In a motion perspective 
experiment, observers viewing 
moving shadows of paint 
droplets on a screen were able 
to perceive that the plane was 
slanted. 
 
    Eleanor and James Gibson 
and their associates performed 
experiments that at least 
partially bear out his 
contention. In one experiment, 
they spattered paint on a 
transparent sheet and, as can 
be seen in the animation 
shown here, slanted the sheet 
away from the vertical plane. A 
small light was used to cast 
shadows of the paint droplets 
on a translucent vertical 
screen in front of the 
transparent sheet. When the 
sheet was moved back and 
forth, the shadows of the 
droplets moved back and forth 
over the screen. Because of the 
slant of the sheet, a gradient of 
motion velocity was created 
from the bottom to the top of 
the screen, with the shadows 
at the top of the screen moving 
more rapidly than those at the 
bottom. The investigators 
reasoned that, since the screen 
was actually vertical and flat, 
subjects looking at the moving 
shadows of the droplets on the 
screen would be able to 
perceive the slant of the sheet 
correctly only if motion 
perspective is a source of depth 
information.