Tactile recognition of raised characters: A parametric study

The accuracy of tactile recognition of raised characters was studied as a function of five variables: (1) height of the upper surfaces of the characters relative to the surrounding base, (2) character set (uppercase roman and braille), (3) spatial extent of the characters (two sizes), (4) mode of touch (static and moving), (5) contact force (two values). All stimuli were felt with the distal pad of the right index finger. The experiment was a repeated-measures design with six subjects. There were significant main effects of all variables except contact force. Of the tests for interaction, only height × mode was significant; the indication is that, whereas moving the finger permits a considerable improvement in performance over static touch for very shallow characters, moving the finger improves performance only slightly over static touch for characters of much greater height.