Stages
According to Treisman, the first stage of the Feature Integration Theory is the preattentive stage. Perception occurs automatically, unconsciously, effortlessly, and early in the perceptual process. During this stage, the object is analyzed for details such as shape, color, orientation and movement, with each aspect being processed in different areas of the brain. The idea that features are automatically separated appears to be counterintuitive; however, we are not aware of this process because it occurs early in perceptual processing, before we become conscious of the object.
The second stage of the Feature Integration Theory is the focused attention stage, where the individual features of an object combine in order to perceive the whole object. In order to combine the individual features of an object, attention is required and selection of that object occurs within a "master map" of locations. The master map of locations contains all of the locations in which features have been detected, with each location in the master map having access to the multiple feature maps. When attention is focused at a particular location on the map, the features currently in that position are attended to and are stored in "object files". If the object is familiar, associations are made between the object and prior knowledge, which results in identification of that object. In support of this stage, researchers often refer to patients suffering from Balint's syndrome. Due to damage in the parietal lobe, these people are unable to focus attention on individual objects. When given stimuli that requires combining features, people suffering from Balint's syndrome are unable to focus attention long enough to combine the features, providing support for this stage of the theory.
Treisman distinguishes between two kinds of visual search tasks, "feature search" and "conjunction search". Feature searches can be performed fast and pre-attentively for targets defined by only one feature, such as color, shape, perceived direction of lighting, movement, or orientation. Features should "pop out" during search and should be able to form illusory conjunctions. Conversely, conjunction searches occur with the combination of two or more features and are identified serially. Conjunction search is much slower than feature search and requires conscious attention and effort. In multiple experiments, some referenced in this article, Treisman concluded that color, orientation, and intensity are features for which feature searches may be performed.
As a reaction to the Feature Integration Theory, Wolfe (1994) proposed the Guided Search Model 2.0. According to this model, attention is directed to an object or location through a preattentive process. The preattentive process, as Wolfe explains, directs attention in both a bottom-up and top-down way. Information acquired through both bottom-up and top-down processing is ranked according to priority. The priority ranking guides visual search and makes the search more efficient. Whether the Guided Search Model 2.0 or the Feature Integration Theory are "correct" theory of visual search is still a hotly debated topic.
Read more about this topic: Feature Integration Theory
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