Influence of head posture on perception of chin projection.

STRUCTURED ABSTRACTAIM: The aim of the present study was to assess the effect of head posture (extended or flexed) on the perception of chin prominence, by a panel of laypersons.DESIGN: Random-trial, method of adjustment.SETTING: Orthodontic Department, Athens University Dental School.MATERIAL AND METHODS: A single profile photograph was warped to produce 30 frames depicting a gradual change from a posterior to an anterior chin position. Using computer software, these frames could be displayed sequentially, giving the impression that the chin was moving forwards or backwards. Adjacent to this user-adjustable image, one of the intermediary frames was displayed, as a target image, either in the same orientation or rotated (extended or flexed by 10°). 39 laypersons used the keyboard and moved the chin until the face seemed to them identical to the reference image. The selected image frame was noted.RESULTS: Judges could estimate facial morphology without systematic error when the head of the reference image was at the same orientation (horizontal) or rotated downwards. However, when the reference image was rotated upwards, chin protrusion was overestimated.CONCLUSION: Perception of facial profile form may be different when the head is extended than when it is flexed or in a horizontal position.