Multisensory Research誌に、Oxford University 滞在時より執筆していたレビュー論文が刊行されました。
Material Dependency of Crossmodal Correspondences in Shitsukan (with a Focus on Food) Masashi Nakatani (Keio University) & Charles Spence (Oxford University) Multisensory Research (published online ahead of print 2026). https://doi.org/10.1163/22134808-bja10196
Heterogeneous Layered Structures Can Modulate Human Softness Perception Yuno Higuchi, Yosuke Iwashita, Yuji Ohgi, Masashi Nakatani https://arxiv.org/abs/2604.20092
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.
This study aims to clarify the effects of heterogeneous layered structures on human softness perception. Softness perception plays an essential role in evaluating products in daily life. Previous studies have uniformly varied the softness of the entire object. However, the real world contains numerous objects with heterogeneous softness, composed of multiple distinct layers or materials. Examples include fruits with a hard exterior and soft interior, or mattresses and pillows made from layered materials. How this heterogeneity affects softness perception when humans touch such objects remains poorly understood. Therefore, this study investigated human softness perception for objects exhibiting overall softness heterogeneity.
The aim of this study is to clarify how humans perceive softness when touching layered objects of non-uniform softness. Sixteen different tactile stimuli with varying layered structures were presented to participants, who were asked to provide subjective ranking evaluations. This paper focuses on the analysis of layered objects with varying softness at the fingertip contact area (T1–T4: hard contact area; T5–T8: soft contact area). Regression analysis revealed that the greater the number of hard layers present internally, the higher the perceived softness ranking increased significantly (i.e. objects were perceived as harder), indicating that differences in internal softness systematically influence human perception of softness. Furthermore, for particular layered structures, the perceived softness differed statistically significantly depending on the thickness of the soft layers when a soft layer was sandwiched between hard layers. Our results suggest that the distribution of hard and soft layers may exert a non-linear influence on human perception of softness.
Odera, M., Mori, M., & Nakatani, M. The Facial Carving Illusion: Natural Background can Modulate the Perception of Facial Carving. doi:10.24636/vision.37.4_153
The shading and shadow of the face are essential information forming the impression of a person’s face. This study presented the facial carving illusion: although the face in the foreground is the same, the facial carving is perceived to be more profound when the background is changed. We demonstrated several examples of the contrast and intensity of natural backgrounds changing the depth perception of the nose. Furthermore, this study investigated the effect of background image statistics on the perception of facial carving under controlled laboratory conditions. The experiment revealed that the perception of facial carving is most pronounced when a low mean and large variation of the intensity distribution characterize the background. These results suggest that a dark background and high contrast enhance the perception of facial carving. We concluded that the facial carving illusion includes one of the phenomena of brightness assimilation.
The SFC TOUCH LAB Final Presentation Session for the Fall Semester (2023 Academic Year) was held on January 25, 2024. Members who previously completed graduation projects in the Nakatani Laboratory also gathered as reviewers.