First, they explain that if a given variable is playing a role in affecting wellbeing then we should expect any change in that variable to correlate with the observed changes in wellbeing.

首先，他们解释说，如果一个给定的变量在影响幸福感方面发挥了作用，那么我们应该预期该变量的任何变化都与所观察到的幸福感变化相关。