The Effect of Temperature on Tactile Softness Perception

We are adept at discriminating object properties such as softness and temperature using touch. Previous studies have investigated the nature of each object property, but the interactions between these properties are not fully understood. Tactile softness perception relies on multiple sensory cues such as the size of the contact area, indentation depth, and force exerted. In addition to these cues, the temperature of the stimulus may contribute to tactile softness perception by changing the sensitivity to changes in stimulus compliance. To test this hypothesis, we conducted two psychophysical experiments in which the subjects estimated the magnitude of perceived softness after touching deformable objects. We varied the compliance and temperature of the stimuli. The linear functions of compliance fit to the magnitude estimates under cold conditions (9-15°C) were steeper than the functions fit to the magnitude estimates under room temperature (21-25°C). These results indicate that temperature can sharpen our tactile softness perception of deformable surfaces by increasing the sensitivity to differences in compliance.