Fig. 2
From: Finding counterfeited banknotes: the roles of vision and touch
Haptic banknote interaction. Left: movement over the surface. Bending of the paper, fingers on two sides. Thumb on the front and index finger on reverse. The middle finger is sideways supporting the index finger. Middle: multiple contact areas. Thumb (and not index finger) is used to rub to and fro. It is assumed that typical movement ranges are about 20 mm. Right: various banknote properties are perceived with three fingertips (thumb, index and middle fingers). Illustrations by Wijntjes (2009)