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Supernumerary virtual robot arms can feel like part of our body

Overview: Researchers have developed a virtual robotic arm that can be controlled by a person’s feet in a virtual environment to provide an “extra” limb. After the workout, users reported feeling the virtual limb as if it were part of their physical body.

Source: University of Tokyo

What would you do with an extra arm, or if, like Spider-Man’s nemesis Doctor Octopus, you could have an extra four?

Research into extra or redundant robotic limbs looks at how we can adapt mentally and physically to adding extra limbs to our bodies.

PhD candidate Ken Arai of the Research Center for Advanced Science and Technology (RCAST) at the University of Tokyo became interested in this research as a way to explore the limits of human “plasticity” – in other words, our brain’s ability to change and adapt to external and internal changes.

An example of plasticity is the way we can learn to use new tools and sometimes even come to see them as an extension of ourselves, also known as ‘tool embodiment’, be it an artist’s brush or a hairdresser’s scissors.

To explore these concepts in action, teams from the University of Tokyo, Keio University and Toyohashi University of Technology in Japan collaborated to create a virtual robotic limb system. They then asked the participants to perform tasks in virtual reality (VR) using the virtual limbs.

“We examined whether virtual robotic arms, as redundant limbs, could be seen as part of one’s own body, and whether there would be perceptual changes related to the proximal space around the robotic arm,” Arai says.

Participants wore a head-mounted display to give them a first-person view of their own arms displayed in VR, as well as the additional virtual robotic arms. They then had to perform tasks using only the virtual robotic arms, which were controlled by moving their toes.

Tactile devices sent sensations from the virtual robotic arms back to the tops and soles of the feet when they touched an object, such as a virtual ball.

Once the participants learned how to use the virtual system, they reported feeling that the virtual robotic arms had become their own extra arms and not just extensions of their real arms or feet.

“The subjective evaluation scores were statistically significantly higher for ‘sense of body ownership’, ‘sense of agency’ and ‘sense of self-location’, which are important measures of embodiment where the redundant robotic limb may become part of the body. body,” said Arai.

The team also found that the participant’s “peripersonal space” (the area around our bodies that we consider our personal space) extended to the area around the virtual robotic arms.

This shows a drawing of a robot arm
Research into extra or redundant robotic limbs looks at how we can adapt mentally and physically to adding extra limbs to our bodies. Image is in the public domain

As Arai explained, “We managed to capture the positive association between the perceptual change in visual-tactile integration around the redundant robot limbs (peripersonal space), and the score change of the subjective evaluation of feeling that the number of one’s arms increased. (supernumerary limb sensation).”

Next, the team wants to look at the potential for cooperative behavior between participants’ own arms in virtual reality and the virtual robotic arms.

“Exploring the mechanisms and dynamics of the supernumerary limb sensation reported here from a cognitive neuroscience standpoint will be important in exploring human plasticity limits and designing supernumerary robotic limb systems,” Arai said.

The hope is that by understanding the perceptual changes and cognitive effort required to operate a supernumerary robotic limb system in VR, it will help design real-life systems in the future that humans can use naturally. just like their own bodies.

About this robotics research news

Author: Joseph Krisher
Source: University of Tokyo
Contact: Joseph Krisher – University of Tokyo
Image: The image is in the public domain

Also see

This shows a brain

Original research: Open access.
Embodiment of redundant robot limbs in virtual realityby Masahiko Inami et al. Scientific Reports


Embodiment of redundant robot limbs in virtual reality

The supernumerary robotic arm system extends the motor function of human users by adding additional artificially designed limbs. It is important for us to embody the system as if it were part of one’s own body and to maintain cognitive transparency in which the cognitive load is suppressed. Performance studies have been conducted with an extension of bodily functions through a “substitution” and “extension”.

However, few studies have been done on the “addition” of excess body parts.

In this study, we developed a supernumerary robotic arm system operating in a virtual environment, and then evaluated whether the extra limb can be regarded as a part of one’s own body using a questionnaire and whether the perception of peripersonal space changes with a visuotactile cross-modal. congruence task.

We found that the participants can embody the extra limbs after using the supernumerary robotic limb system. We also found a positive correlation between the perceptual change in the cross-modal congruence task and the subjective feeling that the number of arms had increased (supernumerary limb sensation).

These results suggest that the addition of an extra body part may cause the participants to feel that they have acquired a new body part that differs from their original body part through a functional extension.

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