Resolving perceptual conflicts: the cognitive mechanism of spatial orientation.

The cognitive mechanisms of spatial orientation were studied in an experiment varying different perceptual cues systematically: the retinal, the visual background, the vestibular, and the somatosensory information. Verbal descriptions of visually presented arrays were required under different head positions (straight/tilt) and under different gravity conditions (1 G/micro G). Results for two subjects clearly show that different coordinate systems are used under the two gravity conditions. Under 1 G it is the gravitational vertical which is chosen for primary reference, whereas under microgravity retinal information is primary. Conflicts between competing pieces of sensory information are solved by weighting the perceptual cues differently. The finding that consistent assignment can be made immediately after first exposure to weightlessness indicates that mental representations of space can be used independently of perceptual input parameters.