2009 年 8 巻 4 号 p. 1105-1111
When touching an object, the forefinger pad is deformed based on the hardness of the object, and we consider that slight deformation influences hardness sensation. To clarify the influence of deformation of forefinger pad on hardness sensation, we compared hardness sensation in two conditions with different deformation of the forefinger pad by the method of successive categories. Fourteen elastic test pieces with different hardness were evaluated by eleven subjects based on seven stages of hardness sensations (extremely soft, fairly soft, slightly soft, neither, slightly hard, fairly hard, extremely hard) for the conditions of direct touching of test pieces or touching using an acrylic plate. This results indicated that subjects were capable of perceiving slight differences in hardness within three categories (fairly soft, slightly soft, and fairly hard) for direct rather than indirect touch. Deformation of the forefinger pad based on the hardness of an object may thus influence hardness sensation when the hardness of an elastic object is classified into these three categories.