Difference in Haptic Softness Estimation using Pressing and Pinching

People systematically use different touch strategies to perceive different object features. When interacting with a deformable object, human typically judge the softness by pressing the finger pad into the surface or pinching the object with the thumb and index finger. However, the link between touch strategy (e.g., pressing) and haptic softness perception needed to be explored. To ascertain how people's perceptions of softness are impacted by touch strategy, experiments on estimating softness were undertaken in the current study. Nineteen subjects were instructed to understand how to estimate the softness of a variety of haptic stimuli with varied elastic moduli by pressing and pinching. The results indicate that subjects were able to scale softness regardless of the touch strategy. However, the functions for scaling softness were affected by the touch strategy; the estimation of softness was greater with pinching. It suggests that the haptic perception of softness was affected by touch strategy. Additionally, the slopes of the functions were greater in the pressing group. This finding suggests that subjects in the pressing group showed better softness discrimination.