title: Field of attention for instantaneous object recognition.
abstract: BACKGROUND
  Instantaneous object discrimination and categorization are fundamental cognitive capacities performed with the guidance of visual attention. Visual attention enables selection of a salient object within a limited area of the visual field; we referred to as "field of attention" (FA). Though there is some evidence concerning the spatial extent of object recognition, the following questions still remain unknown: (a) how large is the FA for rapid object categorization, (b) how accuracy of attention is distributed over the FA, and (c) how fast complex objects can be categorized when presented against backgrounds formed by natural scenes.
  
  
  RESULTS
  To answer these questions, we used a visual perceptual task in which subjects were asked to focus their attention on a point while being required to categorize briefly flashed (20 ms) photographs of natural scenes by indicating whether or not these contained an animal. By measuring the accuracy of categorization at different eccentricities from the fixation point, we were able to determine the spatial extent and the distribution of accuracy over the FA, as well as the speed of categorizing objects using stimulus onset asynchrony (SOA). Our results revealed that subjects are able to rapidly categorize complex natural images within about 0.1 s without eye movement, and showed that the FA for instantaneous image categorization covers a visual field extending 20° × 24°, and accuracy was highest (>90%) at the center of FA and declined with increasing eccentricity.
  
  
  CONCLUSIONS
  In conclusion, human beings are able to categorize complex natural images at a glance over a large extent of the visual field without eye movement.
authors.affiliation: Key Laboratory for Neuroinformatics, Ministry of Education of China, University of Electronic Sciences and Technology, Chengdu, China.
authors.forename: Jian-Gao
authors.initials: JG
authors.lastname: Yao
authors.forename: Xin
authors.initials: X
authors.lastname: Gao
authors.forename: Hong-Mei
authors.initials: HM
authors.lastname: Yan
authors.forename: Chao-Yi
authors.initials: CY
authors.lastname: Li
mesh_terms: D000328:Adult; D001288:Attention; D005133:Eye Movements; D005364:Field Dependence-Independence; D006801:Humans; D010364:Pattern Recognition, Visual; D014796:Visual Perception; D055815:Young Adult