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==Stages==
According to Treisman, the first stage of the feature integration theory is the preattentive stage. During this stage, different parts of the brain automatically gather information about basic features (colors, shape, movement) that are found in the visual field. The idea that features are automatically separated appears to be counterintuitive;. howeverHowever, 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 thea subject combines individual features of an object combine in order to perceive the whole object. In order to combine theCombining individual features of an object, requires attention is required, and selection ofselecting 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. Given a stimulus 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 feature integration theory|thumb|300px|The stages of feature integration theory]]
==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 toTo 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 where 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 feature 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 feature integration theory. 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 toTo 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.
By Treisman, Anne; Souther, Janet. Journal of Experimental Psychology: Human Perception and Performance, Vol 12(1), Feb 1986, 3-17.</ref> Treisman maintained that prior-knowledge played an important role in proper perception. Normally, bottom-up processing is used for identifying novel objects; but, once we recall prior knowledge, top-down processing is used. This explains why people are good at identifying familiar objects rather than unfamiliar.
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