The rule of thumb for managers is to set actionable goals with specific expectations for their teamsYou might ask for 10 new clients by the end of the month, or five business development ideas by the end of the week. That's how you get concrete results, right?

New evidence shows that that may not be the case. When setting goals for your team, you may not actually want to be too specific.

Steve Martin, director of business training firm Influence at Work, writes that "single-number" goals can demotivate your employees.

In a Harvard Business Review article, Martin explains that there are two factors that contribute to whether or not a person is motivated to achieve a goal: challenge and attainability. You need to strike a balance by setting a goal that won't seem  unattainable to employees and dishearten them, but that is challenging enough to give them a sense of accomplishment when they reach it.

When you set a specific goal of 10 new clients, that often has a negative impact on the challenge-attainability balance. On the other hand, if you ask for 8-10 new clients, what Martin calls "high-low goals," that tends to give space for both challenge and attainability.

A recent study by Florida State University tested a group of people looking to lose weight. Half of them were assigned a goal of losing 2 pounds per week, while the other half were tasked with losing 1-3 pounds per week. Only half of those assigned the single-number goal were motivated enough to enroll in an additional 10-week weight-loss program, compared with 80 percent of the high-low goal group. The high-low group also lost an extra half pound per week on average.

"Given that one of the challenges that managers and leaders face is to promote sustained efforts toward the organizational and operational goals they set, this research suggests they may be able to obtain substantially greater success by bracketing the goals they set with high and low levels of achievement," Martin writes.

The one caveat Martin notes is that high-low marks don't usually work as well when setting entirely new goals. The technique works better with a recurring goal, such as with a business development team that missed last quarter's new customer meetings target.