Please note that our focus is on the behavior of those who belong to China’s One-Child Policy (OCP) generation, not necessarily that of only child (i.e., some do have siblings though they belong to OCP generation and we didn’t control if the subjects have any siblings). Also, our result is applicable only to the behavior of being at work, not that of daily life.

https://www.fatherly.com/health-science/chinas-one-child-generation-suggests-only-children-not-selfish/