Heterogeneous Layered Structures Can Modulate Human Softness Perception
Yuno Higuchi, Yosuke Iwashita, Yuji Ohgi, Masashi Nakatani
TLDR
This study shows that human perception of softness in layered objects is influenced by both overall stiffness and the depth of soft layers, especially the outermost one.
Key contributions
- Outermost layer stiffness most significantly impacts perceived softness in layered objects.
- Perceived softness increases with more soft subsurface layers, but this effect diminishes with depth.
- Layers 2 and 3 significantly influence softness perception, while deeper layers (e.g., Layer 4) do not.
Why it matters
This paper advances our understanding of human haptic perception beyond homogeneous objects. It provides crucial insights for designing materials and interfaces that aim to evoke specific softness sensations, impacting fields from product design to virtual reality.
Original Abstract
Human softness perception in haptics has mainly been studied using mechanically homogeneous objects, despite the fact that many real-world objects exhibit heterogeneous layered structures with nonuniform stiffness. This study examined how layered heterogeneity modulates haptic softness perception. Sixteen lattice-structured stimuli were fabricated by 3D printing, with the stiffness of the upper four layers systematically varied while the bottom two layers remained fixed. Twenty-two participants evaluated the softness of the stimuli in a psychophysical task, and compression tests were conducted to quantify their mechanical properties. Perceived softness was significantly predicted by displacement under load, however, perceptual ranking did not fully coincide with the physical ranking. Linear mixed-effects analyses showed that the softness of the outermost layer had the greatest impact on the perceived softness. Perceived softness also increased as the number of soft subsurface layers increased, although this contribution decreased with depth. Layers 2 and 3 showed significant effects, whereas Layer 4 did not. These findings suggest that haptic softness perception depends not only on the overall stiffness but also on the depth-dependent distribution of compliance within layered structures.
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