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 either with or without eye movements. Common examples include trying to locate a certain brand of cereal at the grocery store or a friend in a crowd (e.g. Where's Waldo?). The scientific study of visual search typically makes use of simple, well-defined search items such as oriented bars or colored letters. The cognitive architecture of the visual system is then assessed by establishing which factors affect the amount of time taken by the observer to indicate whether a search target is present or absent. One of the most common factors affecting such measures of reaction time (RT) relates to the number of distractors present in the visual search task. An increase in the number of distractors often leads to an increase in search RT and is thus also related to an increase in difficulty of the task (See Fig 1). The measure of the involvement of attention in the search task is often manifested as a slope of the response time function over the display size, or number of distractors (RT slope).