Integration of force and position cues for shape perception through active touch

This article systematically explores cue integration within active touch. Our research builds upon a recently made distinction between position and force cues for haptic shape perception [Robles-de-la-Torre, G., Hayward, V., 2001. Force can overcome object geometry in the perception of shape through active touch, Nature 412, 445–448]: when sliding a finger across a bumpy surface, the finger follows the surface geometry (position cue). At the same time, the finger is exposed to forces related to the slope of the surface (force cue). Experiment 1 independently varied force and position cues to the curvature of 3D arches. Perceived curvature could be well described as a weighted average of the two cues. Experiment 2 found more weight of the position cue for more convex high arches and higher weight of the force cue for less convex shallow arches—probably mediated through a change in relative cue reliability. Both findings are in good agreement with the maximum-likelihood estimation (MLE) model for cue integration and, thus, carry this model over to the domain of active haptic perception.