In a new study of flexible work policies, researchers at the University of Washington Foster School of Business have found that people who elect to work an early shift are perceived by their bosses to be better employees than those who work a later shift.

The study, co-authored by Foster School doctoral student Kai Chi (Sam) Yam and assistant professors of management Ryan Fehrand Christopher Barnes, is the first to document such a bias in the modern workplace.

"In three separate studies, we found evidence of a natural morning bias at work," says Yam. "Compared to people who choose to work earlier in the day, people who choose to work later in the day are implicitly assumed to be less conscientious and less effective in their jobs."

Today, nearly 80 percent of American businesses offer some kind of non-traditional work schedule. These include compressed work weeks, job shares and, most frequently, flextime—a policy allowing employees to begin and end their work day within a range of acceptable hours.

Such schedules have proven to be popular with employees. Flextime makes it easier to meet family and other non-work commitments. It also accommodates an employee's personal work style.

And because employees love the programs, firms are learning to love them, too. Research shows that flexible work practices generally lead to increased productivity, higher job satisfaction and decreased turnover intentions.

Yet a serious question lurks beneath this trend toward scheduling latitude: Do employees who take advantage of flexible work policies incur career penalties for doing so?

Yam, Fehr and Barnes designed three studies to test for managerial bias in flextime situations.

The first established that, on average, people make a greater natural implicit—that is, non-conscious—association between the concepts of "morning" and "conscientiousness" than between the concepts of "evening" and "conscientiousness."

A field study explored the impact of this bias in actual work settings and on ratings provided by real supervisors. Even after statistically controlling for total work hours, employees who started work earlier in the day were rated by their supervisors as more conscientious, and thus received higher performance ratings.

A final laboratory experiment confirmed the bias. Participants acting the part of supervisors were asked to rate fictitious employees whose performance was identical—the only difference was their work schedule. The acting managers perceived the employees who worked from 7 a.m. to 3 p.m. to be more conscientious and higher performing than their counterparts who worked from 11 a.m. to 7 p.m.

The findings suggest that some employees are experiencing a deduction in their performance ratings that is not based on anything having to do with actual performance. This could lead to less frequent pay raises and promotions.

Yam suggests that senior managers should educate supervisors to make them aware of their tendency to stereotype night owls as less productive than early birds. And they should implement performance ratings based on objective standards that do not allow implicit prejudices—such as a morning bias—to color their assessments.

And for flextime-loving employees? Yam acknowledges that workers might be better served when using flextime by moving their schedules earlier rather than later in the day. But rather than give in to the morning bias, he suggests that employees raise the subject of hours and timing with their supervisors to make explicit the understanding that start time is immaterial.

"One way or another, team leaders must come to accept that the people who use flextime to start their day late are not necessarily lazier than their early-bird colleagues," Yam says. "Otherwise, flextime policies that might serve both employees and employers well will become known, and avoided, as routes to dead-end careers."

"Morning employees are better employees: Employees' start times influence supervisor performance ratings" is forthcoming in the Journal of Applied Psychology.