The framing effect with rectangular and trapezoidal surfaces: actual and pictorial surface slant, frame orientation, and viewing condition.

The perceived slant of a surface relative to the frontal plane can be reduced when the surface is viewed through a frame between the observer and the surface. Aspects of this framing effect were investigated in three experiments in which observers judged the orientations-in-depth of rectangular and trapezoidal surfaces which were matched for pictorial depth. In experiments 1 and 2, viewing was stationary-monocular. In experiment 1, a frontal rectangular frame was present or absent during viewing. The perceived slants of the surfaces were reduced in the presence of the frame; the reduction for the trapezoidal surface was greater, suggesting that conflict in stimulus information contributes to the phenomenon. In experiment 2, the rectangular frame was either frontal or slanted; in a third condition, a frame was trapezoidal and frontal. The conditions all elicited similar results, suggesting that the framing effect is not explained by pictorial perception of the display, or by assimilation of the surface orientation to the frame orientation. In experiment 3, viewing was moving-monocular to introduce motion parallax; the framing effect was reduced, being appreciable only for a trapezoidal surface. The results are related to other phenomena in which depth perception of points in space tends towards a frontal plane; this frontal-plane tendency is attributed to heavy experimental demands, mainly concerning impoverished, conflicting, and distracting information.