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

Feature integration theory arose to explain different kinds of search latency
functions and illusory conjunctions. It assumes that vision begins with a first, noncognitive
stage of feature detection in which separate maps for a small number of
basic features, such as colour, orientation, size, or movement, record the presence
and location of detected properties. If a target is uniquely defined in terms of possessing
one of these features, then it will be the only source of activity in that feature
map and will therefore pop out, explaining some of the visual search results.
A second stage of processing belongs properly to visual cognition. In this stage,
a spotlight of attention is volitionally directed to a particular spot on a master map
of locations. This attentional spotlight enables the visual system to integrate features
by bringing into register different feature maps at the location of interest.
Different features present at that location can be conjoined together in a temporary
object representation called an object file (Kahneman, Treisman, & Gibbs, 1992;
Treisman, Kahneman, & Burkell, 1983). Thus in feature integration theory, searching
for objects defined by unique combinations of features requires a serial scan of
the attentional spotlight from location to location, explaining the nature of search
latency functions for such objects. This stage of processing also explains illusory
conjunctions, which usually occur when the attentional processing is divided,
impairing the ability of correctly combining features into object files.
A third stage of processing belongs to higher-order cognition. It involves using
information about detected objects (i.e., features united in object files) as links to
general knowledge of the world.
Conscious perception depends on temporary object representations in which the
different features are collected from the dimensional modules and inter-related,
then matched to stored descriptions in a long-term visual memory to allow recognition.
(Treisman, 1988, p. 204)
Another proposal that relies on the notion of visual cognition concerns visual routines
(Ullman, 1984). Ullman (1984) noted that the perception of spatial relations
is central to visual processing. However, many spatial relations cannot be directly
delivered by the parallel, data-driven processes postulated by natural computationalists,
because these relations are not defined over entire scenes, but are instead
defined over particular entities in scenes (i.e., objects or their parts). Furthermore,
many of these relations must be computed using serial processing of the sort that is
not proposed to be part of the networks that propagate natural constraints.
For example, consider determining whether some point x is inside a contour y.
Ullman (1984) pointed out that there is little known about how the relation inside
(x, y) is actually computed, and argued that it most likely requires serial processing
in which activation begins at x, spreading outward. It can be concluded that
x is inside y if the spreading activation is contained by y. Furthermore, before
inside (x, y) can be computed, the two entities, x and y, have to be individuated and
Seeing and Visualizing 381