Physically interacting humans regulate muscle coactivation to improve visuo-haptic perception

TL;DR

This study investigates how physically connected humans adapt muscle coactivation to optimize visuo-haptic perception, balancing stiffness, effort, and sensory information during joint movement tasks.

Contribution

It reveals that humans adapt muscle coactivation based on visual feedback quality, challenging previous models focused solely on movement error minimization.

Findings

Muscle coactivation increases with worse visual feedback.

Humans control arm stiffness to optimize sensory information and effort.

Adaptive muscle regulation enhances visuo-haptic perception.

Abstract

When moving a piano or dancing tango with a partner, how should I control my arm muscles to best feel their movements and follow or guide them smoothly? Here we observe how physically connected pairs tracking a moving target with the arm modify muscle coactivation with their visual acuity and the partners performance. They coactivate muscles to stiffen the arm when the partners performance is worse, and relax with blurry visual feedback. Computational modelling show that this adaptive sensing property cannot be explained by movement error minimization proposed in earlier models. Instead, individuals skilfully control the arms stiffness to guide it on the planned motion while minimizing effort and extracting useful haptic information from the partners movement. The central nervous system regulates muscles' activation to guide motion with accurate task information from vision and haptics while minimizing the metabolic cost.