With unemployment at the lowest it has been since 2008, you might be thinking about changing jobs. But what exactly would make you happier at work? It’s not necessarily free meals and massages (though those are nice, as companies on Fortune’s list of the Best Companies To Work For have figured out). And it’s not even necessarily lots more money. We’ve scoured the research and identified five science-backed attributes that make people happy at their jobs.

1. Work that challenges you.

Research finds that people are happiest when engaged in difficult-but-doable activities. They are so absorbed in their tasks that time seems to stand still. It’s easy to drift away from real work in the rush to empty the inbox, but you can get back on track. Brian Tracy, author of numerous career books including Find Your Balance Point, recommends taking advice from Japanese decluttering expert Marie Kondo’s run-away bestseller, The Life-Changing Magic of Tidying Up. “She says put everything in a heap, and pick each item up, and ask ‘does this item spark joy in me?’” You can do this with your job too. “Instead of being passive and doing what someone else told you to do, actively look at your work and ask what would I really like to do?” Tracy suggests. With a little creativity, over time, you can turn the job you have into the job you want.

2. A sense of progress.

When Harvard Business School professor Teresa Amabile and psychologist Steven Kramer studied diaries from nearly 12,000 work days, they found that the happiest and most productive days were those marked by a sense of progress. “Ultimately, work is really about accomplishment,” says Richard Sheridan, CEO of Menlo Innovations, and author of Joy, Inc. “Did I get something done, and does it matter?” His team members meet with clients weekly for an inverse status meeting: the client recounts what the team did during the past week, with whatever commentary he or she desires. Seeing impact gives the team “a real sense that what we did mattered.”

A related point: progress is the opposite of distraction. “If you’re wasting time all day with distractions, then you don’t finish tasks,” says Tracy, and “human beings are designed to get a feeling of pleasure from closure.” Time out of the inbox can do wonders for well-being. Indeed, one study that involved cutting off email access for 5 days found workers’ stress levels dropped.

3. No fear.

Sticks may motivate people in the short run, but if employees worry that their jobs are on the line, research finds that they become less engaged and performance suffers. “Fear has this debilitating effect on safety, on trust, on team work, on collaboration, on creativity, innovation, and invention,” says Sheridan. This doesn’t mean there can’t be accountability. People who aren’t performing and won’t take coaching need to be moved out. Likewise, “there are things we should be afraid of,” Sheridan says. Disappointing a big client is one of those things. But, “What I’m talking about is using manufactured fear as a way to motivate people.” It just makes employees miserable.

4. Autonomy.

One meta-analysis involving over 400,000 people in 63 countries found that autonomy and control over one’s life matters more to happiness than money. In a work context, this requires a sense of control over your work, but — just as important — over your time too. Flexibility is key, and employees with flexible work schedules report better well-being than those with less control over time and place.

5. Belonging.

Humans are social creatures, and Gallup’s research has found that people who have a “best friend” at work are more productive and engaged. Real relationships are hard to manufacture, but relaxed interaction does breed familiarity over time. This argues for taking the team out for lunch or coffee as often as you can. You can also simply knit friendship-building into the fabric of the day, doing things that build your relationship capital. Bill Jensen, CEO of consulting firm The Jensen Group, adopts what he calls a “3-2-1” rule for his days. He focuses on his top 3 to-dos, the “one” refers to learning something, and then he includes “two pay it forward moments every day, helping others” he says. “Each of these daily to dos feed into and build long-term happiness.”