Understanding the interplay between surface roughness and material elasticity in haptic texture perception is important. In the real world, these characteristics do not occur isolated from one another, yet, the haptic perceptions of surface features and material properties are often investigated individually. This highlights the need for suitable stimulus material for haptic perceptual experiments. The present research details the manufacturing and validation of a database of stochastically-rough, elastic stimuli tailored for haptic perceptual experiments. The stimulus set comprises 49 3D-printed samples, offering a systematic variation in stochastic microscale roughness and material elasticity, replicating natural surface features without compromising experimental control. The surfaces were generated using an algorithm that produces randomly rough surfaces with well-defined spectral distributions, demonstrating fractal properties over a large range of length scales. Controlled variations in elasticity were implemented via variations of the printing material composition. Finally, we present preliminary perceptual data from two observers, illustrating the discriminability of the stimulus space for roughness and softness discrimination. This database aims to facilitate haptic research on material and texture perception, offering a controlled yet naturalistic set of stimuli to explore the intricate interplay between surface roughness and material elasticity in shaping haptic texture perception. ... Read more

We investigated whether surface texture (i.e., stochastic roughness) influences softness perception during direct touch interactions with elastic, textured stimuli. Using a Bayesian adaptive modeling approach and a 2AFC task, we evaluated participants' ability to discriminate the softness of stimuli that varied in both their stochastic surface roughness (Hurst exponent) and material elasticity. To explore potential interactions between these features, we conducted two discrimination experiments, testing stimuli from two distinct ranges of elasticity. All participants performed the task using pressing. Results show that softness discrimination was determined primarily by material elasticity, with no discernible influence of surface features. The findings suggest that humans effectively isolate elasticity-based information from smaller-scale surface topography or texture during direct pressing with the finger. ... Read more

Temporal binding refers to a systemic bias in the perceived time interval between two related events, most frequently voluntary motor actions and a subsequent sensory effect. An inevitable component of most instrumental motor actions is tactile feedback. Yet, the role of tactile feedback within this phenomenon remains largely unexplored. Here, we used local anesthesia of the index finger to temporarily inhibit incoming sensory input from the finger itself, while participants performed an interval-estimation task in which they estimated the delay between a voluntary motor action (button press) and a second sensory event (click sound). Results were compared to a control condition with intact sensation. While clear binding was present in both conditions, the effect was significantly enhanced when tactile feedback was temporarily removed via local anesthesia. The results are discussed in light of current debates surrounding the underlying mechanisms and function of this temporal bias. ... Read more