Grip Force-Load Force Coupling Is Influenced by Altered Visual Feedback about Object Kinematics

Abstract

Recent evidence suggests that visual feedback influences the adjustment of grip force to the changing load force exerted by a grasped object as it is manipulated. The current project investigated how visual feedback of object kinematics affects the coupling of grip force to load force by scaling the apparent displacements of the object viewed in virtual reality. Participants moved the object to manually track a moving virtual target. The predictability of the changing load force exerted by the object was also manipulated by altering the nature of target trajectories (and therefore the nature of object motions). When apparent object displacements increased in magnitude, grip force became more tightly coupled to load force over time. Furthermore, when load force variations were less predictable, the magnitude of apparent object displacements affected the relative degree of continuous versus intermittent coupling of grip force to load force. These findings show that visual feedback of object motion affects the ongoing dynamical coupling between grip force control and load force experienced during manipulation of a grasped object.

Keywords:

• Coordination
• force control
• grasping
• visual feedback

Acknowledgments

We would like to thank Maurice Lamb and Patrick Nalepka for their assistance with apparatus and design, and Paula Silva and Tamara Lorenz for their contributions and suggestions to this line of work.

Notes

1 We should note that controlling for friction in this way may have slightly impaired the tactile sensitivity and thus fine motor skills of the participants and our results should be interpreted with this effect in consideration.