Imagine you strike up a conversation with a stranger in line at the grocery store or the airport one day and quickly notice that she has a large smudge of dirt across her cheek. Would you tell her about the potentially embarrassing mark? 

Most of us would certainly like to know if we're walking around in public with dirt on our face. And probably most of us, especially take-charge entrepreneur types, would like to think we'd help a stranger out with a discreet heads up if they were unaware of an embarrassing issue.

But when a team of Harvard researchers actually tested this scenario in real life, sending a confederate out to question passersby for a survey with a large lipstick or chocolate smear across his or her cheek, do you want to guess how many people actually informed the clipboard-wielding stranger about the problem? 

The correct answer is all of 2.6 percent. Only four out of 155 people said anything. If that result shocks you, you're not alone. The researchers themselves were surprised by the findings, which they insist offer leaders important lessons about giving constructive feedback

You are underestimating how much people value feedback. 

"This surprised us because we didn't expect the number to be so low. I think we all like to think of ourselves as someone who would give someone feedback in this kind of situation, but our study showed that most people don't," study co-author Nicole Abi-Esber told PsyPost

To find out why our behavior so frequently fails to live up to our ideals in this kind of situation, Abi-Esber and her colleagues ran a series of follow-up experiments using both real-life set ups and fictional scenarios to figure out how people think through when and how to give constructive feedback. 

Each experiment yielded roughly the same results: People consistently underestimate how much other people will appreciate feedback. Whether we're dealing with close friends or complete strangers, we frequently misperceive how much impact our feedback will have and how much the other party generally wants to be given advice to improve. 

This was particularly true in higher-stakes situations. For instance, when the researchers ran a speaking competition with the prize of a $50 Amazon gift card, those charged with coaching speakers seriously underestimated how much their partners wanted feedback to improve. The gap between real and expected desire for feedback was smaller in lower stakes situations, like someone having food stuck in their teeth. 

The dead simple takeaway 

The real-world lesson here according to the researchers is dead simple: Leaders and others in a position to give useful feedback should offer more. "Even if you feel hesitant to give feedback, we recommend you give it: the person most likely wants it more than you think," Abi-Esber advises. 

If you're nervous the other person might react badly even after reading this research, just ask yourself, "If I were this person, would I want feedback?" This simple question was shown to improve people's willingness to give feedback during the research. 

Of course, working up the courage to provide constructive feedback is only part of the process. Great leaders also need to know how to deliver it effectively. This particular study doesn't speak to that issue, but plenty of other experts have. We've written about this advice often here on Inc.com

All these tips and formulas for better feedback are useful onlyif you can actually bring yourself to open your mouth though. So whenever you doubt whether your feedback will be well received, spare a thought for this study and that poor research assistant left standing on a college green with lipstick smeared across her cheek. That should encourage you to give the feedback your team both needs and wants