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Treisman's feature integration theory postulates a first, preattentive stage stage of the feature integration theory. where the brain automatically gathers information about separate basic features, such as colour, shape, movement, in the visual field. This stage does not require focused attention.

A second stage of the theory requires focussed attention to combine locally features associated features to perceive whole objects. Hence, there are two kinds of visual search tasks: feature and conjunction search. Searches for targets defined by only one feature, such as colour, shape, or orientation. can be performed fast and pre-attentively and can "pop out" from the visual field during search.

In contrast, conjunction search, which require conscious attention and effort, is performed serially and more slowly than feature search to combine two or more features of a target. Treisman argues that colour, orientation, and intensity are features for which feature searches may be performed.