"Hedonic treadmill" refers to the tendency to always go back to the same level of happiness despite positive life events. Personal happiness does seem to increase as family incomes rise, a phenomenon apparent in both the U.S. and Britain. But once we reach a modest level of income, more money doesn't bring greater satisfaction. This is when we find ourselves on what experts call the "hedonic treadmill".

“快乐水车”指尽管经历了本该令人快乐的事情，人们却并没有变得更快乐的现象。随着家庭收入的增长，个体的幸福感会增强，这种现象在美国和英国很常见。但是一旦人们的收入达到了一定水平，收入的增加却不能再带来更多的快乐。这时，人们就陷入了“快乐水车”时期。

Social scientists explain this happiness plateau through the "aspiration adjustment hypothesis." As soon as we acquire a moderate amount of wealth, our expectations rise for a higher quality of life. When we don't reach these new levels, our spirits flag, leaving us disillusioned.

社会学家用“期望调适假说”来解释这种高原现象。一旦我们获得了一定的财富之后，对于生活品质的期望值便会增加。如果不能达到这些新的高度，我们就会一蹶不振，感到幻想破灭。

A second explanation comes from the idea of "relative position": We compare our wealth and place in the social hierarchy to those around us. No matter how high we climb, we almost always encounter someone who is richer or who has more things.

我们还可以从“相对位置”这一概念中找到解释。我们往往会将自己的财富和社会地位与身边的人进行比较。不管我们在成功的路上爬得有多高，我们几乎总是可以碰到比自己更富有或拥有更多的人。