Haptic after-effect of successively touched curved surfaces

A flat surface is more often judged to be convex after the touching of a co ncave surface than after the touching of a convex surface. This haptic afte r-effect increases with the time of contact with the curved surface till it saturates, and it decreases with the time-lapse between the touching of th e first surface and the next one. In this paper, the haptic after-effect of two successively touched spherically curved surfaces is investigated. It i s found that both surfaces contribute to the after-effect, but the after-ef fect is not additive. The time course of the after-effect of two successive surfaces can be described by a first-order integrator with a single time c onstant of about 7 s and an amplitude equal to the difference between the s aturation levels of the after-effects of the two surfaces when measured in isolation. The new saturation level is therefore equal to that of the after -effect of the most recently touched surface. (C) 2001 Elsevier Science B.V . All rights reserved.