If you have ever fought off yawns during a video call, don’t be too hard on yourself. Most virtual meetings aren’t stimulating enough to keep people alert.

This isn’t just anecdotal, or something that we intuitively feel. In a study of hundreds of virtual and in-person meetings at two global corporations, we found that lots of people doze off—or find their minds wandering—in online meetings, because the meetings don’t do enough to keep them involved. They are too crowded. They are too long. There is too much lecturing and not enough interaction. So, people sink into drowsiness before long and get much less productive.