上班不过坐着动动手指，为什么还是这么累？

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?

成年人的生活里最大的谜团之一：明明我们只是在电脑上打一天字，回家后怎么就“累成狗”？不过是对着屏幕动动手指，怎么能这么累，累到只想瘫在沙发上？

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?

这个问题实际上非常接近心理学中一个比较有争议的问题：什么导致心理疲劳？办公室工作何以让人如此疲劳？

"It is kind of a mystery, to be honest," said Michael Inzlicht, a University of Toronto psychologist who studies self-control, motivation, and fatigue.

“说实话，这个问题差不多还是个谜团，”多伦多大学主要研究自我控制、动机和疲劳的心理学家Michael Inzlicht称。

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.

但科学家确实找到了一些线索。为什么在没有进行任何体力劳动时，我们还会因为工作而感到疲倦？以下是关于这个问题的一种假设，让我们来看看吧。

Hypothesis: we get so tired because our motivation runs out

假设：我们感到疲倦是因为动力不足

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.

当我们完成任务时，我们很难专注于任务本身，最终彻底失去兴趣。我们没有足够的动力去完成这项任务。我们很容易被我们想做的事情所吸引（例如：刷社交媒体或阅读音乐博客），而不是专注于我们必须做的事情。而这种矛盾可能会导致疲劳。

In August, researchers in the UK published new evidence that finds some indirect evidence for the motivational model.

去年8月，英国的研究人员发表了新的结论，他们找到了动机模型的间接证据。

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.

这项研究跟踪了英国的100名护士的两次12小时轮班。在整个轮班期间，护士们需要定时报告他们的疲劳程度。并且，他们的体力活动量可以通过设备被监控跟踪到。当研究人员在研究什么可能解释疲劳时，他们有一些有趣的发现。

Here's the topline result: There was no correlation between the amount of physical work the nurses did and their feelings of fatigue.

结果发现：护士做的体力劳动量与疲劳感之间没有相关性。

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，他们发现了另一组之间具有小的相关性：疲惫感最低的护士对工作的控制感最强，获得的回报感也最强。这些感受可能增加了他们的工作动力，从而可能提高了他们对自身能量的感知。

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也从他的工作中发现了符合动机模型的证据。几年前，他和加拿大卡尔顿大学心理学家Marina Milyavskaya一起进行了研究。他们监测了加拿大麦吉尔大学的159名学生，为期一周。

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.

整个星期，参与者都在不停地通过短信回答各种问题，包括他们此刻面临的诱惑是什么、渴望什么和在努力地自我控制什么，以及他们是否觉得自己筋疲力尽。

"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.

“令我们惊讶的是，最大预测因素不是是否进行了自我控制，”Inzlicht说。相反，预测因素是他们感受到的诱惑数量。

"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，像我一样你打开了几个浏览器。我们被各种诱惑包围着，"他说。各种诱惑使我们没有足够的动力完成工作，反过来，这可能会让我们感到疲倦。

And there may be an evolutionary reason for why our brains would do this.

我们的大脑为什么会这样做可能是因为进化方面的原因。

"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.

“作为一个有机生物，我们需要达到多个目标才能生存，”Inzlicht解释道。我们不仅仅需要寻找食物或者追求生活中的激情。我们需要做很多事情才能健康、繁荣。

"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.

“因为多个目标相互竞争占用我们的时间，而我们需要一个机制来发出信号，'嘿，停止做那件事，去干点别的。'”他认为，这种机制可能会让我们感到疲惫。

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.

从这个角度来看，提高我们继续完成任务的动力可能会使我们觉得不那么疲惫。研究发现，在人们很累的时候，只要向他们支付一些钱，他们就可以完成任务。在关于身体耐力的研究中也发现了类似的结果：人们其实很容易被激励去完成超出他们认为的身体极限的工作。