If humans can indeed smell fear they wouldn’t be unusual in the animal kingdom. Sea anemones, earthworms, minnows, fruit flies, rats, mice, and deer, among others, have all been shown to signal unease through odor. Some responses are even more overt. For example, the offspring of one bird species vomits up a pungent, orange liquid when frightened by a predator; if a parent catches a whiff, it becomes warier in the nest.
恐惧的味道，我们真的能闻到么？不过就算我们能够闻到恐惧，在动物王国里，这也算不上稀奇。海葵、蚯蚓、米诺鱼、果蝇、大老鼠、小老鼠、鹿等动物都能通过气味传递警觉信号,除了气味，这些动物还有其它更为隐蔽的方法。比如，某种鸟类的幼崽会被天敌惊吓，呕吐出一种黄色液体，如果作为父母的鸟闻到了这种气息，便会警觉起来。

From an evolutionary perspective, a silent signal makes sense. “If you find yourself in a fearful situation, you might want your cohorts to know about it, but without calling attention to yourself by screaming or jumping around,” says Charles J. Wysocki, of the Monell Chemical Senses Center in Philadelphia. The same could hold true for humans. “Primates have become much more visual creatures [over time],” he says, “and I suspect that smell in general, including the perception of the fearful notes, have taken second place. But they’re still there.”
从进化论的角度来看，无声信号是很有用的。“如果你觉得自己的处境很惊险，你肯定希望你的同伴也获悉这一点，怎么通知呢，在这种情况下你是不想高声尖叫或是跳来跳去的。”费城莫奈尔化学感应研究中心的Charles J. Wysocki说其实人类何尝不是如此。“灵长类动物现在已经进化成非常依赖视觉的动物，”他说，“我认为除了视觉，嗅觉是灵长类动物中第二重要的感官，虽然是第二，但并没有消失。”

There’s only modest evidence for a smell of fear in people, though. No one has yet found a molecule in human sweat that corresponds to our level of anxiety. Several labs have tried to measure the effects of sniffing someone else’s fear-inspired body odor. First the scientists show people scary movies, and then they collect the subjects’ sweat from cotton pads placed in their armpits. When other people smell the cotton, they respond in subtle and unconscious ways. In one experiment, the smellers became more likely to judge ambiguous facial expressions in photographs as portraying fear. In another, they made fearful expressions of their own. A third found that fear-sniffing subjects blinked more forcefully and seemed more prone to being defensive.

虽然只有少数证据显示人类能在恐惧状态下释放出气味，而且至今我们也没有发现汗液中有任何一种分子和担惊受怕有关。为了验证这个谜题，科学家曾经做过一些实验，他们让一些实验对象闻另一些人在恐惧状况下散发的味道，并衡量气味的有效程度。这个实验中，科学家首先让实验对象看恐怖片，随后科学家将事先放置在他们腋窝处的棉签收集起来。另一组人呢，就负责闻这些胳肢窝分泌的汗水，结果这些人的反应不但微妙，而且属于无意识反应。闻味试验也分成三组，第一组实验对象闻了这些汗水后，认为某些模糊的面部表情描绘的是惊恐的表情；第二组中，闻了汗水的实验对象自己也表现出惊恐的表情；第三组实验中，研究人员发现闻了这些汗水的实验对象眨眼更用力，看似更具防卫倾向。

These studies have some big problems. Sweat born from emotion does seem to have a different smell than sweat from exercise. But that doesn’t tell us whether fear-related sweat works differently from, say, happiness-related sweat or the sweat that comes from sexual arousal. “We’re using very crude techniques to study this,” says Denise Chen, a pioneer in this field at the Baylor College of Medicine. Among the limitations of the work is the fact that emotions can be hard to regulate in the lab. “It’s very easy to scare people,” she says, “but it’s not so easy to make them happy.”
但是，这些研究都存在一些重大缺陷。不同情绪下分泌的汗水看似确实和运动时的汗水味道不一样。但是这些实验没有告诉人们恐惧汗水与快乐汗水、或者性冲动时的汗水是否有所不同。贝勒医学院从事这方面前沿研究的Denise Chen表示：“我们的研究采用的是很原始的技术。让人们害怕很简单，难的是如何让他们开心。

Hygiene products pose another problem. The researchers must find subjects who are willing to forgo deodorant for several days before each study. “That’s hard to do in this country because people are so hygiene-conscious,” Chen says. It also raises the question of whether any of this research would even matter in a real-world setting. Given all the fragrances we dab onto our bodies, any signals that sweat might contain would be undetectable.
卫生用品是第二个主要问题。研究人员必须找到实验前若干天没有使用除体味喷雾的实验对象。Chen说在美国这个讲究卫生的国家，这种人还真不好找。实验室得出的数据在真实世界是否适用也是个问题，我们每天都要往身上喷各种香水，汗液中的成分是否能够被我们察觉？

Or maybe not. Wysocki says there’s evidence that certain people can detect body odor even when masked. He tested about 40 common compounds used to cover smells and arrived at a surprising result. “It’s fairly easy to block the body odor of women in the noses of men,” he says. “But when it came to women, only two of the [masking] compounds were effective.”
不过，Wysocki的研究表明某些人可以嗅到香水和其它杂味掩盖下的体味，在实验中他使用了40多种香味物质掩盖体味，结果让他很吃惊。“女人身上只要喷了香水，男人就不太闻得到女人的体味，但是对于女人，40种物质中只有2种能够真正掩盖女人身上的体味。