Context and movement as factors influencing haptic illusions1

Abstract A haptic illusion is obtained when blindfolded Ss are required to trace along the raised contours of an illusion figure. In the present experiments it is asked whether haptic judgments of an illusion figure are influenced by the extent of the finger movements involved in inspection of the figure or by contextual tactile stimulation. The possible effects of these two variables have been unconfounded by requiring S to make finger movements over the same extent during inspection irrespective of whether the length being judged was presented alone or was adjacent to a longer contour. An illusion was obtained only when contextual tactile stimulation was present. The bearing of the data on some current theories of illusions is discussed.