Issuing new challenges — even if they're difficult — can make your employees feel more engaged and satisfied at work.

One of the toughest jobs of managers and executives is to figure out how to engage their employees. According to Gallup's State of the Global Workplace report, only 13 percent of people around the world feel engaged at work.

Some companies may try to boost employee perks like free food or fun social events, but Liz Wiseman, the author of Multipliers: How the Best Leaders Make Everyone Smarter, suggests a less obvious way of engaging employees: make them do something hard.

In a Harvard Business Review article, Wiseman cites a survey by the Society for Human Resource Management that found the top driver of job satisfaction is "the opportunity to use skills and abilities." Wiseman posits that employees not only want their skills to be used at work, but they want to be challenged to expand those skills.

While researching her book Rookie Smarts, Wiseman surveyed 1,000 people from a variety of industries and found a strong correlation between those who felt challenged at work and those who felt satisfied. The survey also discovered that people were often ready for a new challenge sooner than you might think. That puts the burden on managers to anticipate when an employee needs a new challenge before he or she starts feeling bored and disengaged.

As a leader, you should look out for the following signs to determine when employees are ready for a new challenge: Everything they manage has run smoothly for a while; when they encounter a problem they quickly find a solution; they try to fix other problems at the office from different departments; and they've become inexplicably negative. If you notice an employee who fits this description, it's probably time to assign them a new challenge.

Once you recognize that need, Wiseman suggests three different ideas for how to make the employee feel challenged:

• Give them more difficult and more complex assignments, but don't ask them to juggle too much. Expand on the work they're already doing.
• Invite them to work on something they are unfamiliar with, something outside their regular expertise. Let them learn as they go and become more comfortable with the new project and master new skills.
• Have them apply their expertise to a new problem. Wiseman gives the example of asking a scientist at a pharmaceutical company to shift from cellular biology to oncology.

The key is to make sure you're not stretching your employees too far. But if you can strike the right balance, they are bound to be more satisfied with their job.

"Although it's important for your employees to stop and celebrate success or just catch their breath, they might also be ready for the next challenge sooner than you think," Wiseman writes. "Pay raises, bonuses, and promotions are limited.  Challenging work — assignments your employees can sink their teeth into — is not."