How do animals experience pain? - Robyn J. Crook

譯者: Winston Szeto 審譯者: Helen Chang

Humans know the surprising prick of a needle,

人類知道被針扎的那種驚人刺痛

the searing pain of a stubbed toe and the throbbing of a toothache.

腳趾踢到東西的劇痛

牙疼的抽痛

We can identify many types of pain and have multiple ways of treating it.

我們能識別許多類型的疼痛 並有多種治療方法

But what about other species?

其他物種又如何？

How do the animals all around us experience pain?

我們周遭的動物怎樣感知痛楚？

It’s important that we find out.

我們很需要明白

We keep animals as pets, they enrich our environment,

動物作為我們的好伴侶

給我們的環境增添生氣

we farm many species for food,

作為我們的食物

and we use them in experiments to advance science and human health.

也被用於實驗，推進人類健康科學發展

Animals are clearly important to us,

動物顯然對我們很重要

so it’s equally important that we avoid causing them unnecessary pain.

所以避免對牠們造成 不必要的痛楚同樣重要

For animals that are similar to us, like mammals,

跟人類相似的哺乳類動物

it's often obvious when they're hurting.

牠們感到痛楚往往顯而易見

But there's a lot that isn't obvious,

但有很多並不容易察覺

like whether pain relievers that work on us also help them.

像是對我們有效的止痛方法 對牠們有效嗎？

And the more different an animal is from us,

一個物種愈是跟人類不同

the harder it is to understand their experience.

愈難理解牠們的感知

How do you tell whether a shrimp is in pain?

怎樣知道一隻蝦感到痛楚？

A snake?

一條蛇呢？

A snail?

一隻蝸牛呢？

In vertebrates— including humans— pain can be split into two distinct processes.

在人類等脊椎生物

痛楚可分為兩個過程

In the first, nerves in the skin sense something harmful

首先神經和皮膚感覺到傷害

and communicate that information to the spinal cord.

把有關訊息傳送到脊髓

There, motor neurons activate movements that make us rapidly jerk away

脊髓的運動神經元刺激身體運動

使我們快速避開威脅

from the threat.

This is the physical recognition of harm called nociception.

這種物理上辨識傷害的能力 就是「痛覺」

And nearly all animals, even those with very simple nervous systems,

幾乎所有物種

甚至神經系統簡單的物種

experience it.

都有「痛覺」

Without this ability, animals would be unable to avoid harm

沒有痛覺，就沒有避痛的能力

and their survival would be threatened.

生存也會受到威脅

The second part is the conscious recognition of harm.

另一過程就是意識上辨識傷害的能力

In humans, this occurs when the sensory neurons in our skin

在人類，這過程涉及 皮膚的感覺神經元

make a second round of connections via the spinal cord to the brain.

透過脊椎向大腦傳送第二輪訊息

There, millions of neurons in multiple regions create the sensations of pain.

各區域數以百萬計神經元製造痛楚感覺

For us, this is a very complex experience associated with emotions

意識上辨識傷害過程複雜，關係到恐懼

like fear, panic and stress, which we can communicate to others.

焦急

壓力等等

可在人際間傳遞的情感

But it’s harder to know exactly how animals experience

但其他物種怎樣體會同樣過程

this part the process,

則較難理解

because most of them can’t show us what they feel.

因為牠們大都不能 對我們表達自己的感受

However, we get clues from observing how animals behave.

但我們可從觀察動物行為得到線索

Wild, hurt animals are known to nurse their wounds,

野生動物受傷後會舔傷口

make noises to show their distress, and become reclusive.

會咆哮抒發壓力

也會離群獨處

in the lab, scientists have discovered that animals like chickens and rats

科學實驗也證明雞和老鼠

will self-administer pain-reducing drugs if they’re hurting.

在受傷時給自己餵食止痛藥

Animals also avoid situations where they’ve been hurt before,

動物也會迴避讓牠們受過傷害的環境

which suggests awareness of threats.

種種行為都證明動物能意識到威脅

We’ve reached the point that research has made us so sure

多項研究已充分說服我們

that vertebrates recognize pain

脊椎動物能辨識痛楚

that it’s illegal in many countries to needlessly harm these animals.

在很多國家非必要地 傷害脊椎動物是違法的

But what about other types of animals, like invertebrates?

至於無脊椎動物等其他動物又如何？

These animals aren't legally protected,

牠們未有法律保障

partly because their behaviors are harder to read.

原因之一是牠們的行為較難解讀

We can make good guesses about some of them, like oysters, worms and jellyfish.

但當中部分物種的行為較易揣度

例如牡蠣

蠕蟲

以及水母

These are examples of animals that either lack a brain

這類動物不是缺乏大腦

or have a very simple one.

就是腦袋結構簡單

So an oyster may recoil when squirted with lemon juice, for instance,

牡蠣被滴上檸檬汁後縮起

because of nociception.

是痛感的反應

But with such a simple nervous system,

但牠們因為神經系統簡單

it’s unlikely to experience the conscious part of pain.

理應沒有意識上辨識痛楚的能力

Other invertebrate animals are more complicated, though.

其他無脊椎動物則較複雜

Like the octopus, which has a sophisticated brain

例如八爪魚

牠們腦袋精密

and is thought to be one of the most intelligent invertebrate animals.

是少數高智商無脊椎動物之一

Yet in many countries, people continue the practice of eating live octopus.

但生吃八爪魚在很多國家仍常見

We also boil live crayfish, shrimp, and crabs,

小龍蝦、蝦和蟹也會被活活以水煮熟

even though we don't really know how they're affected either.

即使牠們箇中感覺如何仍未可知

This poses an ethical problem,

這正是道德問題所在

because we may be causing these animals unnecessary suffering.

我們可能對牠們造成不必要傷害

Scientific experimentation, though controversial,

較具爭議性的科學實驗 提供了一些線索

gives us some clues.

Tests on hermit crabs show that they’ll leave an undesirable shell

寄居蟹在實驗中被電擊後

if they’re zapped with electricity.

就會離開欠理想的外殼

But stay if it’s a good shell.

但會留在理想的外殼

And octopi that might originally curl up an injured arm to protect it,

八爪魚捲起受傷的爪以作保護

will risk using it to catch prey.

但要捕食時卻冒險用上

That suggests that these animals make value judgments around sensory input,

種種事實顯示 無脊椎動物能作意識判斷

instead of just reacting reflexively to harm.

對傷害並非只作反射反應

Meanwhile, crabs have been known to repeatedly rub a spot on their bodies

此外，蟹會在被電擊後

where they’ve received an electric shock.

不停搔被電擊部位

And even sea slugs flinch when they know they’re about to receive

海蛞蝓預知預知自己快被騷擾時

a noxious stimulus.

也會立刻閃避

That means they have some memory of physical sensations.

這意謂著無脊椎動物 是有物理感知記憶力

We still have a lot to learn about animal pain.

關於動物痛楚課題，有待進一步研究

As our knowledge grows, it may one day allow us to live in a world

隨著有關知識累積

也許有一天我們會生活在 不會非必要地引發痛苦的世界裡

where we don’t cause pain needlessly.