Mind, Body, World- Foundations of Cognitive Science, 2013a

A related phenomenon is inattentional blindness, in which visual information that
should be obvious is not noticed because attention is not directed to it (even though
the gaze is!). In one famous experiment (Simons & Chabris, 1999), subjects watched
a video of a basketball game and were instructed to count the number of times that
the teams changed possession of the ball. In the midst of the game a person dressed
in a gorilla suit walked out onto the court and danced a jig. Amazingly, most subjects
failed to notice this highly visible event because they were paying attention to the ball.
If the visual system collects fragments of visual information a glance at a time,
then our visual experience further suggests that these different fragments are
“stitched together” to create a stable panorama. In order for this to occur, the fragments
have to be inserted in the correct place, presumably by identifying components
of the fragment (in terms of visible properties) in such a way that it can be
asserted that “object x in one location in a glimpse collected at time t + 1 is the
same thing as object y in a different location in a glimpse collected at an earlier
time t.” This involves computing correspondence, or tracking the identities of
objects over time or space, a problem central to the study of binocular vision (Marr,
Palm, & Poggio, 1978; Marr & Poggio, 1979) and motion perception (Dawson, 1991;
Dawson & Pylyshyn, 1988; Ullman, 1978, 1979).
However, the computing of correspondence is a classic problem of underdetermination.
If there are N different elements in two different views of a scene, then
there are at least N! ways to match the identities of elements across the views. This
problem cannot be solved by image matching—basing the matches on the appearance
or description of elements in the different views—because the dynamic nature
of the world, coupled with the loss of information about it when it is projected onto
the eyes, means that there are usually radical changes to an object’s proximal stimulus
over even brief periods of time.
How do we know which description uniquely applies to a particular individual
and, what’s more important, how do we know which description will be unique
at some time in the future when we will need to find the representation of that
particular token again in order to add some newly noticed information to it?
(Pylyshyn, 2007, p. 12)
To summarize, visual perception is intrinsically underdetermined because of the
poverty of the visual stimulus. If the goal of vision is to construct representations
of the distal world, then proximal stimuli do not themselves contain enough information
to accomplish this goal. In principle, an infinite number of distal scenes
could be the cause of a single proximal stimulus. “And yet we do not perceive a
range of possible alternative worlds when we look out at a scene. We invariably see
a single unique layout. Somehow the visual system manages to select one of the
myriad logical possibilities” (Pylyshyn, 2003b, p. 94). Furthermore, the interpretation
selected by the visual system seems—from our success in interacting with the
Seeing and Visualizing 367