Any number of drawings
are ambiguous, where a single drawing has two or more different
interpretations. A famous example is the Necker cube shown
off to the right. The Necker cube can either seem as if
the upper square is the front face, or the lower square
is the front face.
The ambiguity arises in part because our
visual system evolved to make sense of a 3-dimensional world,
but uses 2-D optical projections to get the job done. Many
of the mechanisms we employ to extract depth from an image
can be triggered by a flat 2-dimensional display that has
no depth. In this case, a bunch of lines on a computer screen
appears as a 3-D cube.
A brief presentation of an unambiguous
stimulus can influence how an ambiguous stimulus is later
interpreted. There also seems to be a fatiguing effect,
where the perceived images seem to switch spontaneously
from one interpretation to another, sometimes over decreasing
time intervals. |