“…The ability of the human organism to respond adaptively to optical transformations such as displacement or rotation of the visual field has been known since the end of the last century (e.g., Helmholtz, 1925;Stratton, 1896). Almost two decades of intense research, from about 1955 to 1975, revealed the bewildering complexity of this adaptive response, including postural adjustments, simple motor-response learning, and perceptual changes in vision, proprioception, and audition (for a review, see Welch, 1978).…”