Experimental manipulation of head posture.

Variations in natural head position have been noted by previous workers to be associated with both dentoalveolar and craniofacial skeletal morphologic features. The determinants of cranial posture are as yet not known. Three experiments are described, dealing with the influence of (1) total nasal obstruction, (2) visual feedback deprivation, and (3) a combination of (1) and (2) on the posture of the cranium measured relative to a gravity-defined true vertical reference plane. The results indicate that total nasal obstruction results in all cases in an extended head position. Visual deprivation produces adaptation of a smaller magnitude and unpredictable direction. Combination of both experimentally induced conditions indicates a dominance of the respiratory adaptation in terms of postural response to these stimuli.