It’s a natural inclination to place people in a category. It helps us process information to make it easy to remember or interact with them, according to an article in The Wall Street Journal. In the workplace, managers put employees into one of three boxes: people who perform well (A players), those who perform poorly (C players), and those who are stuck in the middle (B players).

“But the inclination to put people into boxes and leave them there can do a lot of harm — to managers, to the employees and to the companies they work for,” says the article’s author Peter Capelli, the George W. Taylor professor of management and director of the Center for Human Resources at the Wharton School.

Broad categories miss a lot of subtleties, so people’s true talents and strengths often get ignored. They also make it hard to recognize when people improve or stumble in their performance.

“What’s more, our prophecies become self-fulfilling — we give people we see as stars more opportunities to succeed, while denying those chances to those we expect to fail,” Capelli says.

So, how can you and your managers be more fair? Capelli offers these approaches.

1. Respond to an employee’s performance more frequently and quickly, reflecting how variable that performance actually is. This might mean a bonus based on a project, rather than a year-end bonus.

2. Rethink how you assign people to certain projects. For instance, monitor their performance and take them out if they slip — and slot in people whose performance is surging.

3. Create new performance categories based on the actual tasks that people have to perform. For instance, evaluate based on things such as negotiating agreements or managing projects.

4. Be more active in how you manage employees. Set expectations and hold people accountable for performance and provide feedback.

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