As more fast-food chains experiment with artificial intelligence at the drive-thru, a new study suggests the technology itself may influence what people order.
Researchers at Pennsylvania State University found that participants were more likely to choose an indulgent meal option when interacting with a voice AI system compared with a human employee. The findings were published in the International Journal of Hospitality Management.
In the first experiment, 117 participants were randomly assigned to watch a short video simulating a drive-thru ordering experience. Some interacted with a human employee, while others interacted with voice AI. Participants then chose between two meal options: a cheeseburger and fries or a grilled steak salad with fruit.
The voice AI group selected the indulgent option at higher rates.
“These findings are impactful because it shows technology may not be neutral,” said Chandler Yu, associate professor of hospitality management at Penn State and co-author of the study. “Even small design features — like whether customers interact with a human, an AI voice or AI with an avatar — can change decision making in meaningful ways. It helps explain why AI systems may unintentionally encourage indulgence.”
In a second experiment with 123 participants, researchers explored why this effect might occur. They measured cognitive depletion, or mental fatigue, after participants completed the simulated ordering task.
Interacting with voice AI appeared to increase mental strain. Unlike a human conversation, voice-only AI requires people to pay closer attention, monitor whether they are understood and process information without normal social cues. That extra effort may reduce the mental energy available for self-control.
“We found when people are mentally tired, they are less likely to think carefully and more likely to go with what feels good right now,” Yu said. “Choosing something healthy takes more mental effort and self-control. Indulgent foods provide quick comfort and immediate pleasure.”
In a third experiment involving 164 participants, the researchers tested whether adding a human-like avatar to the AI system changed outcomes. Pairing voice AI with an on-screen avatar reduced the indulgence effect, suggesting that small design features may help offset mental fatigue.
It is important to note that participants were making hypothetical choices after watching a one-minute video simulation. The study did not measure real-world purchasing behavior at actual drive-thrus. Still, the results highlight how subtle aspects of the eating environment, including technology interfaces, may shape food decisions.
For consumers, the takeaway is less about avoiding AI and more about awareness. After a long day, when mental energy is low, people may default to options that provide immediate comfort. Whether ordering from a person or a machine, decision fatigue can nudge choices in predictable directions.
As AI becomes more integrated into everyday life, the researchers say understanding how interface design influences behavior will be increasingly important, especially in settings tied to health.
The research was supported by the J. Willard and Alice S. Marriott Foundation.