A missed birthday. A forgotten anniversary. A milestone that goes unnoticed. These small slights from a manager may seem like no big deal, but new research from Wharton reveals that even the mildest mistreatment at work can affect more than just employee morale.

The study found that when managers at a national retail chain failed to deliver birthday greetings on time, it resulted in a 50% increase in absenteeism and a reduction of more than two working hours per month. The lost productivity was a form of revenge, with slighted employees taking more paid sick time, arriving late, leaving early, and taking longer breaks.

“Insults are about a lack of respect, and that’s what this is really about. There are huge and small lacks of respect, but they all leave a mark,” says Wharton management professor Peter Cappelli, who conducted the study with Liat Eldor and Michal Hodor, assistant professors at Tel Aviv University’s Coller School of Management.

“The Lower Boundary of Workplace Mistreatment: Do Small Slights Matter?” appears in the journal Proceedings of the National Academy of Sciences. While there are a growing number of papers that examine the effects of severe workplace mistreatment such as sexual and physical harassment, the study is the first to measure the cause and effect of minor infractions.

‘There are huge and small lacks of respect, but they all leave a mark.’
—Peter Cappelli

Why a small slight can be a big deal

Cappelli says he and his co-authors wanted to explore how an “absolute minimum” of bad behavior would result in problems at work, but doing so outside of a laboratory experiment proved challenging. They found the perfect observational setting in the retail chain, which has a well-established policy that managers hand-deliver a card and small gift to each employee on their birthday. The company designed the policy to foster meaningful personal interactions and strengthen the employee-manager relationship.

The chain of 252 stores also kept detailed data on employee performance and other metrics, making it ideal for study, Cappelli says.

The team found no issues when cards and gifts were given within a five-day window of the employee’s birthday. But productivity losses occurred when the gift was given outside of that time. Absenteeism returned to normal levels once the gift was received.

“This is pretty trivial, but it’s still a problem,” Cappelli said. “The boundary condition seems to go so low that even a very small slight that we don’t think of as a big deal still matters to people’s job performance.”

‘Giving somebody a birthday card and getting it to them on time is good manners.’
—Peter Cappelli

A lesson in perspective-taking

In addition to the data analysis, the scholars surveyed managers about why they might fail to deliver on time. The faux pas was never intentional; the managers who were late said they had other operational or profit-related priorities. Both managers and human resources staff acknowledged that deliberately delaying a gift as punishment was inappropriate and not part of their reasoning.

Cappelli says the company was surprised to learn that such a small insult could affect productivity, especially since delays weren’t intentional. He says the results offer a lesson in perspective-taking for managers everywhere.

“The employers were surprised because they didn’t do it on purpose. But from the employee’s perspective, they were like, ‘All you had to do was hand me the card,’” Cappelli says. “It’s a different perspective on the same phenomenon.”

In their paper, the professors emphasize that managers aren’t solely responsible for employee mistreatment. However, the study serves as a reminder that interpersonal skills are essential for managers, and that workplaces have a vested interest in mitigating harm to their employees. An easy place to start is simply acknowledging what’s important to people outside of their jobs: birthdays, graduations, marriages, a new baby, death of a loved one, or religious observances. Doing so makes them feel valued as human beings, not just human capital.

“I think it is about personal relationships,” Cappelli says. “Giving somebody a birthday card and getting it to them on time is good manners. And manners matter.”

Published Dec. 8, 2025, by Knowledge at Wharton.