Feature integration theory: Difference between revisions

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==Stages==

According to Treisman, the first stage of the Featurefeature Integrationintegration Theorytheory 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 Featurefeature Integrationintegration Theorytheory 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.

[[File:FITstages.png|alt=The stages of Featurefeature Integrationintegration Theory.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 (geometry)|orientation]], and [[intensity (disambiguation)|intensity]] are features for which feature searches may be performed.

As a reaction to the Featurefeature Integrationintegration Theorytheory, 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 Featurefeature Integrationintegration Theorytheory are "correct" theory of visual search is still a hotly debated topic.

==Experiments==

<!-- Deleted image removed: [[File:fourshapesexp.png|thumb|alt=An example of four colored shapes and two black letters.|An example of the stimuli found in Treisman et al. (1982).]] -->In order to test the notion that attention plays a vital role in visual perception, Treisman and Schmidt (1982) designed an experiment to show that features may exist independently of one another early in processing. Participants were shown a picture involving four objects hidden by two black numbers. The display was flashed for one-fifth of a second followed by a random-dot masking field that appeared on screen to eliminate “any residual perception that might remain after the stimuli were turned off”.<ref>Cognitive Psychology, E. Bruce Goldstein, P 105</ref> Participants were to report the black numbers they saw at each ___location when the shapes had previously been. The results of this experiment verified Treisman and Schmidt's hypothesis. In 18% of trials, participants reported seeing shapes “made up of a combination of features from two different stimuli”,<ref>Cognitive Psychology, E. Bruce Goldstein, P 105</ref> even when the stimuli had great differences; this is often referred to as an [[illusory conjunction]]. Specifically, illusory conjunctions occur in various situations. For example, you may identify a passing person wearing a red shirt and yellow hat and very quickly transform him or her into one wearing a yellow shirt and red hat. The Featurefeature integration theory provides explanation for illusory conjunctions; because features exist independently of one another during early processing and are not associated with a specific object, they can easily be incorrectly combined both in laboratory settings, as well as in real life situations.<ref>Treisman, A. Cognitive Psychology 12, 97-136 (1980)</ref>

As previously mentioned, Balint's syndrome patients have provided support for the Featurefeature Integrationintegration Theorytheory. Particularly, Research participant R.M., a [[Bálint's syndrome]] sufferer who was unable to focus attention on individual objects, experiences illusory conjunctions when presented with simple stimuli such as a "blue O" or a "red T." In 23% of trials, even when able to view the stimulus for as long as 10 seconds, R.M. reported seeing a "red O" or a "blue T".<ref>Friedman-Hill et al., 1995; Robertson et al., 1997.</ref> This finding is in accordance with feature integration theory's prediction of how one with a lack of focused attention would erroneously combine features.

[[File:treismanshapes.png|thumb|alt=The stimuli resembling a carrot, lake and tire, respectively.|The stimuli resembling a carrot, lake and tire, respectively. Treisman et al.(1986).]]If people use their prior knowledge or experience to perceive an object, they are less likely to make mistakes, or illusory conjunctions. In order to explain this phenomenon, Treisman and Souther (1986) conducted an experiment in which they presented three shapes to participants where illusory conjunctions could exist. Surprisingly, when she told participants that they were being shown a carrot, lake, and tire (in place of the orange triangle, blue oval, and black circle, respectively), illusory conjunctions did not exist.<ref>Illusory words: The roles of attention and of top–down constraints in conjoining letters to form words.