上班不過坐着動動手指，爲什麼還是這麼累？

This is the greatest mystery of our adult life: How can we spend all day typing at a computer and go home feeling exhausted? How could merely activating the small muscles of our fingers leave us craving the couch at the end of the day?
成年人的生活裏最大的謎團之一：明明我們只是在電腦上打一天字，回家後怎麼就“累成狗”？不過是對着屏幕動動手指，怎麼能這麼累，累到只想癱在沙發上？

This question actually lies very close to one of the more hotly contested issues in psychology: What causes mental fatigue? Why is desk work so depleting?
這個問題實際上非常接近心理學中一個比較有爭議的問題：什麼導致心理疲勞？辦公室工作何以讓人如此疲勞？

"It is kind of a mystery, to be honest," said Michael Inzlicht, a University of Toronto psychologist who studies self-control, motivation, and fatigue.
“說實話，這個問題差不多還是個謎團，”多倫多大學主要研究自我控制、動機和疲勞的心理學家Michael Inzlicht稱。

But scientists do have some clues. There is a hypothesis for why we get so tired from work when we're not physically active. Let's dive in.
但科學家確實找到了一些線索。爲什麼在沒有進行任何體力勞動時，我們還會因爲工作而感到疲倦？以下是關於這個問題的一種假設，讓我們來看看吧。

Hypothesis: we get so tired because our motivation runs out
假設：我們感到疲倦是因爲動力不足

As we work on a task, we struggle to focus on it or eventually lose interest in it. We become less motivated to do the task. We become drawn to the things we want to do (scrolling social media or reading music blogs, for instance), rather than the things we have to do. And this tension possibly causes fatigue.
當我們完成任務時，我們很難專注於任務本身，最終徹底失去興趣。我們沒有足夠的動力去完成這項任務。我們很容易被我們想做的事情所吸引（例如：刷社交媒體或閱讀音樂博客），而不是專注於我們必須做的事情。而這種矛盾可能會導致疲勞。

In August, researchers in the UK published new evidence that finds some indirect evidence for the motivational model.
去年8月，英國的研究人員發表了新的結論，他們找到了動機模型的間接證據。

This study tracked 100 nurses in the UK over two 12-hour shifts. Throughout the shifts, the nurses reported how fatigued they felt at regular intervals. They also wore devices that monitored and tracked the amount of physical activity they were engaged in. When the researchers investigated what could possibly explain the fatigue, they found some interesting patterns.
這項研究跟蹤了英國的100名護士的兩次12小時輪班。在整個輪班期間，護士們需要定時報告他們的疲勞程度。並且，他們的體力活動量可以通過設備被監控跟蹤到。當研究人員在研究什麼可能解釋疲勞時，他們有一些有趣的發現。

Here's the topline result: There was no correlation between the amount of physical work the nurses did and their feelings of fatigue.
結果發現：護士做的體力勞動量與疲勞感之間沒有相關性。

Instead, they found this small correlation: The nurses who were least likely to feel fatigued from their work also felt the most in control of their work, and the most rewarded for it. These feelings may have boosted their motivation, which may have boosted their perception of having energy.
相反，他們發現了另一組之間具有小的相關性：疲憊感最低的護士對工作的控制感最強，獲得的回報感也最強。這些感受可能增加了他們的工作動力，從而可能提高了他們對自身能量的感知。

Inzlicht has also found evidence for the motivational model in his work. A few years ago, he and Carleton University psychologist Marina Milyavskaya monitored 159 students at McGill University in Canada for a week.
Inzlicht也從他的工作中發現了符合動機模型的證據。幾年前，他和加拿大卡爾頓大學心理學家Marina Milyavskaya一起進行了研究。他們監測了加拿大麥吉爾大學的159名學生，爲期一週。

Throughout the week, the participants were peppered with text message questions about what temptations, desires, and effortful self-control they were engaging in at the moment, and whether they felt drained.
整個星期，參與者都在不停地通過短信回答各種問題，包括他們此刻面臨的誘惑是什麼、渴望什麼和在努力地自我控制什麼，以及他們是否覺得自己筋疲力盡。

"What was surprising to us was the biggest predictor [of fatigue] was not whether they had exerted self-control," Inzlicht said. Instead, the predictor was the number of temptations they felt.
“令我們驚訝的是，最大預測因素不是是否進行了自我控制，”Inzlicht說。相反，預測因素是他們感受到的誘惑數量。

"If you're typing at work, and if you're anything like me, you got a few browsers open. These lead us down these rabbit holes that lead to temptations," he said. Temptations make us less motivated to do our work, which, in turn, may make us tired.
"如果你正在打字工作，像我一樣你打開了幾個瀏覽器。我們被各種誘惑包圍着，"他說。各種誘惑使我們沒有足夠的動力完成工作，反過來，這可能會讓我們感到疲倦。

And there may be an evolutionary reason for why our brains would do this.
我們的大腦爲什麼會這樣做可能是因爲進化方面的原因。

"As an organism, we need to meet multiple goals to survive," Inzlicht explains. We're not solely focused on finding food or pursuing our passions in life. We need to do all these things to be a healthy, thriving species.

“作爲一個有機生物，我們需要達到多個目標才能生存，”Inzlicht解釋道。我們不僅僅需要尋找食物或者追求生活中的激情。我們需要做很多事情才能健康、繁榮。

"Because these multiple goals compete with one another [for our time], we need a mechanism in place that signals, 'Hey, stop doing that thing and do something else.'" That mechanism, he suggests, could be fatigue.
“因爲多個目標相互競爭佔用我們的時間，而我們需要一個機制來發出信號，'嘿，停止做那件事，去幹點別的。'”他認爲，這種機制可能會讓我們感到疲憊。

In this light, boosting our motivation to stay on a task could lead us to feel less fatigued. One study found that just paying people some money when they're depleted can keep them on task. A similar thing is found in studies on physical endurance: People can be easily pushed to work beyond what they think is their physical limit.
從這個角度來看，提高我們繼續完成任務的動力可能會使我們覺得不那麼疲憊。研究發現，在人們很累的時候，只要向他們支付一些錢，他們就可以完成任務。在關於身體耐力的研究中也發現了類似的結果：人們其實很容易被激勵去完成超出他們認爲的身體極限的工作。