Basic Study of the Influence of the Manner of Grasping, Number of Contacts, and Auditory Information on Recognition of Hardness of Objects by Visually Impaired Persons Using White Canes

Abstract

White canes are widely used as tools to assist visually impaired persons to walk. The white cane is used to acquire environmental information as a clue for walking. It is important to know what information can be acquired by using the cane, how accurate the acquired information is, and how we can improve the information and accuracy. Clarification of these questions would contribute to development of white canes that enable better acquisition of environmental information. It would also assist in the design of buildings with appropriate guidance for visually impaired persons on the basis of information acquired through the canes. In this study, in order to acquire basic knowledge about hardness recognition, experiments were performed using four conditions: 1) Tapping or pushing the object with the index finger tip and white cane tip, 2) use or non-use of the auditory sense to study its usefulness, 3) different ways of grasping the cane, and 4) different number of checks. Nine visually impaired persons who usually walked alone using white canes participated in the experiments. They estimated the hardness of a rubber sheet under various combinations of the operation conditions and hearing conditions. Results showed that the number of checks had little effect on the user’s estimation of the hardness of the sheet. For the recognition of the contact target hardness using the white cane, it was effective to simultaneously use information from different modalities, namely tactile and auditory information. We also observed that, when pushing the cane with the index fingers, the users could feel the objects as if they had directly touched them with the fingers.