明明挠的是别人，为啥自己会笑个不停

It’s perfectly normal for someone to laugh uncontrollably when tickled, although some of us are more ticklish than others, but researchers at the University of California, San Diego, recently reported the unusual case of a woman who would burst into laughter when seeing other people being tickled.

被人挠痒痒时，你会控制不住地笑个不停。这很正常。尽管每个人的敏感程度存在差异，但加州大学圣地亚哥分校的研究人员最近报告了一种非同寻常的病症：一位女性只要看到别人被挠痒痒，自己就会无法抑制地笑个不停。

Referred to only as TC, the woman was apparently seeking help for her bizarre condition – whenever she saw someone getting tickled, she could feel the sensation on her own skin and would start to laugh uncontrollably as if she was the one getting tickled. Researchers conducted a series of experiments to explore the bizarre phenomenon further and concluded that the woman suffered from a rare condition known as mirror-touch synaesthesia. It is believed to be caused by mirror neurons, connectors in the brain that react the same way when an event is experienced or when it’s simply observed.

他们称这位女性为TC。她因为自身的奇怪症状而寻求医学帮助。只要看到别人被挠痒痒，她就会在自己的皮肤上产生感觉，然后开始大笑不止，仿佛她才是被挠痒痒的那个人。为探究这种奇怪现象，研究人员进行了一系列实验，最后得出结论：她患有一种罕见症状——镜像触觉联觉。科学家认为，这是由“镜像神经元”引起的。镜像神经元是大脑里的一群神经细胞，能够在体验或仅仅观察某些事件时产生反应。

To make sure that TC’s fits of laughter were caused by mirror-touch synaesthesia and not because she simply found the situation of another person being tickled funny, researchers at the University of California, San Diego, tested the woman’s reactions in various circumstances, like seeing other people touch different surfaces, put their hand in ice water, or be tickled. They also tested her reactions to jokes and funny video clips, and established that she had a normal sense of humor.

她的症状是由镜像触觉联觉引起的，还是由于她觉得别人被挠痒痒的场景很滑稽?为探究此问题，研究人员在各种场景中测试她的反应，例如看到他人触碰不同物体的表面、把手放进冰水里、被挠痒痒等。此外，他们也测试了她对笑话和搞笑视频的反应，证实她具有正常的幽默感。

The study showed that whenever she watched other people getting tickled, TC reacted with uncontrollable laughter, as if she was experiencing the tickling herself. The sensation was so realistic that she would rub her armpits in an attempt to neutralize it.

研究结果显示：只要看到别人被挠痒痒，她就会无法抑制地笑个不停，仿佛自己正被人挠痒痒。她的感觉非常真实，以至于她会摩擦自己的腋窝，企图缓解这种感觉。

The reaction to second-hand tickling was more intense under certain circumstances. For example, the tickling sensation appeared to be considerably more acute when TC could see the facial expressions of the volunteers being tickled during the experiments, or if the volunteer was someone she knew, or who looked like her. Researchers note that the laughter was most extreme when she watched videos of herself being tickled.

在某些情况下，这种反应会更加剧烈，例如：当她看到志愿者(被挠痒痒者)的面部表情时;当志愿者是她认识的人时;当志愿者和她长相类似时。在观看自己被挠痒痒的视频时，她的反应最为剧烈。

Similar results were recorded in experiments where TC watched other people touching velvet, brushes, silk, and table surfaces. She reported experiencing the same sensations as if she was the one touching them. When seeing volunteers dunk their hand in ice water, she reported feeling the wet sensation but not the low temperature.

当她看到志愿者触摸天鹅绒、刷子、丝绸、桌子等物体的表面时，她也会产生同样的触感，仿佛自己正在触摸它们。当她看到志愿者将手放进冰水里时，她会产生湿润感，但没有产生低温感。

Researchers explained that mirror neurons in TC’s brain worked a bit differently than they do in most people’s brains. These connectors are activated when we or someone we see is being touched, but the brain usually blocks their response when it’s someone else experiencing the sensation, essentially separating the self from others. In TC’s case, the blocking signals sent by her brain are weaker, which causes her to experience other people’s sensations as if they were her own.

研究人员解释道，她的镜像神经元和常人略有不同。当我们自身被触碰或我们看到某人被触碰时，这些神经元会被激活。不过，在第二种情况下，大脑通常会封锁反应，以区分自我和他人。但她的封锁信号比较弱，这导致她能够真实地体验到他人的触感。

Studies suggest that only between 1.6% and 2.5% of the human population experience some form of mirror-touch synesthesia, but the degree of empathy can vary greatly, as can the sensations.

研究显示，只有1.6-2.5%的人会体验到某种形式的镜像触觉联觉，但程度和感觉存在极大差异。