This is the greatest mystery of our adult life: How can we spend all day typing at a computer and go home feeling exhausted?

This question actually lies very close to a hotly contested issue in psychology: What causes mental fatigue? Why is desk work so depleting?

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

But scientists do have some clues. 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.

A study last August tracked 100 nurses in the U.K. 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. Result: There was no correlation between the amount of physical work the nurses did and their feelings of fatigue.

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.

“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,” Inzlicht said. Temptations make us less motivated to do our work, which, in turn, may make us tired.

“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.

“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.

Words to Learn 相关词汇

【疲劳】píláo fatigue weariness or exhaustion from labor, exertion, or stress

【诱惑】yòuhuò temptation something tempting

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”？

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

“说实话，这个问题还是个谜团，”多伦多大学主要研究自我控制、动机和疲劳的心理学家迈克•因茨里希特说。

但科学家确实找到了一些线索。

当我们完成任务时，我们努力集中精神完成任务，或者最终彻底失去兴趣。我们缺乏足够动力完成这项任务。我们很容易被想做的其他事情吸引（例如：刷社交媒体或读音乐博客），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。

去年8月的一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。他们的体力活动量可以通过设备监控跟踪。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。结果发现：护士的体力劳动量与疲劳感之间没有关联。

相反，他们发现了另一组数据之间有微弱的相关性：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。这些感受可能提高了他们的工作积极性，从而可能让他们觉得自己精力旺盛。

“如果你正在打字工作，像我一样开了几个浏览器窗口。我们被各种诱惑包围，”因茨里希特说。诱惑使我们没有足够的动力完成工作，而且可能会让我们感到疲倦。

“作为一个有机生物，我们需要达到多个目标才能生存，”因茨里希特解释说。我们不仅仅需要寻找食物或者追求生活中的激情。我们需要同时达成这些众多的 目标才能健康、活得好。“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，别干那个，去干点别的。’”他认为，这种机制就是疲惫感。

(Chinadaily.com.cn)