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If you've ever seen the cartoon Pinky and the Brain, you already know that bigger brains are way better.
如果你看过动画片《两只老鼠打天下》，你就会知道大脑越大越好。
And if only those scientists had made that mouse's brain just a little bigger,
如果科学家们能让老鼠的大脑再大一点，
maybe he could have actually taken over the world.
也许老鼠真的可以统治世界。
But, it turns out the cartoon lied to us. Shocking, I know.
但事实证明，动画片欺骗了我们，有点震惊，我知道。
In real life, things are much more complicated, and size isn't everything — or even much, really, when it comes to intelligence.
现实生活中要复杂得多，头脑大小并不能决定一个人的智力水平——真的。
It might be tempting to think that brain size is really important because it's one of the things that makes us stand out.
人们可能很容易认为，头脑大小真的很重要，因为它是让我们脱颖而出的原因之一。
Relative to our bodies, our brains are bigger than the brains of other primates.
相对于我们的身体，比起其它灵长类动物，人脑要大一些。
And they've been getting bigger over time— our ancient relative Homo habilis had a brain one-third the size of ours, for example.
随着时间的推移，人脑会越来越大——例如，我们远古近亲能人的大脑只有我们的三分之一大。
So you'd think that among people, those of us with the biggest brains would also be the smartest.
所以你可能会认为，有着最大大脑的人类也是最聪明的。
But… while it's true our species has evolved larger brains over the past two million years or so…
但是，在过去200万年左右的时间里，人类的大脑确实进化的大了些……
that growth stopped around when we developed stone tools.
在我们发明石器工具后大脑就停止了增长。
And since then, our brains have actually been shrinking.
从那以后，实际上我们的大脑一直在萎缩。
In the last 20,000 years, our brains have shrunk by 10% — that's almost the size of a baseball, which is a lot of brain to lose.
在过去的20,000年里，我们的大脑萎缩了10%——几乎相当于一个棒球的大小，这是一个很大的脑损失。
And...I mean… if size was everything, that would mean we're a lot dumber now.
我是说，如果头脑大小决定智力，那就意味着我们现在笨多了。
We're not, though… Right? And that actually makes sense when you look at much more recent research on brains and intelligence.
但我们不笨，对吧？当你看到更多关于大脑和智力的最新研究时，这个说法其实是有道理的。
In the past half-century or so, lots of psychologists and neuroscientists have tried to draw connections between brain size
在过去半个世纪左右的时间里，许多心理学家和神经科学家都试图在大脑大小（通常是体积或重量）
— usually volume or weight— and intelligence, as measured by IQ tests or other standardized exams.
和智力（通过智商测试或其他标准化考试来衡量）之间找寻联系。
And they just haven't found a solid relationship.
只是还没有找到稳固的联系。
For example, a 2015 meta-analysis combined the results of 88 studies on over 8,000 brains,
例如，2015年的一项分析综合了基于8000多个大脑的88项研究结果，
and found that size only accounted for a little less than 6% of the variation in IQ between people.
研究人员发现，头脑大小在人与人之间的智商差异中只占不到6%。
They also found that earlier studies published higher correlation between brain size and IQ.
他们还发现，早期研究公布了头脑大小和智商存在着较高相关性的结果。
Which either means that the connection between intellect and size has been disappearing over time…
也就是说，随着时间的推移，智力和头脑大小之间的联系正在消失……
or that earlier studies were biased against publishing negative results.
或者早期研究对公布的负面结果存有偏见。
Regardless, scientists just can't seem to agree that size really matters.
无论如何，科学家似乎不能同意大脑大小真的很重要。
And slowly but surely, other factors have been emerging.
但肯定的是，慢慢地其他因素也显现出来。
New research suggests size is less important than connectedness, for example.
例如，一项新的研究表明，头脑的连通性比大小更重要。
And not how you might expect, because having highly connected neurons doesn't make you smarter.
不是你期望的那样，因为高度连接的神经元并不会让你更聪明。
Instead, less is more.
相反，低度连接的神经元会让你更聪明。
This connectedness can be measured by looking at what scientists call arborization in the brain.
这种连接可以通过观察科学家们所谓的大脑分支来衡量。
That's the number and shape of dendrites– the long spindly branches neurons use to connect to other neurons
即树突的数量和形状，树突是神经元连接其他神经元的细长分支
— which scientists can estimate using neurite orientation dispersion and density imaging, cutely abbreviated to NODDI.
——科学家们可以用神经突定向色散和密度成像来估计树突，简写为NODDI。
It might seem pretty natural to assume that people with tons and tons of dendrites would have an advantage
我们通常会假设拥有大量树突的人在智力上有优势。
— more neuronal connections, more computational power, right?
——神经元连接更多，计算能力更多，对吧?
But… when scientists examined the brains of 259 participants in a 2017 study, they found the opposite.
但是，当科学家在2017年的一项研究中检测了259名参与者的大脑时，结果正好相反。
There was a weak but significant negative correlation between the number of dendrites and test scores.
树突数目与测试成绩呈弱而显著的负相关关系。
And that suggests efficiency is better than quantity
这表明效率胜于数量
— which isn't as surprising as you might think, if you think about it this way:
——这没你想的那么惊讶，如果你这样想：
Imagine your friend just moved and you're trying to find your way to their new place.
假设你的朋友刚搬了家，你正试图找到他们的新家。
If there are like a million roads you could take to get there, it'll take you forever to find the right one,
如果你要走一百万条路才能到达目的地，那么你永远都找不到那条路，
and you'll waste time and effort on wrong turns.
你会在错误的转弯上浪费时间和精力。
But if there's just one direct route right to their door, you'd be there in a jiffy.
但如果只有一条直接路线可以直接到达门口，你马上就会到达。
The same seems to hold true for neurons.
神经元似乎也是如此。
The fewer dendrite branches there are, the easier a time the brain has firing the right sequence of neurons.
树突分支越少，大脑正确的神经元序列越容易被激活。
And ultimately, that means quicker, more efficient thinking.
最终，思考更快，效率更高。
But when it comes to wiring, simplicity isn't the only key.
但说到布线，简单并不是唯一的关键因素。
To stick with that house-finding analogy:
再次以找房子打个比方：
it's easier to get to a place that happens to be in your neighborhood instead of two towns over.
去你家附近比在两个城镇来回穿梭要容易得多。
There's just less of a chance you'll get lost if the journey is short.
如果旅程很短，你迷路的机会就更少了。
In your brain, those neighborhoods are created by wrinkles on the surface,
在你的大脑中，这些区域是由表面的皱褶，
which are known as gyri and sulci — gyri being the mounded bits, and sulci being the gaps.
我们称之为脑回和脑沟，脑回是堆积位，脑沟是间隙。
Those wrinkles are there so we can fit more brain inside our skulls,
所以我们可以把更多的大脑皱着塞进颅骨，
kind of like how crunching up a piece of paper allows it to fit into a smaller container.
就像把一张纸揉成一团可以放进更小的容器一样。
And conveniently, these folds let neurons with similar functions group closer together.
这些皱褶让功能相似的神经元更紧密地聚集在一起。
Instead of having to stretch connections all the way across a flat surface,
神经元可以不必在平面上伸展连接，
neurons can more easily talk with neighbors that are squashed up in the same or a nearby gyrus.
而更容易地与被压扁的邻元素或附近的脑回联系，
And there is evidence that variations in the shape of sulci and gyri are associated with general cognitive ability in humans.
有证据表明，脑沟和脑回形状的变化与人类的一般认知能力有关。
A 2016 study published in Current Biology looked at the brains and cognitive abilities of 440 adults and 662 children.
2016年发表在《当代生物学》杂志上的一篇研究调查了440名成年人和662名儿童的大脑和认知能力。
High resolution structural imaging was used to calculate the local gyrification index, or LGI — a measurement of the extremeness of brain folding.
高分辨率结构成像——一种测量大脑褶皱极度的方法被用于计算局部旋回指数。
When compared to participants' performances on tests designed to probe cognitive ability, the researchers found that in both adults and children,
与受试者测试认知能力时的表现相比，研究人员发现，无论是成人还是儿童，
more extreme levels of folding were associated with better scores.
褶皱程度越高，得分越高。
In fact, the structure of the folds predicted about 12% of the variance in cognitive abilities in one of their samples.
事实上，褶皱的结构预测了其中一个样本中认知能力差异的12%左右。
The researchers responsible for the study suggested that this may be largely because of folding in areas of the brain that are multimodal
负责这项研究的研究人员认为，这可能主要是由于大脑多模态区域褶皱
— ones where a lot of functions are performed in a small area.
——小范围内执行多功能造成的。
More folding could make those areas better able to communicate and process information by putting important neurons closer together.
更多的褶皱可以使这些区域重要的神经元连接更紧密，从而更好地交流和处理信息。
But... even when we take into account brain wrinkles and things like dendrite arborization,
但是…即使我们考虑到大脑褶皱和树突分枝，
there's still a lot of variation in intelligence that isn't well explained.
智力仍然存在很多差异，但这些差异并没有得到很好的解释。
One thing is for sure, though — size is only a tiny piece of the puzzle.
但有一件事是肯定的——头脑大小只是我们困惑的一小部分。
Luckily, there are plenty of other aspects of our brains that scientists can investigate to figure out what makes us so clever.
幸运的是，科学家们还可以研究我们大脑的很多其他方面，来弄清楚是什么让我们如此聪明。
Thanks for watching this episode of SciShow Psych!
感谢收看心理科学秀节目。
If you want to learn more about your brain and how it works, stick around!
如果你想了解更多关于你的大脑及其工作原理，接着收看我们的节目哦！
This channel is all about exploring the science of the mind.
这个频道是关于心理的。
And you can get new episodes sent straight to your youtube subscription feed by clicking that subscribe button!
你可以通过点击订阅按钮将新剧集直接发送到你的youtube订阅的节目上!
