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If you've ever played Marco Polo,
如果你玩过马可波罗这个游戏，
you know that it can be pretty tricky to locate sounds with your eyes closed.
你就会知道闭着眼睛定位声音很难。
But assuming you don't swim violently into a wall trying to tag someone,
但是如果方法得当，
you can do it.
你做得到的。
Your brain can figure out the difference between what each of your ears is hearing
大脑可以分辨出每只耳朵听到内容的差别
and use that to tell where a sound is coming from.
以此分辨声音从哪里来。
But how do we do it,
但是我们怎么做呢，
and what would happen if our right ear suddenly switched places with the left?
如果我们的右耳突然和左耳交换一下位置会发生什么事呢？
This might seem like a silly question,
这个问题看起来很傻，
but it's actually one that people study with a device called a pseudophone.
但实际上，人们用一种叫做“假声器”的设备来研究这个问题。
The pseudophone was invented in the 1920s,
假声器发明于20世纪20年代，
and it makes it seem like a sound is coming from somewhere that it's not.
通过它，声音像是来自某个其它地方的声音。
It's basically a couple of old-school ear trumpets with sound-proof tubing attached to them.
从根本上说，它就是一对带有隔音管的旧式助听器。
The user puts an ear trumpet on either side of their head,
使用者在头两边各放一个助听筒，
and then runs the tubing from each trumpet to their other ear.
然后声音从每一个喇叭上沿着导管传至另一只耳朵。
More modern pseudophones electronically flip-flop the sound going to each ear in a pair of headphones,
更现代的假声器以电子方式通过耳机将声音传到耳朵，
but… just savor that ear trumpet image for a second.
但是…只要想一下那个助听器的样子。
Generally, humans can adapt to most things—
一般来说，人类可以适应大多数事物—
like when you suddenly step into bright sunlight,
就像你突然接触耀眼的阳光，
or when you get used to loud music at a concert.
或者习惯了音乐会上喧闹的乐曲。
But one thing we can't seem to adapt to is switching around our ears.
但有一件事我们似乎无法适应，那就是转动耳朵。
This one researcher in the '20s, I kid you not,
我不骗你，20年代的研究员，
wandered the streets of Berlin for more than 80 hours while wearing a pseudophone.
戴着假声器在柏林街头游荡了80多个小时。
He was trying to see if he could become habituated to it
他正在试着看自己是否能适应，
and train his brain to flip-flop the sounds back to normal. Turns out he couldn't.
并训练大脑把声音恢复到正常，事实证明是不行的。
With his eyes closed, he still pointed in the wrong direction when he heard sounds.
他闭着眼睛听着声音仍指错了方向。
If anything, all that practice made him better at pointing to exactly 180 degrees
如果有什么成果的话，所有这些练习使他更擅长指向反方，
opposite from where the sound was actually coming from.
这与声音的真正来源截然相反。
All of this suggested to researchers that there really is something important about
研究表明，
how and when each of our ears encounters a sound
我们的耳朵是如何及何时遇到声音真的很重要
that allows us to tell where it's coming from.
这种声音可以帮助我们分辨出声音的来源。
See, under normal circumstances, we're actually really good at localizing sound.
正常情况下，实际上我们很擅长定位声音。
We can determine the angle that a sound is coming from within one to two degrees.
我们可以确定声音在1~2度之间准确的角度。
We do it through a process called binaural sound localization,
此次定位通过一个叫做双耳声音定位的程序来完成，
which means exactly what it sounds like:
双耳声音定位指的就是：
We use both ears to pinpoint a sound's location.
我们用两只耳朵来定位声音。
We locate sound horizontally using the difference in intensity between what each ear is hearing
根据每只耳朵听到声音强度的差别
and the tiny time delay between when one ear hears it and when the other one does.
以及它们之间的细微延迟来确定声音的发出位置。
So, for example, if headphones played a sound in both your ears at the same time,
例如，如果听筒同时在耳朵里播放声音，
your brain would do the math and conclude that the sound was happening inside your head.
大脑会进行数学运算，并得出结论：声音正在你的头脑中发生。
To do the same thing vertically,
纵向地做同样的事
we use the flappy external parts of our ears, which are called pinnae or auricles.
耳朵外部有绒毛，我们称之为外耳。
The different shapes and contours of our auricles at different angles make sounds sound different.
外耳的不同形状以及不同角度的轮廓使得声音听起来会有所不同。
Auricles also help us sort out the location of stuff that's in the cone of confusion—
外耳也帮助我们在锥形干扰区准确找出物体的位置
and, yes, that is totally a technical term.
是的，锥形干扰区完全是一个技术术语,
It's the region in front of and behind you where sound generally reaches each ear at the same time.
它是你前方和后方区域，通常在这个区域内声音到达每只耳朵的时间是一致的。
With hearing, it's generally accepted that
有了听觉，人们普遍认为，
we don't really build out a map of 3D space on the eardrum or anything like that.
我们并没有在耳膜或类似的东西上建立三维地图。
Instead, it's really all about your brain constantly doing these calculations,
相反，一切都是大脑不断计算出来的，
most of which are done in a region called the superior olivary complex in the brain stem.
其中大部分是在脑干中称为上橄榄核复合体区域完成的。
Except… that's probably not the whole story, either.
除了…这可能也不是全部。
For one, there’s a lot of evidence that moving the head
首先，很多证据表明移动头部
and body changes our ability to figure out where sounds are coming from, too.
和身体也会改变我们辨别声音来源的能力。
A 1980 pseudophone study and a 2018 blindfold study found that
1980年的假声器研究和2018年的蒙眼研究发现，
people were better at localizing sounds when they could move their head and walk around—
当人们晃动头部并四处走动时，他们更擅长定位声音。
although moving their head made them worse at it when they were wearing the pseudophone.
尽管戴着假声器时，头部晃动的效果更差。
This kind of hearing—where we think about
这种听觉值得我们思考
a sound's location in relation to ourselves— is called egocentric hearing.
声音的位置与我们自身的关系，我们称之为以自我为中心的听觉。
And a 2017 study from PLOS Biology suggested that
2017年，PLOS生物学研究表明，
there might be a difference between it and so-called allocentric hearing,
以自我为中心的听觉和所谓的集中听觉之间或许会有所不同，
where we think about a sound's location more objectively.
集中听觉会让我们更客观地思考声音的位置。
It's kind of the difference between thinking about your buzzing phone as being "on your left" or "over there on the table."
这是把嗡嗡作响的手机想象成“在你的左边”或“在桌子那边”的区别。
When the researchers recorded ferret brains,
当研究人员记录雪貂的大脑时发现，
they found that some cells fired differently when the ferrets turned their heads to reflect the fact that
雪貂转头时，一些细胞发出的声音与它们发出的声音不同，
the sound was now coming from somewhere else in relation to them.
这些现象反映出声音现在来自其它相关的地方。
But other neurons didn't change how they fired.
但其他神经元并没有改变发射方式。
This suggests that, if we're anything like ferrets,
这表明，如果我们是雪貂，
we maybe do build out some sort of audio map of the world after all.
或许我们确实建立了世界的某种音频地图。
Studies have also shown that our sense of sight can also play a role in how we process where sound is coming from.
研究还表明，视觉也在我们处理声音来源的过程中发挥着作用。
And for people who are blind,
对于盲人来说，
it's possible to use sound to build out a kind of map the way most seeing people do with sight.
使用声音构建一种地图是可能的，就像大多数人有视觉一样。
Other weird things can affect our sense of sound, too.
其他奇怪的东西也会影响我们的听觉。
There are a couple of studies that suggest that for evolutionary reasons,
其它研究表明，出于进化的原因，
"looming" sounds—you know,
你知道，“隐隐约约”的声音，
like when something big and loud is approaching you— are perceived differently.
人们对这种隐隐约约声音（就像某个巨大响亮的东西靠近你一样）的感知不同。
We're likely to overestimate the intensity of sounds that are getting closer to us.
我们可能会过高估计渐近声音的强度。
And there's actually a different pattern of neural activity for sounds that are getting closer
实际上，渐近声音的神经活动模式是不同的
as opposed to those that are moving away.
这与渐远声音截然不同。
From a survival standpoint, that makes sense.
从生存的角度来看，这是有道理的。
But regardless, as always when it comes to our brains,
但不管怎样，就像人类大脑一样，
things are more complicated than they appear.
事情比表面看起来要复杂得多。
Except how silly people must've looked with an old-fashioned pseudophone on their head.
除了人们头上戴着旧式假声器看起来真傻。
That seems pretty straightforward. Thanks for watching this episode of SciShow Psych!
这似乎非常简单。感谢收看本期的心理科学秀！
If you'd like to keep learning about the brain with us,
如果您想继续了解大脑，
you can go to youtube.com/scishowpsych and subscribe.
可以访问并订阅youtube.com/scishowpsych。
