Texture perception at the foot sole: comparison between walking, sitting, and to the hand.

We frequently interact with textured surfaces with both our feet and hands. Like texture's importance for grasping, texture perception via the foot sole might provide important signals about the stability of a surface, aiding in maintaining balance. However, how textures are perceived by the foot, and especially under the high forces experienced during walking, is unknown. The current study builds on extensive research investigating texture perception at the hand by presenting everyday textures to the foot while stepping onto them, exploring them with the foot while sitting, and exploring them with the hand. Participants rated each texture along three perceptual dimensions: roughness, hardness, and stickiness. Participants also rated how stable their posture felt when standing upon each texture. Results show that perceptual ratings of each textural dimension were highly correlated across conditions. Hardness exhibited the greatest consistency and stickiness the weakest. Moreover, correlations between stepping and exploration with the foot were lower than those between exploration with the foot and exploration with the hand, suggesting that mode of interaction (high vs. low force) impacts perception more than body region used (foot vs. hand). On an individual level, correlations between conditions were higher than those between participants, suggesting that differences are greater between individuals than between mode of interaction or body region. When investigating the relationship to perceived stability, only hardness contributed significantly, with harder surfaces rated as more stable. Overall, tactile perception appears consistent across body regions and interaction modes, although differences in perception are greater during walking. We frequently interact with textured surfaces using our feet, but little is known about how textures on the foot sole are perceived as compared with the hand. Here, we show that roughness, hardness, and stickiness ratings are broadly consistent when stepping on textures, exploring them with the foot sole, or with the hand. Hardness also contributes to perceived stability.