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If you've ever seen the cartoon Pinky and the Brain, you already know that bigger brains are way better.
如果你看過動畫片《兩只老鼠打天下》，你就會知道大腦越大越好。
And if only those scientists had made that mouse's brain just a little bigger,
如果科學家們能讓老鼠的大腦再大一點，
maybe he could have actually taken over the world.
也許老鼠真的可以統治世界。
But, it turns out the cartoon lied to us. Shocking, I know.
但事實證明，動畫片欺騙了我們，有點震驚，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.
現實生活中要復雜得多，頭腦大小并不能決定一個人的智力水平——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.
人們可能很容易認為，頭腦大小真的很重要，因為它是讓我們脫穎而出的原因之一。
Relative to our bodies, our brains are bigger than the brains of other primates.
相對于我們的身體，比起其它靈長類動物，人腦要大一些。
And they've been getting bigger over time— our ancient relative Homo habilis had a brain one-third the size of ours, for example.
隨著時間的推移，人腦會越來越大——例如，我們遠古近親能人的大腦只有我們的三分之一大。
So you'd think that among people, those of us with the biggest brains would also be the smartest.
所以你可能會認為，有著最大大腦的人類也是最聰明的。
But… while it's true our species has evolved larger brains over the past two million years or so…
但是，在過去200萬年左右的時間里，人類的大腦確實進化的大了些……
that growth stopped around when we developed stone tools.
在我們發明石器工具后大腦就停止了增長。
And since then, our brains have actually been shrinking.
從那以后，實際上我們的大腦一直在萎縮。
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.
在過去的20,000年里，我們的大腦萎縮了10%——幾乎相當于一個棒球的大小，這是一個很大的腦損失。
And...I mean… if size was everything, that would mean we're a lot dumber now.
我是說，如果頭腦大小決定智力，那就意味著我們現在笨多了。
We're not, though… Right? And that actually makes sense when you look at much more recent research on brains and intelligence.
但我們不笨，對吧？當你看到更多關于大腦和智力的最新研究時，這個說法其實是有道理的。
In the past half-century or so, lots of psychologists and neuroscientists have tried to draw connections between brain size
在過去半個世紀左右的時間里，許多心理學家和神經科學家都試圖在大腦大?。ㄍǔＪ求w積或重量）
— usually volume or weight— and intelligence, as measured by IQ tests or other standardized exams.
和智力（通過智商測試或其他標準化考試來衡量）之間找尋聯系。
And they just haven't found a solid relationship.
只是還沒有找到穩固的聯系。
For example, a 2015 meta-analysis combined the results of 88 studies on over 8,000 brains,
例如，2015年的一項分析綜合了基于8000多個大腦的88項研究結果，
and found that size only accounted for a little less than 6% of the variation in IQ between people.
研究人員發現，頭腦大小在人與人之間的智商差異中只占不到6%。
They also found that earlier studies published higher correlation between brain size and IQ.
他們還發現，早期研究公布了頭腦大小和智商存在著較高相關性的結果。
Which either means that the connection between intellect and size has been disappearing over time…
也就是說，隨著時間的推移，智力和頭腦大小之間的聯系正在消失……
or that earlier studies were biased against publishing negative results.
或者早期研究對公布的負面結果存有偏見。
Regardless, scientists just can't seem to agree that size really matters.
無論如何，科學家似乎不能同意大腦大小真的很重要。
And slowly but surely, other factors have been emerging.
但肯定的是，慢慢地其他因素也顯現出來。
New research suggests size is less important than connectedness, for example.
例如，一項新的研究表明，頭腦的連通性比大小更重要。
And not how you might expect, because having highly connected neurons doesn't make you smarter.
不是你期望的那樣，因為高度連接的神經元并不會讓你更聰明。
Instead, less is more.
相反，低度連接的神經元會讓你更聰明。
This connectedness can be measured by looking at what scientists call arborization in the brain.
這種連接可以通過觀察科學家們所謂的大腦分支來衡量。
That's the number and shape of dendrites– the long spindly branches neurons use to connect to other neurons
即樹突的數量和形狀，樹突是神經元連接其他神經元的細長分支
— which scientists can estimate using neurite orientation dispersion and density imaging, cutely abbreviated to NODDI.
——科學家們可以用神經突定向色散和密度成像來估計樹突，簡寫為NODDI。
It might seem pretty natural to assume that people with tons and tons of dendrites would have an advantage
我們通常會假設擁有大量樹突的人在智力上有優勢。
— more neuronal connections, more computational power, right?
——神經元連接更多，計算能力更多，對吧?
But… when scientists examined the brains of 259 participants in a 2017 study, they found the opposite.
但是，當科學家在2017年的一項研究中檢測了259名參與者的大腦時，結果正好相反。
There was a weak but significant negative correlation between the number of dendrites and test scores.
樹突數目與測試成績呈弱而顯著的負相關關系。
And that suggests efficiency is better than quantity
這表明效率勝于數量
— which isn't as surprising as you might think, if you think about it this way:
——這沒你想的那么驚訝，如果你這樣想：
Imagine your friend just moved and you're trying to find your way to their new place.
假設你的朋友剛搬了家，你正試圖找到他們的新家。
If there are like a million roads you could take to get there, it'll take you forever to find the right one,
如果你要走一百萬條路才能到達目的地，那么你永遠都找不到那條路，
and you'll waste time and effort on wrong turns.
你會在錯誤的轉彎上浪費時間和精力。
But if there's just one direct route right to their door, you'd be there in a jiffy.
但如果只有一條直接路線可以直接到達門口，你馬上就會到達。
The same seems to hold true for neurons.
神經元似乎也是如此。
The fewer dendrite branches there are, the easier a time the brain has firing the right sequence of neurons.
樹突分支越少，大腦正確的神經元序列越容易被激活。
And ultimately, that means quicker, more efficient thinking.
最終，思考更快，效率更高。
But when it comes to wiring, simplicity isn't the only key.
但說到布線，簡單并不是唯一的關鍵因素。
To stick with that house-finding analogy:
再次以找房子打個比方：
it's easier to get to a place that happens to be in your neighborhood instead of two towns over.
去你家附近比在兩個城鎮來回穿梭要容易得多。
There's just less of a chance you'll get lost if the journey is short.
如果旅程很短，你迷路的機會就更少了。
In your brain, those neighborhoods are created by wrinkles on the surface,
在你的大腦中，這些區域是由表面的皺褶，
which are known as gyri and sulci — gyri being the mounded bits, and sulci being the gaps.
我們稱之為腦回和腦溝，腦回是堆積位，腦溝是間隙。
Those wrinkles are there so we can fit more brain inside our skulls,
所以我們可以把更多的大腦皺著塞進顱骨，
kind of like how crunching up a piece of paper allows it to fit into a smaller container.
就像把一張紙揉成一團可以放進更小的容器一樣。
And conveniently, these folds let neurons with similar functions group closer together.
這些皺褶讓功能相似的神經元更緊密地聚集在一起。
Instead of having to stretch connections all the way across a flat surface,
神經元可以不必在平面上伸展連接，
neurons can more easily talk with neighbors that are squashed up in the same or a nearby gyrus.
而更容易地與被壓扁的鄰元素或附近的腦回聯系，
And there is evidence that variations in the shape of sulci and gyri are associated with general cognitive ability in humans.
有證據表明，腦溝和腦回形狀的變化與人類的一般認知能力有關。
A 2016 study published in Current Biology looked at the brains and cognitive abilities of 440 adults and 662 children.
2016年發表在《當代生物學》雜志上的一篇研究調查了440名成年人和662名兒童的大腦和認知能力。
High resolution structural imaging was used to calculate the local gyrification index, or LGI — a measurement of the extremeness of brain folding.
高分辨率結構成像——一種測量大腦褶皺極度的方法被用于計算局部旋回指數。
When compared to participants' performances on tests designed to probe cognitive ability, the researchers found that in both adults and children,
與受試者測試認知能力時的表現相比，研究人員發現，無論是成人還是兒童，
more extreme levels of folding were associated with better scores.
褶皺程度越高，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.
事實上，褶皺的結構預測了其中一個樣本中認知能力差異的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
負責這項研究的研究人員認為，這可能主要是由于大腦多模態區域褶皺
— ones where a lot of functions are performed in a small area.
——小范圍內執行多功能造成的。
More folding could make those areas better able to communicate and process information by putting important neurons closer together.
更多的褶皺可以使這些區域重要的神經元連接更緊密，從而更好地交流和處理信息。
But... even when we take into account brain wrinkles and things like dendrite arborization,
但是…即使我們考慮到大腦褶皺和樹突分枝，
there's still a lot of variation in intelligence that isn't well explained.
智力仍然存在很多差異，但這些差異并沒有得到很好的解釋。
One thing is for sure, though — size is only a tiny piece of the puzzle.
但有一件事是肯定的——頭腦大小只是我們困惑的一小部分。
Luckily, there are plenty of other aspects of our brains that scientists can investigate to figure out what makes us so clever.
幸運的是，科學家們還可以研究我們大腦的很多其他方面，來弄清楚是什么讓我們如此聰明。
Thanks for watching this episode of SciShow Psych!
感謝收看心理科學秀節目。
If you want to learn more about your brain and how it works, stick around!
如果你想了解更多關于你的大腦及其工作原理，接著收看我們的節目哦！
This channel is all about exploring the science of the mind.
這個頻道是關于心理的。
And you can get new episodes sent straight to your youtube subscription feed by clicking that subscribe button!
你可以通過點擊訂閱按鈕將新劇集直接發送到你的youtube訂閱的節目上!
