Tactile adaptation transfers between distance and continuous size

Tactile spatial perceived distance between two touches is larger on sensitive skin regions. While such distortions are substantial for the perception of distance between two distinct touches, they are significantly reduced when participants estimate the size of a single continuous object touching the skin. Here, we examine whether some of the mechanisms involved in processing the distance between two touches are shared with and influence those underlying the perception of continuous objects, leveraging adaptation aftereffects. In experiment 1, participants adapted to specific distances between two points, and we assessed the effect on both point-based and continuous object perception. Experiment 2 tested whether adaptation to continuous objects influenced distance perception similarly. Results showed that two-point adaptation induced aftereffects of similar magnitude for both two-point and object stimuli, while adaptation to continuous objects produced larger aftereffects specifically for object stimuli. These results indicate that aftereffects generated by simple touches generalize across different stimulation types, whereas those induced by continuous objects remain stimulus specific. Therefore, it is reasonable to assert that the distance perception of two touches arises at early stages of tactile processing that subsequently affects perception at later stages. Whereas distance perception of continuous objects is processed at later stages and is object specific.