Many have experienced the rush of falling in love for the first time,

許多人都曾體驗過初次墜入愛河的悸動，

or the deep feelings of love for your children, family, and friends.

或是感受到自己對孩子、家人與朋友的深刻愛意。

But what is love from a biological perspective?

但是，以生物學觀點而言，愛是什麼？

No doubt it's intertwined with the evolutionary survival of our species.

毫無疑問地， 愛與人類的生存演化息息相關。

After all, you come from an unbroken line of organisms reproducing from the very first microbe that split in two,

畢竟，你來自一個堅不可摧的生物繁衍流程：從最初的微生物一分裂為二、

to your ancestors who have all successfully mated since the dawn of time.

到從宇宙之初至今所有成功配對繁衍的祖先。

Sadly, if you fail to have children, this perfect streak comes to a halt.

可惜的是，你如果沒有生小孩，這完美的生命線就會愕然中止。

But while we're driven to reproduce, we're also driven to make sure our offspring survive.

就如同我們都有繁衍的本能，我們也有確保後代存活的動力。

Though we often associate love with the heart, the true magic can be seen inside the brain.

雖然我們常把愛與心聯想在一起，真正的魔法卻可能發生在大腦之中。

It may not be entirely surprising to find out that the brain of somebody in love looks awfully similar to one on cocaine.

你可能不會感到意外，戀愛中人的大腦看起來跟吸食古柯鹼者的大腦非常相似。

Cocaine acts on the pleasure centers in the brain by lowering the threshold at which they fire.

古柯鹼透過降低大腦快樂中樞生效的門檻，進而對它起作用。

This means that you feel really good a lot easier.

這表示你會更容易地感覺良好。

We see the same thing in the brains of those in love, but it's not just the cocaine or the love that makes you feel good.

我們在戀愛中人的大腦裡也看到同樣現象，但讓你心情好的不僅是古柯鹼或是愛。

It's the fact that anything you experience will now more easily set off pleasure centers and make you feel good.

事實是，你在這個時期經歷的任何事都更容易刺激快樂中樞並讓你有好心情。

Because of this, you not only fall in love with the person, but begin to build a romanticized view of the world around you.

正因如此，你不只是愛上那個人，更會開始用浪漫的視角檢視世界。

Interestingly, nearby pain and aversion centers begin to fire less, so you become less bothered by things.

有趣的是，鄰近的痛苦和厭惡中樞作用的次數也開始降低，所以你也較不容易為事所擾。

Simply put, we love being in love.

簡單來說，我們熱愛戀愛的感覺。

So what chemicals are at work to make all this happen?

那到底是哪些化學物質促成這一切的發生呢？

Both during orgasm or by simply looking at photos of a loved one, there is a surge of dopamine and norepinephrine from the ventral tegmental area.

無論是高潮期間，或單純看著所愛之人的照片，我們中腦腹側被蓋區內的多巴胺和正腎上腺素都會急遽上升。

This not only triggers sexual arousal and your racing heart, but gives you the motivation, craving, and desire to be with a person more and more.

這不只會誘發性興奮和心跳加速，還會給你更多與某人相處的動機、渴求和慾望。

You see, romantic love is not simply an emotion; it's a drive from the motor of the mind.

這麼說吧，浪漫的愛情不單只是情感，它更是從心靈深處驅動的動力。

And this motor brings about intense energy, focused attention, and elation.

而這股動力也帶來豐沛的精力、集中的注意力和歡欣之情。

The pleasure centers are part of the brain's reward system: the mesolimbic dopamine system.

快樂中樞是大腦獎賞機制的一部分：中腦多巴胺系統。

If you stimulate this region while learning, learning becomes much easier because it's pleasurable and perceived as a reward.

如果你在學習時刺激這個區域，學習將變得更簡單，因為它讓人享受並被視為獎勵。

We also see a surge in the neuromodulator, oxytocin from the nucleus accumbens, sometimes called the "commitment neuromodulator" because, in mammals, it helps to reinforce bonding or attachment.

我們也會看到伏隔核中調節神經的「催產素」（也被稱為「愛情荷爾蒙」）大量增加，因為它在哺乳類動物中的作用是強化愛和羈絆。

When prairie voles are injected with either oxytocin or vasopressin, they will instantly find a mate to pair bond with.

當草園田鼠被注射催產素或血管加壓素時，牠們會立刻展開求偶活動。

Finally, studies have shown that people in love have low levels of serotonin, which is similar to people with obsessive-compulsive disorder.

最後，研究顯示，戀愛中人含有較低的血清素，這一點和強迫症患者類似。

This is likely the cause of our obsession and infatuation during early love.

這很可能是引起戀愛初期意亂情迷的原因。

Amazingly, these areas associated with intense romantic love can remain active for decades.

神奇的是，這些與強烈浪漫愛情有關的區域可以維持活躍長達數十年。

And while there are many other physiological and psychological components that add to the mix,

而雖然過程中還有許多生理和心理上的組成元素，

the truth is, science still knows very little about exactly why or how love works.

但事實是，目前科學還是很難解釋「愛」的作用原因或方法。

And yet somehow, we all seem to know it when we feel it.

然而，我們似乎總能知道我們感受到愛的時刻。

Got a burning question you want answered?

有你迫切想知道答案的問題嗎？

Ask it in the comments, or on Facebook and Twitter.

在影片下方或 Facebook 和 Twitter 留言詢問我們吧！

And subscribe for more weekly science videos.

記得訂閱頻道，以觀看更多每週更新的科學影片。