A person, without benefit of seeing, can come to know about certain properties of objects by wielding and shaking them. Similarly, he or she can come to know about certain properties of unseen surfaces by striking them with a hand-held implement. These instances of knowing about the surrounding environment through the use of the body, known as haptic perception, are based on mechanical forces that distort the body's tissues in complex ways. Presumably, for each perceived environmental property, there is a specific mechanical property. Identifying these mechanical properties, and understanding exactly how people use them to measure spatial characteristics of the adjacent environment, pose significant challenges. These experiments will examine how people use the inertia tensor as the mechanical basis for the haptic perception of the lengths, shapes, and orientations of unseen objects wielded by hand, and they will examine how people use the resultant of reactive forces as the mechanical basis for the haptic perception of the distance between struck surfaces. This research will also examine patterns of wielding, looking for a relation between the particular way an object is wielded and the object property the person is attempting to measure. The participants in the experiments will respond by adjusting visible, moveable surfaces to quantify the perceived properties. Results could provide insights valuable in the design of sensory and motor prostheses, robotic limbs, and "smart" remote-sensing instruments.
