Monday, July 11, 2011
Feature Integration Theory
The Feature Integration Theory was originally proposed by Anne Treisman and Garry Gelade. The theory describes the processing of an object by the visual system and occurs in two separate stages. The first stage is known as the preattentive stage because it does not depend on any attention whatsoever. This stage occurs so quickly that we are unaware of it while an object is broken down into features such as color, orientation, and location. The second stage in the Feature Integration Theory is called the focused attention stage and that is because it does depend on attention unlike the preattentive stage. During this stage the features are recombined so that we perceive the whole object rather than just its individual features. Treisman links together the process of binding that occurs in the focused attention stage to physiology by noticing that an object causes activity in both the "what" and the "where" streams of the cortex. The activity in the "what" stream would include information about features such as form and color. The activity that takes place in the "where" stream would include information about the location and the motion. Treisman said that attention is the "glue" that combines the information from the "what" and the "where" steams and causes us to perceive all of the features of an object as being combined together at a specific location. When we pay attention to an object all of its features are combined at that location and we then perceive the object. The process is simple because we are focusing on a single object at a fixed location. Although things can become more complicated when we introduce multiple objects occurring in the same environment. However, when we consider multiple objects, many features are involved and these features exist at many different locations. The task of the perceptual system is to associate each of these features with the object to which it belongs. As a result, feature integration theory proposes that in order for this to occur, we need to focus our attention on each object in turn. It is once we attend to a specific location, the features at that location are bound together and are then associated with the object at that location.