Visual search

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The more distractors there are the harder it is to locate the letter B in the array

The O has a distinctive feature compared to the X and appears to "Pop Out" of the array

The red X is also a feature singleton and attracts attention

Conjunctive Search, find the orange square

Visual Search is an extension of attention and vigilance. Visual search involves and active scan of the environment for particular features. Such as trying to locate certain brand of cereal at the grocery store or a picture of a friend in a group photograph. The process of Visual Search is made more difficult through the occurrence of distracters. Distracters are non target stimuli that divert attention away from the target stimulus. False Alarms occur when we mistake a distracter for our target stimulus. In daily life marketers often take advantage of this by creating product packaging that closely resembles a more well known brand.

The number of distracters has an effect on how difficult or taxing the visual search task is. The size of a given visual array is commonly referred to is referred to the display size. The display size effect is the degree which the size of the display size hinders the visual search process. Depending on the type of visual search the display size can vary greatly.

Contents

1 Types of search

1.1 Feature Search
1.2 Conjunction Search

2 Popular Search Theories
3 References

Types of search

Feature Search

Feature Search is the process of searching for distinctive feature. Such as color, size, orientation or shape. Feature searches can sometimes be easily conducted if the target stimulus has a distinctive feature compared to its distracters. The object often appears to “pop out” of the display. A unique feature which causes a stimulus which to “pop out” is referred to as a feature singleton. Feature singletons can also attract attention even if they are distracters.

Conjunction Search

Conjunction Search occurs when a single feature search is in sufficient. In a conjunction search each item in the visual array must be examined to determine if it is the target stimulus. The number of distracters can greatly increase the search time in a conjunction search.

Popular Search Theories

Feature Integration Theory
Similarity Theory
Guided Search Theory
Movement Filter Theory
Signal Detection Theory

References

Wolfe, J M (1998) Visual Search Originally Published in Attention, H. Pashler (Ed.), London, UK: University College London Press, [Fulltext]
J Theeuwes - Perception & Psychophysics, 1992 [Fulltext]
Treisman A (1991) Visual perception of features and objects(Annual Report, 15 Sep. 1990- 14 Sep. 1991). 53 Behavioral Sciences(AH)
Verghese, P (2001) Visual Search and Attention: a Signal Detection Theory approach. Neuron, 30 August 2001, vol. 31, no. 4, pp. 523-535(13).

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