Moody people are often baffling to those of us with steadier emotions.
喜怒無(wú)常的人常常令情緒穩(wěn)定的人感到困惑。

But scientists argue that changing moods – as seen in sulking teenagers, grumpy spouses, or bad-tempered parents - serve an important purpose.
但科學(xué)家認(rèn)為情緒多變——多見(jiàn)于陰郁的青少年，愛(ài)發(fā)牢騷的配偶，或者暴脾氣的父母——其實(shí)有它的重要目的。

Rather than being a weakness, they are nature's way to of helping us adapt to an ever changing world. So when times are good and spirits are high, we take more risks at a time they are likely to be rewarded.
這不是缺點(diǎn)，而是幫助我們適應(yīng)瞬息萬(wàn)變的世界的自然方式。

And when times are tough, sulking can help us conserve our energy.
當(dāng)萬(wàn)事順意、志得意滿(mǎn)時(shí)，我們更傾向于去冒風(fēng)險(xiǎn)，因?yàn)槲覀冇X(jué)得自己很可能會(huì)得到回報(bào)。當(dāng)時(shí)局艱難時(shí)，陰郁的情緒可以幫我們保存能量。

To take a human example, a stock market trader who makes a successful deal becomes more optimistic about the outcome of his next transaction.
舉人類(lèi)為例，股市交易者大賺一筆時(shí)，他對(duì)下一筆交易將會(huì)信心滿(mǎn)滿(mǎn)。

He is then likely to take more risks – as he becomes more optimistic things will go in his or her favour.
他會(huì)傾向于冒更多險(xiǎn)，因?yàn)樗麡?lè)觀(guān)地期待事情會(huì)順?biāo)煨囊狻?/p>

The increase in risk taking allows him to make maximum gains at a time when risk taking is most likely to pay off.
在風(fēng)險(xiǎn)投資回報(bào)率高時(shí)，冒更大風(fēng)險(xiǎn)讓他可以獲得最大化的利益。

This holds true when a variety of different events have an underlying connection, the authors argue.
作者論證說(shuō)，當(dāng)多個(gè)不同事件之間存在潛在聯(lián)系時(shí)，這個(gè)結(jié)果是成立的。

To take an example from the natural world, the authors suggest an animal's mood improves on finding a number of fruits in a tree.
作者又舉了一個(gè)自然界的例子，他指出動(dòng)物在一株樹(shù)上發(fā)現(xiàn)許多果實(shí)時(shí)情緒會(huì)改善。

Rather than assessing each tree individually, this good mood helps the animal to look at the big picture – and optimistically make it think fruits are in abundance.
情緒大好的動(dòng)物不會(huì)挨個(gè)打量每株樹(shù)，而是會(huì)樂(lè)觀(guān)地認(rèn)為這一片樹(shù)的果實(shí)都很豐碩。

This encourages the animal to climb up the neighbouring branch – where good conditions make it more likely that there will be a tasty fruit available.
這會(huì)鼓勵(lì)它爬上旁邊那棵樹(shù)，由于這片樹(shù)生長(zhǎng)環(huán)境良好，所以那顆樹(shù)的枝頭上很可能掛著一個(gè)好吃的果子。

It may be increased rainfall or sunshine has caused fruit to become more abundant, the authors suggest.
作者指出，也許是降雨和日照增多讓果實(shí)更豐饒。

'In this situation, it makes little sense to update expectations for each tree independently,' the authors write, and makes the animal expect 'a general increase in reward and update expectations for all related trees accordingly.'
作者寫(xiě)道：“在這種情況下，動(dòng)物不會(huì)對(duì)每棵樹(shù)都抱有不同的期望，而是會(huì)整體地期待‘周邊的樹(shù)都能有更多回報(bào)’?！?/p>

Eran Eldar, of University College London said: 'This effect of mood should be useful whenever different sources of reward are interconnected or possess an underlying momentum.
英國(guó)倫敦大學(xué)學(xué)院伊然·艾爾達(dá)說(shuō)：“當(dāng)不同回報(bào)的來(lái)源相互間都有聯(lián)系或擁有潛在動(dòng)力，這種情緒效應(yīng)將會(huì)很有用。

'That may often be the case in the natural as well as in the modern world, as successes in acquiring skills, material resources, social status, and even mating partners may all affect one another.'
“不僅在自然界，在現(xiàn)代社會(huì)，獲取技能的成功與獲得物質(zhì)資源、社會(huì)地位，甚至和找對(duì)象都是環(huán)環(huán)相扣的?！?/p>

When rewards are starting to thin out – for example if winter is coming – then a negative mood will result in an individual event, such as finding a fruit, being 'downgraded'– allowing behaviour and expectations to be quickly adjusted downwards.
當(dāng)回報(bào)減少——比如冬天來(lái)臨——消極的情緒就會(huì)致使動(dòng)物對(duì)找到果實(shí)的期望降低，從而調(diào)整自己的行為。

The authors suggest that this could lead to behaviours such as an animal deciding to save energy and hibernate instead of rushing around.
作者說(shuō)，這會(huì)導(dǎo)致動(dòng)物決定節(jié)省體力或冬眠，而不是到處亂跑。

英文來(lái)源：每日郵報(bào)
譯者：劉傳坤
審校&編輯：丹妮