Chilly¹ bumps, goose pimples², goosebumps – there are a few names for when tiny elevations³ on your skin form that resemble a goose's flesh after its feathers are plucked.

冷风疹子、小疙瘩、鸡皮疙瘩--有好几个别名来形容这种情况。人的皮肤上有时候会起一些小疹子，看起来就像鸡拔掉羽毛后的样子。

And the cold, a sad tune or powerful scene from a movie can trigger this phenomenon⁴ when you least expect it.

人在遇到寒冷的时候，听到悲伤的曲调的时候，或者从电影中看到令人震撼的场景的时候，就会产生这种你最不愿看到的现象。

In this week's episode of BrainCraft, Youtuber Vanessa Hill dives into the weird⁵ and wonderful science of why humans experience the chilling sensation of goosebumps.

在本周的《大脑飞船》节目里，凡妮莎·希尔在Youtube上展示了这一怪异而又奇妙的科学，解释了为什么人会起鸡皮疙瘩的疑问。

The scientific term for this evolutionary⁶ trait is pilomotor reflex or piloerection.

科学上描述这一进化特征的专有名词是“竖毛反射”或者“立毛”。

'I want you to think of the last time you remember experiencing them,' says Hill in the YouTube clip. 'Was it at the beginning of this video? And if not, was it from the cold? Or music? A movie? Were you just having an intense emotional response to something?'

希尔在Youtube视频上说道：“我希望你们想一想最后一次起鸡皮疙瘩的情形。那是不是在视频开始的时候。如果不是，那么因为遇冷？音乐？或者电影？或者说你当时对什么东西有强烈的情绪反应？”

She continues to explain when hair standing⁷ to attention, it forms a buffer⁸ between your skin and the cold air –helping you to thermorgulate or regulate your body temperature. This is why most people tend to get goosebumps when they are cold or feel a chill.

希尔继续解释说道，当毛发竖起来的时候，在皮肤和冷空气之间形成了一道屏障--从而帮助你调节温度或者说控制体温。那也正是为什么人在冷或者感觉冷的时候会起鸡皮疙瘩。

The sensation is caused by the tiny muscles underneath⁹ each follicle, called arrector pili, and when they contract, the hair is pulled upright.

这种感觉是由每个毛囊里的细小肌肉造成的，被称之为“立毛肌”，当这些肌肉收缩时，毛发就会立起来。

'These are involuntary muscles and they're part of our sympathetic nervous system, which is responsible for most fight or flight responses,' explains Hill. 'The reaction is closely tied to our emotional state, and apart from being cold, this is why movies may be the best trigger for goosebumps.'

希尔解释说道：“这些是'不随意肌'，是我们交感神经系统的一部分，这个系统产生了大多数的应激反应。这个反应的产生和我们的情绪状态有着密切的关系，这也正是为什么除了感觉冷以外，人们最经常因为电影而起鸡皮疙瘩。”

This is because brain imaging studies have found that goosebumps activates¹⁰ structures like the amygdala and parts of the prefrontal cortex -- both found associated with pleasure and reward. And there is no rhyme or reason to when this sensation will occur, as it is sometimes brought on by a distant memory of a past event.

关于大脑成像的研究已经发现，鸡皮疙瘩能够激活人类大脑中的杏仁核神经元和部分额叶皮质--这两部分都和大脑的愉悦和激励有关。而且鸡皮疙瘩的产生没有任何规律或者理由可寻，因为有时人们会因为记忆中久远以前的一件事而起鸡皮疙瘩。

However, this phenomenon is one which descends¹¹ from our ancient ancestors who used it to keep warm and it may have even kept them alive by deterring¹² predators¹³ -- but experts have deemed this reaction useless to modern day humans.

但是，这一现象是从我们的先祖那里继承而来的，他们曾利用这一反应来保持体温。并且吓跑捕食者--不过专家们认为对于现代人类来说，这种反应毫无作用。

However, goosebumps are very important to some creatures of the world, such as cats, dogs and other mammals who use it has a way to seem larger and scarier to their predators.

然而，鸡皮疙瘩对地球上其他一些生物来说却非常重要，例如猫、狗和其他哺乳动物，它们用这一现象来使得自己看起来更大一些，从而吓跑捕食者。