In this paper, we investigated the optimum tactual motion for evaluating the texture of various materials. Panels were used to evaluate material texture of six samples, using both active and passive tactual motion, while using one, two or three fingers to conduct the evaluation. We measured the amount of the transmitted information by the information theory to evaluate material texture. We determined the applied force, the dynamical friction force, and the angle between the first finger and objects to understand the role of tactual motion with the experimental process. The results are as follows: (1) From the analysis result of the information theory, the soft/hard feeling was easy to evaluate by both tactual motions. (2) The correlation analysis showed a strong correlation between sensory evaluation and the active tactual motion. The material texture was determined by evaluating the applied force, the dynamical friction force, and the coefficient of dynamic friction.
