Today, tomorrow, learn English naturally. 天天自然学英语
Tears without Fears: Sniffing Women’s Tears Reduces Aggression in Men
All land mammals have tear glands in their eyes, but, until recently, the human tearing experience was considered unique. After all, humans are the only animals to shed tears while watching Beaches. Now a new Weizmann Institute of Science study reveals that human tears have much more in common with those of other animals than previously thought: Just as with the tears of mice and blind mole rats, they contain chemicals that reduce aggression in others. The study, published today in PLOS Biology, showed that sniffing women’s tears lowered brain activity related to aggression in men, reducing aggressive behavior.
The study addressed the long-standing mystery of why we cry. Charles Darwin was puzzled by emotional tearing, which appeared to have no useful function – beyond the role that tears play in lubricating the eye – so he concluded that such tearing must have evolved in humans by chance. However, numerous studies since then, particularly in rodents, have shown that mammalian tears contain chemicals serving as social signals that can be emitted on demand.
One of the most common purposes of these tears is to reduce aggression. The tear liquid of female mice contains chemicals that affect aggression networks in the brain, thereby reducing fighting among male mice. Similarly, subordinate male blind mole rats smear themselves in tears to reduce the aggressive behavior they face from dominant males.
Prof. Noam Sobel, whose lab in Weizmann’s Brain Sciences Department studies olfaction, the sense of smell, has hypothesized that human tears also contain chemicals that serve as social signals. In 2011, his team showed in research published in Science that sniffing women’s emotional tears reduced testosterone levels in men, resulting in somewhat diminished levels of sexual arousal.
In the new study, researchers, led by PhD student Shani Agron from Sobel’s lab, set out to determine whether tears have the same aggression-blocking effect in people as they do in rodents. In a series of experiments, men were exposed to either women’s emotional tears or saline, without knowing what they were sniffing or being able to distinguish between the two. Next, they played a two-person game designed to elicit aggressive behavior in one player toward the other, who was portrayed to be cheating. When given the opportunity, the men could get revenge on the perceived cheaters by causing them to lose money, though they themselves gained nothing. After the men sniffed women’s emotional tears, their revenge-seeking aggressive behavior during the game dropped by about 44% – or nearly in half.
This seemed equivalent to the effect observed in rodents, but rodents have a structure in their noses called the vomeronasal organ that picks up social chemical signals. Since humans don’t have this organ, researchers wanted to know how they were able to sense the social chemicals. To find an answer, the researchers applied the tears to 62 human olfactory receptors in a laboratory dish and found that four of these receptors were activated by the tears, even though tears are odorless.
The researchers repeated the experiments while examining the men’s brains in an MRI scanner. Functional imaging showed that two aggression-related brain regions – the prefrontal cortex and the anterior insula – were less active when the men were sniffing the tears. The greater the difference in this brain activity between saline and tears, the less often the player took revenge during the game.
“We’ve shown that tears activate olfactory receptors and that they alter aggression-related brain circuits, significantly reducing aggressive behavior,” Sobel says. “These findings suggest that tears are a chemical blanket offering protection against aggression – and that this effect is common to rodents and humans, and perhaps to other mammals as well.”– Prof. Noam Sobel, Weizmann’s Brain Sciences Department
In fact, recent studies have found that dogs also shed emotional tears. However, more research is needed to determine whether these tears contain chemical signals that can be picked up by other dogs or by humans.
As for social interactions among humans, future research will explore whether the new study’s findings also apply to women. “When we looked for volunteers who could donate tears, we found mostly women, because for them it’s much more socially acceptable to cry,” Agron says. “We knew that sniffing tears lowers testosterone, and that lowering testosterone has a greater effect on aggression in men than in women, so we began by studying the impact of tears on men because this gave us higher chances of seeing an effect. Now, however, we must extend this research to include women to obtain a fuller picture of this impact.”
Agron adds that this effect is likely to gain in importance when verbal communication is impossible, as with babies: “Infants can’t talk, so for them relying on chemical signals to protect themselves against aggression can be critical.”
注释：
mole: n
表示" 鼹鼠；钱鼠"，如：A mole has burrowed a hole in the sand. 鼹鼠在沙地上挖了一个洞。
lubricate: v
表示"润滑; 加润滑剂"，means "make smooth and able to move or be moved easily"，如：My throat needs lubricating. 我需要润润嗓子了。If you never bother to lubricate your engine, of course it will seize up. 如果你老是怕麻烦，不给发动机添加润滑油，发动机当然会失灵卡住啦。
smear: v
表示"涂抹；弄脏；诽谤"，如：We smeared cream on our faces. 我们在脸上搽雪花膏。My opponent tried to smear my reputation . 我的对手竟想诋毁我的名声。
testosterone: n
表示" 睾丸激素"，如：Testosterone levels normally surge during the middle of a pregnancy. 睾丸激素的水平通常在一个怀孕的中期汹涌上扬。
saline: adj
表示"含盐的；咸的"，如：Chains of saline lakes are found in places in continental interiors. 在大陆内部的某些地区发现了盐湖系列。
elicit: v
表示" 引出；诱出"，means " draw out (facts, a response, etc.) from sb"，如：The detectives tried to elicit where he had hidden his loot. 侦探试图诱使他说出他藏匿赃物的地方。
vomeronasal: adj
表示"[医] 犁[骨]鼻骨的"，如：Vomeronasal organ is their main sense of smell organ. 其中梨鼻器是它们主要的嗅觉器官。
olfactory: adj
表示" 嗅觉的"，如：It arouses their olfactory sense. 这唤起了他们的嗅觉。
cortex: n
表示" 外皮；（大脑）皮层"，如：However, the cortex is not without purpose in pain processing. 然而，皮层在疼痛处理过程中并非无目的性。
中文简要说明：
所有陆地哺乳动物都拥有泪腺，以色列魏兹曼科学研究院（Weizmann Institute of Science）的一项新研究显示出，人类的眼泪中也含有能减少他人攻击性的化学物质，最神奇的是明明没有味道，但是嗅闻女性的眼泪却能够降低男性大脑与攻击相关区域的活动，进而减少攻击行为，这项新研究刚发表在《PLOS Biology》上。
据兹曼科学研究院官方报导，众多研究表明哺乳动物的眼泪中含有作为社交信号的化学物质，可以根据需要发出，特别是啮齿动物而人类也是。
这些眼泪的最常见目的之一是减少攻击性。母老鼠的泪液中含有能影响大脑中攻击网络的化学物质，从而减少雄性老鼠之间的打斗。同样地，被压制的雄性盲鼹鼠会用泪液涂抹自己，以减少正在攻击牠的雄性盲鼹鼠的攻击行为。
魏兹曼的脑科学系的索贝尔教授（Noam Sobel）他的实验室研究嗅觉，也提出了人类的眼泪可能也含有作为社交信号的化学物质的假设。
2011年，他的团队在《科学》（Science）期刊上发表的研究中表明，嗅闻女性的眼泪会降低男性的睪固酮水平，从而使性兴奋水平稍微降低。
在后续的研究中，由索贝尔实验室的博士生阿格朗（Shani Agron）领导的研究团队，想暸解人类的眼泪是否跟啮齿动物相同的减少攻击效果。在一系列实验中，受试验男性暴露于女性眼泪和一般的食盐水，受试者不知道他们正在嗅的是哪一种，也无法区分两者。
接下来，他们参与了可以互相攻击或者报复的2人电玩游戏，在有机会的情况下，这些男性可以向对手进行攻击或报复，使对方失去金钱，而他们自己却没有获得任何好处。在嗅闻女性的情感性泪液后，他们在游戏中寻求报复的攻击性行为降低了约44%差不多一半。
这似乎相当于在啮齿动物中观察到的效果，啮齿动物有一种称为蝶鼻器官的结构，能够捕捉社交化学信号。但是人类没有这个器官，研究人员想知道受试者是怎么感受到的，为找到答案，研究人员将泪液应用于实验室培养皿中的62个人类嗅觉受器，发现其中有4个受器对眼泪产反应，尽管泪液是无味的。
研究人员在检查男性大脑的同时重复了实验，使用MRI扫描后与嗅闻盐水相比，当男性去闻眼泪时，2个与攻击有关的大脑区域，前额皮质和前脑岛的活动都有减少。
留言微信公众号《自然学英语LearnNaturally》，可咨询更多！