Feature integration theory

During this stage, different parts of the brain automatically gather information about basic features (colors, shape, movement) that are found in the visual field.

This top-down process, using prior knowledge to inform a current situation or decision, is paramount in either identifying or recognizing objects.

Due to damage in the parietal lobe, these people are unable to focus attention on individual objects.

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.

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".

[8] As previously mentioned, Balint's syndrome patients have provided support for the feature integration theory.

Particularly, Research participant R.M., who had Bálint's syndrome and 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.

If people use their prior knowledge or experience to perceive an object, they are less likely to make mistakes, or illusory conjunctions.

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.