Orientation categories used in guidance of attention in visual search can differ in strength

Garry Kong*, David Alais, Erik Van der Burg

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


We investigated orientation categories in the guidance of attention in visual search. In the first two experiments, participants had a limited amount of time to find a target line among distractors lines. We systematically varied the orientation of the target and the angular difference between the target and distractors. We find vertical, horizontal, and 45° targets require the least target/distractor angular difference to be found reliably and that the rate at which increases in target/distractor difference decrease search difficulty to be independent of target identity. Unexpectedly, even when the angular difference between the target and distractors was large, search performance was never optimal when the target orientation was 45°. A third experiment investigates this unexpected finding by correlating target/distractor difference and error rate with performance on tasks that measure a specific perceptual or cognitive ability. We find that the elevated error rate is correlated with performance on stimulus recognition and identification tasks, while the amount of target/distractor difference needed to detect the target reliably is correlated with performance on a stimulus reproduction task. We conclude that the target/distractor difference reveals the number of orientation categories in visual search, and, accordingly, that there are four such categories: two strong ones centred on 0° and 90° and two weak ones centred on 45° and 135°.

Original languageEnglish
Pages (from-to)2246-2256
Number of pages11
JournalAttention, Perception, and Psychophysics
Issue number8
Publication statusPublished - 2017 Nov 1
Externally publishedYes


  • Attention
  • Linear separability
  • Visual search

ASJC Scopus subject areas

  • Language and Linguistics
  • Experimental and Cognitive Psychology
  • Sensory Systems
  • Linguistics and Language


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