Visual search paradigm

Visual search is a psychophysical paradigm that is often to study visual attention by asking subjects to find one (or more) specific stimulus (target) among an array of stimuli. Non-target items (distractors) are often similar to the target stimulus excepet in a single dimension (e.g., color or orientation). In simple search, a particular feature of the target differs from all distractors (e.g., searching for a red vertical bar among green vertical bars or searching for a red vertical bar among red horiontal bar).

In conjunction search, all features of the target are present in some of the distractors (e.g., seaching for a red vertical bar among green vertical bars and red horizontal bars). An interesting property of visual search is that the search time for simple search is often fast and does not depend on the number of items (array size) whereas for conjunction search, reaction time linearly increases with array size. See Visual search