Integration of Force and Position Cues in Haptic Curvature Perception

When one slides a finger across a surface with a bump on it, the finger follows the geometry of the bump, providing positional cues for the shape. At the same time, the finger is opposed by forces related to the steepness of the bump. With a specific device, Robles-de-la-Torre and Hayward (2001) dissociated positional and force cues in the haptic perception of small-scale bumps and holes: Participants in this experiment reported feeling the shape indicated by the force cues and not those indicated by the positional cues. We extended this research by systematically disentangling the contributions of these two cues to the perception of curvature. Using the PHANToM haptic device, we presented virtual curves, in which we intermixed force and position cues related to curvatures between 0 and 16/m. Participants compared these with pseudonatural curves. Our results suggest that perceived curvature is a weighted average of both positional and force cues