Happy and sad moods promote global and local visual processing, respectively. However, it is unclear whether mood also affects the processing level in haptics. Here, we used classical music to induce happy and sad moods in blindfolded participants before they scanned printed, flat 2D embossed configurations with their fingers. We also included a neutral group that did not listen to any music. Global shapes were triangles, circles, or squares (33 mm) composed of smaller local relief shapes (3 mm): either triangles, circles, or squares. Participants explored a probe stimulus with identical local and global shapes, and two comparison stimuli, matching the probe in local or global shape. They reported which comparison stimulus appeared more similar to the probe. In the “sad” group, participants chose the locally matching comparison more frequently than in the “happy” and “neutral” groups, suggesting that unpleasant mood can influence spatial preferences in haptic shape matching. Overall, participants tended to prefer global matches, indicating that under these specific conditions, global-level information may be relatively more prominent in touch.
Cavdan, M., Kapucu, A., Doerschner, K., & Drewing, K. (2025). Unpleasant mood is linked to local processing in haptics. i-Perception, 16(6), 1–14. https://doi.org/10.1177/20416695251403885

There is a growing scientific interest in material unpleasantness, yet the role of distinct physical parameters in perceptual and affective haptic experiences with liquids remains to be fully understood. To address this, we investigated how perceptual qualities of liquids relate to measurable physical properties and unpleasantness during active touch. We prepared 15 custom liquid samples using everyday materials. Rheological measurements showed that samples varied between physical viscosity 1⁢m⁢P⁢a⋅s and 45⁢P⁢a⋅s. Participants explored each sample using circular rubbing motions with their index fingers. A camera system tracked finger movements, and a force sensor revealed applied normal forces, pull-off force (PoF) and the coefficient of friction (CoF). We compared these physical properties with the perceptual dimensions from our earlier work: perceived viscosity and slipperiness. Perceived viscosity correlated strongly with both physical viscosity and PoF, but not with CoF. Conversely, perceived slipperiness was associated with CoF, but not PoF or physical viscosity, demonstrating distinct links between physics and perception of liquids. Interestingly, PoF but not CoF was significantly linked to unpleasantness, suggesting that PoF but not CoF is crucial for liquid unpleasantness. These findings advance our understanding of how distinct physical properties relate to perceptual and affective experiences of liquids.
Cavdan, M., Fehlberg, M., Bennewitz, R., & Drewing, K. (2025). Gooey stuff: the psychophysics of unpleasantness in response to touching liquids. Proceedings B, 292(2059), 20252244. https://doi.org/10.1098/rspb.2025.2244

Humans use distinct exploratory procedures (EPs) in active touch, which are typically specialized for materials with particular properties: for example, pressing for deformable objects such as cushions, or stroking to test a fabric's smoothness. Further, humans can use abstract visual priors for fine-tuning of exploratory movement parameters such as exploration direction. We here test the usage of visual priors in the planning of material-specific EPs, using real-life materials and a naturalistic visual virtual reality environment. We show that humans are better at selecting specialized EPs at initial touch when they have access to valid prior visual information on the material: They used specialized EP earlier, with higher probability, and explored materials for a shorter time. We conclude that visual prior information increases the efficiency of haptic explorations by anticipatory planning of appropriate movement schemes.
Michaela Jeschke & Knut Drewing (2025). Look first, feel faster: Prior visual information accelerates haptic material exploration. i-Perception, 16(5), 1–5. https://doi.org/10.1177/20416695251385816

The human role in human–swarm interaction (HSI) shifts from controller to supervisor, as robots become more autonomous and require efficient search strategies in complex visual environments. Previous research has shown that spatially uninformative brief cues enhance search performance in laboratory environments (namely, “pip-and-pop” effect). Here we examined if these effects can be effectively applicable in HSI. To this end, we conducted two experiments using small mobile robots (Thymio II) to investigate the impact of auditory, tactile, and audiotactile cues on visual search performance and timing judgments. In the first experiment, 20 participants identified a stopped robot among moving robots. The results showed that all cue conditions significantly reduced reaction times (RTs) compared to the no-cue condition, suggesting that brief spatially non-informative signals improve search performance by increasing sensory information accumulation speed. The second experiment involved 12 participants judging the duration of a robot’s stop after a tactile cue was presented or not. The findings indicate that tactile cues improve temporal sensitivity without affecting subjective duration judgments. These results highlight the potential of uni- and multisensory cues to enhance HSI performance by facilitating quicker and more accurate human responses, particularly in dynamic environments. The study extends the “pip-and-pop” effect to real-world scenarios, offering insights for designing HSI systems that allow users to interact with robotic swarms more naturally and efficiently.
Celebi, B., Kaduk, J., Cavdan, M., Hamann, H., & Drewing, K. (2025). Brief non-spatial signals facilitate visual search and temporal sensitivity in robot supervision. International Journal of Human-Computer Studies, 103643.

Interindividual differences in biophysical properties such as skin hydration and elasticity have been demonstrated to play a critical role in influencing various aspects of tactile perception. Here, we assess their role for interindividual variation of basic tactile abilities and the tactile distance adaptation aftereffect in a young adult sample. Tactile abilities were defined by tactile sensitivity in a monofilament detection task and spatial acuity in a grating orientation task. In the distance aftereffect, when a body area is repeatedly touched at two points separated by a given distance, subsequently presented smaller distances are perceived as smaller than on unadapted areas. Aftereffect magnitude describes the perceptual shift in a distance discrimination task following adaptation. We examine whether differences in skin hydration and elasticity at the finger pad are related to tactile abilities which in turn affect the magnitude of distance aftereffects. Results revealed that higher hydration and elasticity were related to increased tactile sensitivity and spatial acuity, but magnitude of distance aftereffects was independent from both skin properties and tactile abilities. While these results reemphasize the importance of healthy skin for tactile perception, they suggest individual differences in the magnitude of the distance aftereffect to be independent from peripheral skin properties.
M. Jeschke, E. Azañón and K. Drewing, "The Relationship Between Biophysical Skin Properties, Tactile Ability, and the Distance Adaptation-Aftereffect," 2025 IEEE World Haptics Conference (WHC), Suwon, Korea, Republic of, 2025, pp. 115-122. DOI: 10.1109/WHC64065.2025.11123197.

Friction between fingertip and surface is a key contribution to tactile perception during active exploration of materials. We explore the role of skin factors such as stratum corneum thickness and hydration, deformability, elasticity, or density of sweat glands and of Meissner corpuscles in friction and tactile perception. The skin parameters were determined non-invasively for the glabrous skin at the index finger pad of 60 participants. Sets of randomly rough plastic surfaces and of micro-structured fibrillar rubber surfaces were explored as model materials with well-defined parameterized textures. Friction varies greatly between participants, and this variation can be explained to 70% by skin factors for the randomly rough plastic surfaces. The predictability of friction by skin factors is much lower for micro-structured rubber surfaces with bendable fibrils, where 50% of variance is explained for the stiffest fibrils but only 20% for the most bendable fibrils. The participants’ age is the key predictor for their tactile sensitivity to perceive the fibrils, where age is negatively correlated to the density of Meissner corpuscles. The results suggest that stratum corneum hydration, skin deformability, and age are important factors for friction and perception in active tactile exploration of materials.
Infante, V. H., Fehlberg, M., Saikumar, S., Drewing, K., Meinke, M. C., & Bennewitz, R. (2025). The role of skin hydration, skin deformability, and age in tactile friction and perception of materials. Scientific Reports, 15(1), 9935. https://doi.org/10.1038/s41598-025-95052-4