Forearm vs whole-body sensations of self-motion: some results on the role of the sensorimotor context

Making a subject's visual surroundings move can give rise to sensations of self-motion, which can either be restricted to the arm or involve the whole body. The aim of the present study was to investigate the role played by the sensorimotor context in eliciting one or the other of these two types of illusory movement. Whether the type of sensation experienced by the subjects depended on their adoption of an actively maintained or relaxed posture was examined. Analysis showed subjects' posture was certainly one of the factors involved: a rigidly held position favoured the occurrence of whole body sensations of movement, whereas a relaxed attitude favoured occurrence of arm-restricted sensations. This postural factor alone does not, however, account for the variations recorded in our experiment which seem to be related to the stimulus parameters as well as to individual factors.