双语阅读 | 狗狗如何让青少年不再那么焦虑
How dogs make teens feel less anxious
文本难度：考研
Dogs have been a part of human society for over 20,000 years. Whereas they first served people by supporting hunters, it did not take long before they became part of the home. Companion dogs may not help secure food, but for years, evidence has mounted that they help diminish anxiety and improve sociality.
狗与人类相伴已有两万多年。最初，它们协助人类狩猎；但没过多久，便走进了千家万户。虽然作为伴侣的狗狗不再帮我们获取食物，但多年来，越来越多的证据表明，它们能有效缓解焦虑、促进社交。
Research led by Kikusui Takefumi at Azabu University in Japan, published recently in iScience, explains what might be going on. It reveals that the microbes found in the guts of dog owners are notably different from those who do not own dogs and that this is, at least partially, responsible for the behavioral differences.
日本麻布大学的菊水健史（Takefumi Kikusui）团队近期在《交叉科学》（iScience）期刊发表的一项研究，揭示了其中可能的机制：养狗者的肠道微生物组成明显异于不养狗的人，而这种差异至少在一定程度上解释了两类人行为上的不同。
The brain does not exist in isolation. The microbes found elsewhere, particularly in the gut, produce chemical compounds that influence how the brain works. Those microbes are heavily affected by diet, but are also shaped by factors like stress, pollutants, and exercise. Dr Kikusui knew from his own research that having a dog influenced the microbiota of the human gut, too. With this in mind, he wondered if microbe transfer from dogs might be helping confer psychological benefits on owners. Keen to find out, he set up an experiment with 343 participants in Tokyo.
大脑并非是孤立运作的。身体其他部位——尤其是肠道——的微生物会产生多种化学物质，从而影响大脑的运作。这些微生物深受饮食影响，同时也受到压力、污染物和运动等因素的影响。菊水博士从前期研究中得知，养狗也会改变人体肠道菌群。由此，他想到：狗狗身上的微生物是否可能通过某种方式转移给人类，并带来心理上的益处？为了验证这一猜想，他在东京开展了一项涉及343名参与者的研究。
Dr Kikusui specifically worked with teenagers. His reason for this was that adolescence is a crucial period of brain development, when social interactions often have lasting mental effects; if microbes from dogs were reducing teen anxiety and increasing teen sociality, then this would yield long-term benefits. He and his colleagues therefore psychologically analyzed 96 teens who were dog owners and 247 teens who were not. As expected, dog owners suffered from fewer social problems. More specifically, they showed reduced aggression, diminished delinquent behavior, and less social withdrawal.
菊水博士特意选择了青少年作为研究对象，因为青春期是大脑发育的关键阶段，这个时期的社交经历往往会对心理健康产生长远影响。如果来自狗狗身上的微生物真的能减轻青少年的焦虑、增强其社交能力，那么这种益处很可能会持续一生。因此，他和同事对96名养狗的青少年与247名不养狗的青少年进行了心理评估。结果正如预期：养狗的青少年在社交方面遇到的问题更少。更具体地说，他们表现出的攻击性更低，违纪行为更少，社交退缩倾向也更轻微。
Dr Kikusui and his colleagues then collected saliva samples from the participants and noted that several variants of Streptococcus and Prevotella 7 bacteria were significantly more abundant in samples from dog owners. They further found that participants in whom these key microbe variants were rare also tended to have more delinquent behaviors. This finding suggested that microbes, added to the human gut by dogs, may be influencing the brains of their owners in healthy ways.
随后，菊水博士及其同事采集了参与者的唾液样本，并发现：养狗青少年的样本中，几种链球菌（Streptococcus）和普雷沃氏菌属第7类（Prevotella 7）的变体会多得多。他们进一步观察到，那些体内缺乏这些关键微生物变体的参与者，往往有更多的违纪行为。这一发现表明，狗狗带入人类肠道的微生物，可能正以有益的方式影响着主人的大脑功能。
The ideal next step for Dr Kikusui would have been to infuse dog microbes into the bodies of non-dog-owning teens. Since that is an ethically grey area, he worked instead with mice. He cultured microbe samples from both groups of teens in the lab and fed them to 24 mice. After six weeks, he monitored them as they were put through a series of murine sociality tests, which included examinations of how long they spent sniffing unfamiliar mice and how close they would get to a distressed mouse that had previously been their cage-mate.
理想情况下，菊水博士下一步本想将狗狗相关的微生物直接移植到不养狗的青少年体内，以验证其效果。但鉴于这种做法涉及伦理争议，他转而采用小鼠进行实验。研究团队在实验室中培养了两组青少年的微生物样本，并将其喂给24只小鼠。六周后，研究人员对这些小鼠进行了一系列社交行为测试，包括观察它们花多长时间嗅探陌生小鼠，以及当曾经同笼的伙伴处于痛苦状态时，它们会主动靠近到什么程度。
Remarkably, mice carrying the microbes of teen dog owners spent up to 14 seconds sniffing unfamiliar mice, whereas mice carrying the microbes of teens without dogs spent a paltry six seconds doing so. A similar result played out with the distressed mouse test—mice with the microbes of teen dog owners often spent more than 21 seconds checking on the distressed mouse, while the other mice never spent more than three seconds doing so. Dr Kikusui admits that making direct comparisons between murine and human behavior is not ideal, but his findings nonetheless indicate that the microbiotic changes brought about by dog ownership influence the brain. If the conclusions hold, it seems that the path to a healthier mind may begin not with introspection, but with a nuzzle and a few licks.
令人惊讶的是，携带养狗青少年的微生物的小鼠，会花多达14秒的时间去嗅探陌生小鼠；而携带不养狗青少年的微生物的小鼠，这一时间仅有6秒。在有关“靠近痛苦鼠友”的测试中，也出现了类似结果：前者常常花超过21秒的时间去查看处于痛苦状态的鼠友，而后者从未超过3秒。菊水博士坦言，将小鼠行为直接与人类行为类比并不算理想，但研究结果依然清晰表明：养狗所引发的肠道菌群变化，确实会影响大脑功能。如果这些结论经得起进一步验证，那似乎可以说，通往更健康的精神状态的路，或许并非始于内省，而是始于狗狗的一次依偎和几次舔舐。
【词汇】
1. microbe n. 微生物
2. microbiota n. 微生物群
3. aggression n. 攻击性
4. delinquent adj. 违法的；不良行为的
5. saliva n. 唾液
6. infuse v. 注入；灌输
7. ethically adj. 伦理地；道德地
8. culture v. 培养（细胞或细菌）
9. paltry adj. 微不足道的；很少的
10. murine adj. 鼠类的；鼠的
11. introspection n. 内省；反省
12. nuzzle n. 用鼻子轻触；依偎
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