Tipping Points

From Uber to Instacart to DoorDash, apps have revolutionized the service economy. But do the real-time feedback ratings customers give providers have any impact on tipping?

Researchers at the Carlson School of Management set up field studies to analyze how rating services impact tipping behaviors. Their results show that the size of tips decreases by an average of 17 percent when customers are asked to rate service before tipping. And that’s not just with apps. The researchers conducted a study at a Twin Cities Chinese restaurant, where customers were asked to rate service in order to help the restaurant determine its employee of the month. Tips decreased by 13 percent after customers rated the service.

Why? Researchers think that customers believe a service ranking is in and of itself a benefit to the employee, and therefore don’t feel as motivated to reward them financially. If a customer believes an employee benefits directly from the rating, they are less likely to be generous with tipping.

On the other hand, when customers were reminded of their scores—say in a follow-up text—they tipped more.

“People have commitment and consistency motivations, which urge customers who give high ratings to tip more,” said Carlson School Associate Professor Alison Xu. “If I were to rate the driver five stars but decide to give no tip at all, that can be inconsistent. But by reminding the customer about the high rating, the motivation to be consistent is now at the top of their mind.”

This study was published in the June 2022 issue of Journal of Marketing.

Thought Power

Researchers at the U of M’s College of Science and Engineering are using artificial intelligence (AI) technology to help amputees control prosthetic arms using their thoughts.

Previously, amputees could operate prosthetics through microchip devices implanted in their muscles. The breakthrough developed at the University uses chip technology implanted in the peripheral nerve in a person’s arm, and synchs the chip with AI software to help interpret signals from the nerve. 

“With other commercial prosthetic systems, when amputees want to move a finger, they don’t actually think about moving a finger. They’re trying to activate the muscles in their arm, since that’s what the system reads,” says Jules Anh Tuan Nguyen (Ph.D. ’21), a postdoctoral researcher in CSE. “Our technology knows the patient’s intention. If they want to move a finger, all they have to do is think about moving that finger.”

It’s a breakthrough researchers say could pave the way for advances in helping not only amputees, but people with a host of neurological disorders and chronic pain.

This research was first published in the October 2021 issue of Journal of Neural Engineering.

Bacterial Bullseye

Known as “forever chemicals,” PFAS are a class of polyfluorinated chemicals that make everyday life easier, from the coating on nonstick pans to water-repellent rain gear. They have also been linked to an increased risk for serious health conditions—from testicular cancer to thyroid disease to miscarriages.

PFAS are also notorious for accumulating in soil and water. And because they aren’t naturally occurring in nature, they usually don’t break down.

But Maddy Bygd, a graduate student in the U of M’s microbial engineering program, together with Distinguished McKnight University Professor of Biochemistry, Molecular Biology and Biophysics Larry Wackett, has identified a bacterium that can break down these chemicals and turn them into harmless fluoride and carbon.

Using a new method she devised, Bygd identified a bacteria called Pseudomonas putida F1, which is a promising candidate to remediate PFAS in soil because it is naturally occurring and has been shown to break down compounds that resemble PFAS.

This research first appeared in the December 2021 issue of mBIO.