Here in the dog days of summer, when many of us are wishing we had had the foresight to be born French so we could spend the month on a beach, peak productivity might be a little harder to achieve than usual. Not that it isn’t also a hot topic the rest of the year: Apple’s App Store offers no fewer than 3,700 applications designed to help users tackle their to-do lists, and a quick online search turns up more than 5,000 books on how to boost productivity published since 2011 in the U.S. alone.

Even so, it seems most managers handle two big productivity problems—procrastination and missed deadlines—all wrong. At least, that’s the conclusion of a new study from researchers at four B-schools.

Here’s a quick quiz: When a member of your team puts off a project until the deadline has sailed past, do you a) assume he has too many things to do and take away some of his workload so he can concentrate better on the task at hand, or b) simply set a new deadline, without reducing his total number of tasks?

Most well-intentioned bosses would choose a), but the better answer is b). “When people miss a deadline, they usually feel bad about it. They feel guilty and maybe embarrassed,” notes Andrew T. Stephen, a professor at the University of Pittsburgh’s Joseph A. Katz Graduate School of Business, who led the study. Those emotions “are demotivating. Once someone starts associating negative feelings with a task, it just makes it even harder to get the damn thing done.”

By contrast, when people who blow a deadline have plenty of other work on their plates, besides the project they didn’t finish on time, “they don’t get as demotivated,” Stephen says. “They can excuse their failure to finish this one thing on time by telling themselves, ‘Well, I had 10 other things going on.’ It takes the edge off, and makes it easier to complete that task.”

Based on an analysis of 586,808 data points from a productivity app, a field study of 250 people over two consecutive weeks, and two controlled lab experiments, the research was nothing if not thorough, and it yielded a few other insights.

For one thing, the absolute number of tasks someone has to do isn’t as important as whether or not she perceives herself to be busy. So, to make people less prone to procrastinate, Stephen says managers might want to help boost employees’ feelings of “busy-ness,” without actually piling on any more work.

“One approach is to break each project down into many component parts, with separate deadlines, so that someone feels they’ve got 10 things to do instead of just one,” he says, adding that “many people tend to do this for themselves anyway, partly because it makes a task seem more manageable.”

Stephen is careful to point out that the study’s definition of “busy-ness” is not the same as multitasking, which usually reduces productivity. “We’re also not recommending overloading anyone to the point where they’re like a deer in headlights and can’t function,” he says. “But do resist the temptation to let people—especially procrastinators—be less busy. It won’t help.”