> We value people who are loyal. We think about them in positive terms. They get awarded often. It's not just the negative side

If the managers also award loyal workers in various ways, it would hardly be exploitative. As a manager, if something absolutely needs to get done outside of normal work hours, of course I would lean towards asking the person most likely to say yes. And of course I would also give that person a larger end-of-year salary increase, bonus, or fast-tracked promotion to recognize their efforts and commitment. It seems odd for the study to focus purely on the additional work the loyal workers are doing, and ignore the various ways in which they would be rewarded for it.