Scientists are usually reluctant to attribute humanlike feelings to animals. But it's generally accepted that many animals have moods, including fish.

科学家们通常不愿意把人类的情感归因于动物。但人们普遍认为许多动物都有情绪，包括鱼。

The new study shows that fish can detect fear in other fish, and then become afraid too – and that this ability is regulated by oxytocin, the same brain chemical that underlies the capacity for empathy in humans.

新的研究表明，鱼可以察觉到其他鱼的恐惧，然后也变得害怕——这种能力是由催产素调节的，这种大脑化学物质也是人类同理心的基础。

The researchers demonstrated this by deleting genes linked to producing and absorbing oxytocin in the brains of zebrafish, a small tropical fish often used for research. Those fish were then essentially antisocial – they failed to detect or change their behavior when other fish were anxious.

研究人员通过删除斑马鱼大脑中与产生和吸收催产素相关的基因来证明这一点，斑马鱼是一种经常用于研究的小型热带鱼。这些鱼本质上是反社会的——当其他鱼焦虑时，它们无法发现或改变自己的行为。

But when some of the altered fish received oxytocin injections, their ability to sense and mirror the feelings of other fish was restored — what scientists call "emotional contagion."

但当一些鱼接受催产素注射后，它们感知和反映其他鱼感受的能力得到了恢复——科学家们称之为“情绪感染”。

They respond to other individuals being frightened. In that regard, they behave just like us, said University of Calgary neuroscientist Ibukun Akinrinade, a co-author of the study.

“它们对其他鱼受到的惊吓做出了反应。在这方面，它们的行为就像我们一样。”该研究的合著者、卡尔加里大学神经科学家伊布昆·阿基里纳德说。

The study also showed that zebrafish will pay more attention to fish that have previously been stressed out – a behavior the researchers likened to consoling them.

这项研究还表明，斑马鱼会更加关注以前压力很大的鱼——研究人员将这种行为比作安慰。

Previous research has shown that oxytocin plays a similar role in transmitting fear in mice.

先前的研究表明，催产素在小鼠体内传递恐惧时起着类似的作用。

The new research illustrates "the ancestral role" of oxytocin in transmitting emotion, said Rui Oliveira, a behavioral biologist at Portugal's Gulbenkian Institute of Science and a study co-author.

葡萄牙古尔本基安科学研究所的行为生物学家、该研究的合著者瑞·奥利维拉说，这项新研究阐明了催产素在传递情感方面的“祖传性”。

This brain processing "may have already been in place around 450 million years ago, when you and me and these little fish last had a common ancestor," explained Hofmann.

霍夫曼解释说，这种大脑处理“可能在大约4.5亿年前就已经存在了，那时你、我和这些小鱼还拥有着共同的祖先。”

Oxytocin is sometimes thought of as a "love" hormone, but Hofmann said it's actually more like "a thermostat that determines what is socially salient in a particular situation – activating neural circuits that may make you run from danger, or engage in courtship behavior."

催产素有时被认为是一种“爱情”荷尔蒙，但霍夫曼说，它实际上更像是“一个恒温调节器，决定着在特定情况下、在社交方面什么是最重要的——激活也许会使你逃离危险或从事求爱行为的神经回路”。