The kinesthetic fusion effect: Perceptual elimination of spatial discordance in the kinesthetic modality

Three experiments in intrasensory kinesthetic discordance are reported. The treatment required both arms to be outstretched in the midsagittal plane. In the absence of vision, a finger of one hand depressed a button that caused a probe to touch the other arm 12.7 cm closer to the body than the position of the finger. This difference was at first clearly sensed, but very rapidly the disparate positions were perceived to be identical: We have called this “the kinesthetic fusion effect.” It was also shown that a delay of up to 4 sec in probe onset after the finger depressed the button did not diminish the extent of fusion. The phenomenon gave rise to a predictable aftereffect, in which a probe directly opposite to the active finger was sensed to be farther away than the finger. The results were not due either to joint adaptation or to postural aftereffects.