Abstract
Body-machine interfaces, i.e. interfaces that rely on body movements to control external assistive devices, have been proposed as a safe and robust means of achieving movement and mobility; however, how children learn these novel interfaces is poorly understood. Here we characterized the learning of a body-machine interface in young unimpaired adults, two groups of typically developing children (9-year and 12-year olds), and one child with congenital limb deficiency. Participants had to control the end-effector of a robot arm in 2D using movements of the shoulder and torso. Results showed a striking effect of age - children had much greater difficulty in learning the task compared to adults, with a majority of the 9-year old group unable to even complete the task. The 12-year olds also showed poorer task performance compared to adults (as measured by longer movement times and greater path lengths), which were associated with less effective search strategies. The child with congenital limb deficiency showed superior task performance compared to age-matched children, but had qualitatively distinct coordination strategies from the adults. Taken together, these results imply that children have difficulty learning non-intuitive interfaces and that the design of body-machine interfaces should account for these differences in pediatric populations.
Highlights
As the number of children needing assistive devices for mobility and manipulation increases[1], the need for developing effective methods for the control of assistive devices such as a prosthetic arm remains a priority
Because body-machine’ interface (BoMI) rely on mapping residual body movements to the control of an external device, this mapping between body movements and the control of an external device can sometimes be non-intuitive, which may limit the ability of children to use these interfaces
The percentage of participants who were able to complete the full experiment varied differed between age groups, with the 9-year old group having the greatest difficulty with completing the task
Summary
As the number of children needing assistive devices for mobility and manipulation increases[1], the need for developing effective methods for the control of assistive devices such as a prosthetic arm remains a priority. In contrast to brain-machine interfaces, BoMIs rely on picking up existing body movements to control external devices Because these movements can be picked up using small wireless devices (such as inertial measurement units), they possess a number of advantages including being completely non-invasive, having good signal properties (i.e. high signal-to-noise ratios and low drift), and being wearable. There is an issue of learning to accommodate delay - unlike the cursor which is a virtual object with zero inertia that can move instantaneously, the robot arm is a physical object with inertia and associated time delays in the response This difference may affect the learning strategy because there is evidence that adapting to these delays in an interface can be challenging[19,20,21]. Based on the results from our prior study[15] we examined if there were differences in movement exploration between children and adults when using velocity-control
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