Background: Cognition of surface roughness at the same time by the two senses (tactile and
visual) is still undeclared, and how both effects on each other could be intriguing. The main factor for
roughness estimation of fine surface (spatial features below 200 µm) is also unknown until present.
Objective: In order to see the difference between cognition of both condition, we conducted two unimodal
and two bimodal tasks involving both modalities using fine sandpapers. Tactile stimuli consisted of
six types of different sandpapers that varied in their roughness, while visual stimuli are images of the
correspondence tactile stimuli
Methods: In unimodal task, subjects need to compare which stimulus perceived were rougher, visually
and tactually, while multiple sensory of visual and tactile were mixed in bimodal task. We also varied
the type of roughness in bimodal task into two categories to discover whether there is any acceleration
or suppression by different stimuli.
Results: We found that tactile sensory was dominant in the perception of roughness by fine surface. During
cross modalities, visual information has almost no effects toward tactile sensory, but in the other
hand tactile information had significance effects onto visual sensory. Furthermore, we found that stimuli
with smaller particles bring more interference into subject's perception compared to bigger particles in
Conclusion: We suggest that particles sizes are as significant as the modalities in visual, tactile, or multisensory
integration of both, in roughness perception of fine surface.