Visual Search and Attention A Signal Detection Theory_SDT_

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					                         ACT-R : A theory of higher level cognition and its relation to visual attention




                     Introduction
 ACT-R?
   – General system for modeling a wide range of higher level
     cognitive processes.
   – Developed by Anderson(1993)
 We describe theory of visual attention and how it relates
  to the ACT-R theory of higher level cognition.
 Then we describe its extension to a menu-selection task
  and its ability to make some novel predictions about the
  task.
 Assumptions
   – Two types of knowledge
      • Declarative & Procedural




                                                                                               UI Lab.
                          ACT-R : A theory of higher level cognition and its relation to visual attention




  A theory of the visual interface
 Theories of higher level cognition typically ignore
  lower level processes.
   – Two stresses for the plausibility of the resulting models
 Basic overview of the ACT-R system




                                                                                                UI Lab.
                       ACT-R : A theory of higher level cognition and its relation to visual attention




                Visual attention
 ACT-R can select the scale of the features for which it
  searches and the size of the objects it is recognizing.
         Figure 2 : ACT-R
         can see either the H
         or the Xs
         comprising the H,
         Depending on how
         ACT-R sets its
         feature scale.
 The best way to understand how this theory works is
  to see it applied to various tasks involving visual
  attention.



                                                                                             UI Lab.
                          ACT-R : A theory of higher level cognition and its relation to visual attention




 Visual attention-Sperling Task(1/2)
 Whole-report condition
   – Sperling presented subjects with brief presentations (50msec) of
     visual arrays of letters.

                                                  He found that subjects
                                                  could report back 4.4
                                                  letters.

 Partial-report condition
   – Subjects could report 3.3 letters in the selected row.
   – Delaying the auditory cue lower the subjects’ recall
   – See figure 4 in the next slide




                                                                                                UI Lab.
                         ACT-R : A theory of higher level cognition and its relation to visual attention




  Visual attention-Sperling Task(2/2)




 Two dimensions of significance
  – Limitations of visual sensory memory
  – How fast visual attention can move over an array.



                                                                                               UI Lab.
                     ACT-R : A theory of higher level cognition and its relation to visual attention




 Visual attention-Subitizing Task
 Another way to measure switching time for attention
  is to see how long it takes o attend to several objects
  on a screen. (e.g)How many objects are there?)
 There is an increase in latency with number of digits
  to be identified.




                                                                                           UI Lab.
                     ACT-R : A theory of higher level cognition and its relation to visual attention




 Visual attention-Visual search Task
 Another way to investigate the time to shift attention
  is to display an array and ask subjects to search
  among objects for a specific objects




                Results of Visual search task

                                                                                           UI Lab.
                     ACT-R : A theory of higher level cognition and its relation to visual attention




   Visual attention-Conclusions
 We have shown that the ACT-R model is consistent
  with some of the classic results from visual attention




                                                                                           UI Lab.
                          ACT-R : A theory of higher level cognition and its relation to visual attention




 Application to menu-selection data
 Apply ACT-R to the Nilsen data
   – These data are concerned with time to scan a menu as a
     function of the target position of the item in the menu.
   – The menu consists of a set of digits(1 to 9) randomly ordered
     vertically
   – A linear function is obtained with a slope of 103msec per position.




                                                                                                UI Lab.
                    ACT-R : A theory of higher level cognition and its relation to visual attention




                 Conclusions
 We properly model the basic processes of visual
  attention and that they matter in a traditional HCI
  task such as menu scanning.
 ACT-R provides an architecture in which to work out
  these complex interactions with visual attention for
  both simple and complex tasks.




                                                                                          UI Lab.

				
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