Tactile perception of two lengths by precision griping with three forefingers

When an object is touched, the properties like shape, temperature, rigidity, texture and weight should be perceived. As a basic research of human tactile, it is most important to know how humans could perceive the shape of the object with forefingers. Thus length and contacting curvature of an object are thought to provide important perception information. Most of the length perception studies are about two fingers using the thumb and the index finger. There are scarce perception studies using multi-fingers grasping. In present study, we develop a tactile length presentation device for two lengths with three forefingers, and investigate the human tactile length perception for two lengths with three forefingers grasping. The results showed that better perception took place when shorter lengths were presented to the thumb and the index finger compared to being presented to the thumb and the middle finger. As a result of force sensor, grip forces show no significant difference in the range of stimulating length.