That is, upon detecting a change in {TAIL ~ viewpoint} , {HEAD ~ the image} of the person changes 
That is , upon detecting a change in { TAIL ~ viewpoint } , { HEAD ~ the image } of the person changes
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH