Three layers of material are the maximum depth the human brain can process when judging how soft an object feels.
April 24, 2026
Original Paper
Heterogeneous Layered Structures Can Modulate Human Softness Perception
arXiv · 2604.20092
The Takeaway
Human touch perception is almost entirely dominated by the very outermost surface of whatever we are holding. Mechanical information from deeper layers contributes significantly to our sense of softness only until it reaches a depth of three layers. Our brains simplify complex and multi-layered objects into a shallow heuristic rather than calculating the whole structure. This means a material can feel luxurious and soft even if the core underneath it is incredibly rigid. Product designers can use this limit to create the illusion of high-quality materials by focusing only on the first few millimeters of contact.
From the 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