Analyzing grasping for inferring cognitive states of users

We study the effect of cognitive states, feelings about tasks, on grasping behavior to estimate user's feelings from their motion. Since people solve the inverse kinematics problem of grasping based on their cognition for the task, when they grasp an object, the way to grasp the object reflects their cognitive states. We are analyzing the way of grasping a cup depending on whether a user is stressed. The physical properties of grasping, volume and entropy of Grasp Jacobian ellipsoids are analyzed. The volume of Grasp Jacobian ellipsoids, which indicates the possible size of object movement, was shrunk after learning the grasp motion. Also the volumes between the relaxed and the stressed cognitive conditions were significantly different. These results show that the user's cognition for tasks reflects the grasp forms and the possible size of object movement.