A kinesthetic spatial aftereffect with pronation of the forearm

Kinaesthetic spatial aftereffects from one and two wrists: a problem for neural enhancement theory

An experiment is described which investigated a kinaesthetic spatial aftereffect related to the wrist joint. In one condition 24 Ss made a kinaesthetic judgement of ‘straightahead’ using rotation of only one wrist. In a second condition 24 different Ss made the same spatial judgement using both wrists at once. Kinaesthetic aftereffects were measured in both conditions and it was found that the mean aftereffect per wrist in the two-handed task was about three times the size of that found in the single-handed one, a difference significant at the p < 0 01 level. It is argued that this finding constitutes a difficulty for Over's (1971) ‘neural enhancement’ theory which seeks to explain kinaesthetic spatial aftereffects solely in terms of the neural events underlying the perception of individual joint positions.