That’s the main conclusion from a series of experiments conducted by Stanley and his colleagues Chris Neck, Ph.D. and Chris Neck, father-and-son researchers at Arizona State University and West Virginia University, respectively.

The findings appeared online January 6 in the Journal of Experimental Social Psychology.

For the study, Stanley recruited nearly 1,400 managers online to read about a fictional 29-year-old employee named John. The mangers all learned that John’s company was on a tight budget, and to keep costs down, had to decide how willing they would be to task John with extra hours and responsibilities without any extra pay. (Participants handing out the unpaid work in Stanley’s study were compensated $12 an hour.)

No matter how Stanley and his colleagues framed the scenario, branding John as loyal always resulted in managers being more willing to ask him to shoulder the unpaid labor.

Managers were more willing to exploit Loyal John over Disloyal John. And when a separate group of managers read a letter of recommendation about John, the letters praising John as loyal led to an increased willingness to recruit him for unpaid work over versions of John extolled for honesty or fairness.

The reverse was true, too: when John was portrayed as having a reputation to accept extra hours and workload, managers rated him as more loyal than a John who had a reputation to decline the same workload. Agreeable John and Refusal John were rated as similarly honest and fair however, demonstrating that loyalty but not closely related moral traits is bolstered by a history of doing free labor. “It’s a vicious cycle,” Stanley said. “Loyal workers tend to get picked out for exploitation. And then when they do something that's exploitative, they end up getting a boost in their reputation as a loyal worker, making them more likely to get picked out in the future.”