Haptic Serial Dependence in Roughness Perception and Pleasantness.

Our perception does not consist of isolated events but unfold and adapt over time, forming a continuous stream of experience. How we perceive an object is influenced not only by its intrinsic characteristics but also by our recent interactions, leading to sequential effects (i.e., serial dependence). In this study, we investigated whether such effects occur in haptic material perception, specifically in pleasantness and roughness. We also examined whether serial dependence is grounded in the physical object properties or the task at hand (i.e., perceptual attribute). To this end, we used seven sandpaper samples ranging in roughness (18.3 to 425 microns). In two separate sessions, individuals explored the samples with their index finger and rated how pleasant or rough each object feels. Our results revealed a significant attractive serial dependence in roughness judgments and a weaker repulsive serial dependence in pleasantness judgments. This shows distinct patterns of serial dependence for roughness and pleasantness emerging for the same physical stimuli. These divergent patterns for the same stimuli suggest that serial dependence in haptics is attribute-dependent, reflecting higher order mechanism rather than being purely driven by stimulus characteristics. Recognizing the role of serial dependence in haptics opens new avenues for haptic interfaces and engineering user experiences.