Sufficiency of longitudinal moment of inertia for haptic cylinder length judgments.

Many studies invoke moment of inertia (Iii) as necessary and sufficient information to perceive cylinder length via wielding, yet some assert that Iii is neither necessary (weight, m, or static moment, M, are sufficient) nor sufficient for length judgments (m or M is necessary). Mathematical expressions for Iii not involving m or M imply length, so Iii could be sufficient for cylinder length judgments. In 5 experiments (N = 113), only longitudinal Iii (the smallest principal value) informed cylinder length estimates in a novel task, rolling. Experiment 1 yielded reliable length judgments. Varying diameter supported length scaling (Experiment 2); similar length estimates occurred with both rolling and wielding (Experiment 3); feedback improved rolling length judgments to levels commensurate with wielding (Experiment 4); and length judgments shifted predictably with added mass (Experiment 5). Contrary to proposals in the literature, Iii is sufficient information for cylinder length judgments, absent m or M information, even when Iii is of minimal magnitude and the task quite novel. Copyright 2010 APA, all rights reserved.