page_title: Visual search
section_title: Visual orienting and attention
hierarchical_section_title: Visual search / Visual orienting and attention
caption_attribution_description: English: Foveated tombstones
context_page_description: 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 among other objects or features. 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 amongst a set of red circles.
context_section_description: One obvious way to select visual information is to turn towards it, also known as visual orienting. This may be a movement of the head and/or eyes towards the visual stimulus, called a saccade. Through a process called foveation, the eyes fixate on the object of interest, making the image of the visual stimulus fall on the fovea of the eye, the central part of the retina with the sharpest visual acuity.
  There are two types of orienting:
  Exogenous orienting is the involuntary and automatic movement that occurs to direct one's visual attention toward a sudden disruption in his peripheral vision field. Attention is therefore externally guided by a stimulus, resulting in a reflexive saccade.
  Endogenous orienting is the voluntary movement that occurs in order for one to focus visual attention on a goal-driven stimulus. Thus, the focus of attention of the perceiver can be manipulated by the demands of a task. A scanning saccade is triggered endogenously for the purpose of exploring the visual environment.
  Visual search relies primarily on endogenous orienting because participants have the goal to detect the presence or absence of a specific target object in an array of other distracting objects.
  Early research suggested that attention could be covertly (without eye movement) shifted to peripheral stimuli, but later studies found that small saccades (microsaccades) occur during these tasks, and that these eye movements are frequently directed towards the attended locations (whether or not there are visible stimuli). These findings indicate that attention plays a critical role in understanding visual search.
  Subsequently, competing theories of attention have come to dominate visual search discourse. The environment contains a vast amount of information. We are limited in the amount of information we are able to process at any one time, so it is therefore necessary that we have mechanisms by which extraneous stimuli can be filtered and only relevant information attended to. In the study of attention, psychologists distinguish between preattentitive and attentional processes. Preattentive processes are evenly distributed across all input signals, forming a kind of "low-level" attention. Attentional processes are more selective and can only be applied to specific preattentive input. A large part of the current debate in visual search theory centres on selective attention and what the visual system is capable of achieving without focal attention.
caption: A photograph that simulates foveation
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