Sometimes, there’s nothing more soothing than the loving presence of a loving pet. A cat nuzzling against your leg or a dog resting its head on your lap can melt away the day’s stress. But what if a robot could do the same? Inspired by the gentle head-butting behavior of household animals, researchers at the University of Tsukuba in Japan have developed a robotic device designed to replicate this comforting gesture.

Their goal: to see if a machine can offer the same psychological relief as a living, breathing companion.

Their results suggest that robots might indeed have a place in our emotional lives. After interacting with the robot, participants reported a significant drop in tension. While the study is preliminary, it opens up intriguing possibilities for the future of human-robot interaction, particularly in therapeutic settings.

A robot pet?

The robot, developed by Yuga Adachi and Fumihide Tanaka, was inspired by a behavior known as bunting. In the animal kingdom, bunting is a form of tactile communication. Cats, for example, rub their heads against objects — or people — to mark their territory or express affection. This gentle contact has been shown to reduce stress and anxiety in humans, making it a key element of animal-assisted therapy.

But animals aren’t always practical. Allergies, the risk of bites or scratches, and the potential for disease transmission can make pet ownership challenging for some. Robots, on the other hand, while safe and controlled, are lifeless, cold, and difficult if not impossible to form an emotional bond with. Nevertheless, the Japanese researchers set out to create a robot that could replicate the soothing effects of bunting.

Their first prototype was a simple device with a furry head that could tilt and rub against a person’s body. While participants found the robot’s movements endearing, some noted that the force of the rub felt weaker than that of a real cat. Building on this feedback, the researchers developed a second prototype with a more advanced design.

This second version featured a flexible neck capable of changing its stiffness, mimicking the way animals adjust their movements during physical contact. The robot’s head could now press against a person with varying levels of force, creating a more lifelike interaction.

Testing the Robot’s Soothing Effects

To evaluate the robot’s impact, the researchers recruited 22 participants and divided them into three groups. Each group experienced the robot’s head-rubbing motion under different stiffness conditions: low, high, or variable. Before and after the interaction, participants completed a psychological assessment to measure their mood, particularly their level of tension.

The results were striking. Across all groups, participants reported a significant reduction in tension after interacting with the robot. While there was no clear difference between the stiffness conditions, some participants noted that the variable stiffness made the robot’s movements feel more natural and relaxing.

“I thought the force was changing and seemed real; so, this behavior was the most relaxing,” one participant commented. Another remarked, “This movement felt lifelike and natural because it had stronger and weaker forces compared to the other conditions.”

These observations suggest that the subtle variations in stiffness could enhance the robot’s ability to mimic animal behavior, making the interaction feel more authentic.

The Future of Therapeutic Robots

The research lacked a control condition, making it difficult to pinpoint the exact source of the tension reduction. Was it the robot’s physical contact, its lifelike movements, or simply the novelty of the experience? Future studies will need to address these uncertainties and limitations.

The researchers speculate that using more elastic materials or dynamic control of the robot’s movements could enhance the user experience. Nevertheless, robots like this could one day serve as therapeutic tools, offering comfort to those who cannot have pets or providing additional support in settings like hospitals and nursing homes.

Would you find a robot-pet useful? Or is this just something that could only work in, you know, Japan?

The findings appeared in the journal ACM Transactions on Human-Robot Interaction.