  Upper-extremity amputees who use myoelectric prostheses currently lack the
haptic sensory information needed to perform dexterous activities of daily
living. While considerable research has focused on restoring this haptic
information, these approaches often rely on single-modality feedback schemes
which are necessary but insufficient for the feedforward and feedback control
strategies employed by the central nervous system. Multi-modality feedback
approaches have been gaining attention in several application domains, however,
the utility for myoelectric prosthesis use remains unclear. In this study, we
investigated the utility of dual-modality haptic feedback in a virtual
EMG-controlled grasp-and-hold task with a brittle object and variable load
force. We recruited N=20 non-amputee participants to perform the task in four
conditions: no feedback, vibration feedback of incipient slip, squeezing
feedback of grip force, and dual (vibration + squeezing) feedback of incipient
slip and grip force. Results suggest that receiving any feedback is better than
receiving none, however, dual-modality feedback is far superior to either
single-modality feedback approach in terms of preventing the object from
breaking or dropping, even after it started slipping. Control with
dual-modality feedback was also seen as more intuitive than with either of the
single-modality feedback approaches.
