Normal surroundings appear curved when viewed through wedge prism eyeglasses. But prolonged viewing of uniformly curved lines makes them appear less curved. An environment specially patterned to prevent the appearance of curvature when viewed through a prism made possible the demonstration of change in apparent curvature wholly dependent upon the visual feedback accompanying self-produced movement of the prism-wearer.

Comparisons were made between the compensations produced by sagittal and by transverse arm motions under equivalent conditions of exposure and test. Effects of exposure with sagittal motion generalize more to transverse than vice versa. The differences may be related to the greater precision of body midline judgments with saggital motion.

10 Ss pointed at concealed auditory targets while listening through a pseudophone which produced 20" functional rotation of the interaural axis. After short exposures listening to a sound source held in one hand while moving that hand about, large and significant corrective shifts in pointing were measured.Accurate spatially-oriented behavior requires the maintenance of a set of known and stable relationships between the observer and his perceptual world. W e have found it productive to perturb these relationships in order to study the nature and extent of the adaptation which occurs. Our recent work has emphasized auditory spatial orientation or auditorily guided motor behavior. W e have shown that ability to discriminate dichotic time differences deteriorates markedly during exposures to dichotic white noise (Freedman & Pfaff, 1962;Freedman & Zacks, 1964). Also under appropriate conditions, Ss tend to compensate (or correct) for pseudophonic displacements of the apparent locations of auditory stimuli (Freedman & Stampfer, 1964). All of these experiments required whole-body movement during the exposure period which is difficult to limit and control. It seemed desirable to have comparable experimencs involving more circumscribed sensorimotor systems. A procedure was therefore devised to study hand-ear coordination, i.e., reaching and pointing at a concealed auditory carget.Preliminary studies indicated that Ss would compensate significantly for 20" rotation of the interaural axis in hand-ear coordination if they simply listened while moving a hand-held sound source back and forth across the front of their bodies for a few minutes (Freedman & Gardos, 1965). Unfortunately, as in many sensorimotor adaptation studies, the intersubject variability was high; also we feared that response stereotypy had confounded the results. The present paper describes a replication of that work with improved procedures and controls.The experimenu were conducted in a small room ( 1 6 ft. X 7 ft. X 9 ft. high) whose walls and ceiling were covered with acoustic tile. S sat comfortably on a stool at

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Ss walked about out of doors wearing laterally displacing prisms, and sound~attenuatinlJ muffs. Errors occurred in an auditory localization task during exposure to visual displacement. With continued exposure these errors tended to disappear after about lBO min. The errors disappeared earlier when muffs were not worn.