According to a study conducted by Bradley Kirkman, professor of leadership at the Poole College of Management at North Carolina State University, and professors Yang Sui, Hui Wang, and Ning Li, employees will perform better under leaders who show a "moderate amount of differential treatment," Kirkman and his colleagues write in Harvard Business Review.
The study compared how 900 employees across 150 teams in three different companies in China performed under three different treatments. In the first scenario, the leaders did not engage in differential treatment and treated all members the same way, either indifferently, good, or poorly. This resulted in low team performance. In the second scenario, leaders treated employees with extreme differential treatment, resulting in the well-treated employees and poorly-treated employees erupting in conflict and characterized by poor over-all team performance. Lastly, leaders used a range of treatment; some employees didn't get much attention, others were treated moderately well and others were the favorites. The employees who received a wide range of treatment showed the highest team performance.
"The rationale here is that not all team members are created equally, and so when leaders invested more in the members who were more capable and higher performing and less in those who were not as integral to team success, team performance was maximized," they write.
While you might not be comfortable admitting you play favorites, Kirkman and his colleagues also found that most leaders in their study already played favorites without them realizing it. Differentiated treatment is a natural occurrence in the office. The trick is to keep it moderate, fair and balanced.
"As our study shows, you have to be careful not to take such treatment to the extreme or you'll end up with a dysfunctional, fractured team, and one that will be unlikely to live up to even the most modest expectations for performance," they write.