Haptic adjustment of cylinder radius

Haptic curvature discrimination experiments have typically been done with relatively small stimuli (at most hand-sized) placed on a table. In daily life, however, we often handle large curved objects (think of basket balls), which we usually hold with two hands. Here, I focus on the question how well shape information from the two hands is integrated. I investigated subjects’ ability to adjust the distance between two large cylindrical shells in such a way that the two shells together would perceptually form a circular cylinder. All subjects were able to perform this task in a consistent way, but adjustments were often far from veridical. As deviations were often larger than discrimination thresholds, I hypothesize that they are either due to systematic biases in curvature perception or to misestimations of the distance between the hands. These results contribute to our understanding of haptic shape perception.