Proffit line length experiments

vert/horiz line length judgements
when does vertical height match horiz separation
systematic vertical overestimation

orig 1999 experiment
overestimation more with reality than pictures
perceived physical size of projection on surface
(not apparent represented size)
2x greater viewing large objects than small pictures
even if identical visual angles

is this about 3D vs 2D, or immersion, or what? 

  Yang, T. L., Dixon, M. W., &  Proffitt, D. R. (1999). Seeing big things:  Overestimation of
   heights is greater for real objects than for objects in pictures. Perception. 28, 445-467.