The effect of force/motion coupling on motor and cognitive performance

Haptic cues take on meaning as a function of the context in which they are experienced. In interaction with objects in the physical environment, the context always includes a mechanical contact, at which point force and motion variables can be identified, and across which power may flow. In interaction with objects in a virtual or remote environment, it is not necessary for the contact across which haptic responses are rendered to be the same as the contact at which exploratory actions are applied. In this paper, we ask whether force/motion coupling has a significant impact on manual performance or cognitive load. We conducted an experiment in which n=7 participants attempted, while acting through a teleoperator, to discriminate three objects by their stiffness under two conditions. In one condition physical force/motion coupling was present, in the other it was not. To assess cognitive load, we engaged participants in a simultaneous cognitive task that included a response time measure. Results indicated no difference in manual discrimination performance. After rejecting the datasets of three of our participants based on inconsistent strategy by condition, we observed a small, non-significant trend toward lower cognitive load in the condition with physical coupling. Establishing a robust trend will require additional participants. While results are preliminary, we offer our paradigm as an important direction for new inquiry into the distinctions and interrelationships between information and its presentation in various haptic interface applications. Our work is aimed in particular at developing haptic feedback for use in prosthetic applications.