Stereograms appear to be composed entirely of
random dots. However, they contain separate images that a
viewer can “fuse” into a three-dimensional (3D) image by staring
at the dots while defocusing the eyes. An experiment was
performed to determine whether knowledge of the embedded
image affected the time required for subjects to fuse the images.
One group of subjects (group NV) received no information or
just verbal information about the shape of the embedded object.
A second group (group VV) received both verbal information
and visual information (specifically, a drawing of the object).
The experimenters measured how many seconds it took for the
subject to report that he or she saw the 3D image.