Visual search  Visual search is a type of perceptual task requiring attention that typically involves an active scan of the visual environment for a particular object or feature (the target) among other objects or features (the distractors). Visual search can take place with or without eye movements. The ability to consciously locate an object or target amongst a complex array of stimuli has been extensively studied over the past 40 years. Practical examples of using visual search can be seen in everyday life, such as when one is picking out a product on a supermarket shelf, when animals are searching for food among piles of leaves, when trying to find a friend in a large crowd of people, or simply when playing visual search games such as "Where's Wally?" Much previous literature on visual search used reaction time in order to measure the time it takes to detect the target amongst its distractors. An example of this could be a green square (the target) amongst a set of red circles (the distractors). However, reaction time measurements do not always distinguish between the role of attention and other factors: a long reaction time might be the result of difficulty directing attention to the target, or slowed decision-making processes or slowed motor responses after attention is already directed to the target and the target has already been detected. Many visual search paradigms have therefore used eye movement as a means to measure the degree of attention given to stimuli. However, eye movements can move independently of attention, and therefore eye movement measures do not completely capture the role of attention. Feature search (also known as "disjunctive" or "efficient" search) is a visual search process that focuses on identifying a previously requested target amongst distractors that differ from the target by a unique visual feature such as color, shape, orientation, or size. An example of a feature search task is asking a participant to identify a white square (target) surrounded by black squares (distractors). In this type of visual search, the distractors are characterized by the same visual features. The efficiency of feature search in regards to reaction time(RT) and accuracy depends on the "pop out" effect, bottom-up processing, and parallel processing. However, the efficiency of feature search is unaffected by the number of distractors present. The "pop out" effect is an element of feature search that characterizes the target's ability to stand out from surrounding distractors due to its unique feature. Bottom-up processing, which is the processing of information that depends on input from the environment, explains how one utilizes feature detectors to process characteristics of the stimuli and differentiate a target from its distractors.