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==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 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>
Research participant R.M., a [[Bálint's syndrome]] sufferer who is unable to focus attention on individual objects, experiences illusory conjunctions when presented with simple stimuli such as a "blue O" or a "red T." For 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.▼
▲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
[[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).]]However, if people use their knowledge or experience to perceive an object, they are less likely to make mistakes. Treisman did another experiment to explain this phenomenon – she presented three shapes to participants and illusory conjunctions persisted. 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 disappeared.<ref>Illusory words: The roles of attention and of top–down constraints in conjoining letters to form words.▼
▲[[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).]]
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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