Explain Triesman's feature integration theory and give an example of a study that illustrates it.

Explain Triesman's feature integration theory and give an example of a study that illustrates it.

This theory suggests that when perceiving a stimulus, features are "registered early, automatically, and in parallel, while objects are identified separately" and at a later stage in processing. The theory has been one of the most influential psychological models of human visual attention. It was developed by Triesman on the basis of Broadbent's theory. 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 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 1982 Triesman and Schmidt 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". 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.
The great support for this theory is given by patients with Balint's syndrome, who are unable to to perceive the visual field as a whole (simultanagnosia), have difficulty in fixating the eyes (oculomotor apraxia), and are unable to move the hand to a specific object by using vision (optic ataxia).

The Treisman and Schmidt study also showed that even when two stimuli had obvious differences participants often reported seeing a stimulus where features of two different stimuli are combined into one. This is called illusory conjunction and is easily understood by an example when someone seeing a person with a red shirt and a green bag, might think of the bag as red and the shirt as green. This supports the feature integration theory which claims that features exist independently of each other and of objects, therefore they can be misleadingly combined to create illusory conjunctions.