Crossmodal Texture Perception Is Illumination-Dependent

Area of Science:

• Psychology
• Neuroscience
• Perception

Background:

• Visual perception of 3D texture roughness is known to vary with illumination direction.
• This phenomenon, a lack of roughness constancy, leads to surfaces appearing rougher under lower angles of light.
• It remains unclear if the visual system can access illumination-invariant features for roughness judgment or if it relies on illumination-dependent cues.

Purpose of the Study:

• To investigate if the visual system relies on illumination-dependent features for roughness judgment in crossmodal tasks.
• To determine if the visual system can access illumination-invariant surface features evaluated by the tactile system.
• To examine the transfer of illumination-dependent visual roughness perception to crossmodal matching.

Main Methods:

• Participants (N=32) explored abrasive paper tactually or visually under top and oblique illumination.
• They performed intramodal (same modality) and crossmodal (different modality) matching tasks.
• Comparison stimuli varied in physical roughness to assess perceived roughness.

Main Results:

• Intramodal matching performance was consistent across modalities and illumination conditions.
• In crossmodal tasks, visual exploration under oblique light led to selecting rougher tactile matches compared to top light.
• Tactile exploration under oblique light resulted in selecting smoother visual matches compared to top light.

Conclusions:

• Visual roughness perception is dependent on illumination direction, confirming a lack of roughness constancy.
• This failure of roughness constancy significantly transfers to crossmodal judgments.
• The findings highlight the influence of illumination cues on crossmodal texture perception.