The role of elevation cue in pictorial depth space

It is widely accepted that the relative height of objects is an important cue of depth perception in pictorial displays. However, this phenomenon has never been investigated experimentally. The present study was designed to systematically test the elevation cue in various pictorial contexts. An experiment was conducted to examine the role of relative elevation of two identical 1.43 deg*1.43 deg squares presented with different orientations to one another (at 45deg and 225deg) and at different separations from one another (1.43 deg and 2.86 deg) in the perception of depth. In addition, the two squares were presented at seven different heights, on the left and on the right of the monitor and within different pictorial contexts (eg a gradient on the floor only; gradients on the floor limited by a wall at a distance; gradients both on the floor and ceiling limited by a wall at a distance; and a single line of the horizon), together with a control con- dition without any background structure. As expected, the results show floor gradient effects in the perception of depth as a function of relative elevation. In addition, the wall and the ceiling gradient significantly change this effect. The depth effect is inverted, with squares in higher positions being perceived closer.