself
Cricket commentator Jonathan Agnew's description of Ian Botham's freak dismissal, falling over his own stumps - "He couldn't quite get his leg over" - was all it took to send himself and the late Brian Johnston into paroxysms of laughter. Laughter is truly contagious, and now, scientists studying how our brain responds to emotive sounds believe they understand why.
Researchers at UCL (University College London) and Imperial College London have shown that positive sounds such as laughter or a triumphant "woo hoo!" trigger a response in the listener's brain. This response occurs in the area of the brain that is activated when we smile, as though preparing our facial muscles to laugh. The research, funded by the Wellcome Trust, Action Medical Research and the Barnwood House Trust, is published in the Journal of Neuroscience.
"It seems that it's absolutely true that 'laugh and the whole world laughs with you'," says Dr Sophie Scott, a Wellcome Trust Senior Research Fellow at the Institute of Cognitive Neuroscience, UCL. "We've known for some time now that when we are talking to someone, we often mirror their behaviour, copying the words they use and mimicking their gestures. Now we've shown that the same appears to apply to laughter, too - at least at the level of the brain."
The research team played a series sounds to volunteers whilst measuring their brain's response using an fMRI scanner. Some of the sounds were positive, such as laughter or triumph, whilst others were unpleasant, such as screaming or retching. All of the sounds triggered a response in the volunteer's brain in the premotor cortical region, which prepares the muscles in the face to respond accordingly, though the response was greater for positive sounds, suggesting that these were more contagious than negative sounds. The researchers believe this explains why we respond to laughter or cheering with an involuntary smile.
"We usually encounter positive emotions, such as laughter or cheering, in group situations, whether watching a comedy programme with family or a football game with friends," says Dr Scott. "This response in the brain, automatically priming us to smile or laugh, provides a way of mirroring the behaviour of others, something which helps us interact socially. It could play an important role in building strong bonds between individuals in a group."
So, if you want Christmas with the extended family to go swimmingly, maybe you should switch off Eastenders and dig out your Only Fools and Horses DVDs.
