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Perception

Perception. Question of the Day. Why is recognizing an object so easy for humans, but so difficult for computers?. Points of Confusion. http://i.ivillage.com/E/325/Celebrities/FaceReader/FaceReaderIntro_325.jpg. http://www.apogeephoto.com/mag1-6/mag2-5mf1.jpg. Perception:

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Perception

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  1. Perception

  2. Question of the Day • Why is recognizing an object so easy for humans, but so difficult for computers?

  3. Points of Confusion http://i.ivillage.com/E/325/Celebrities/FaceReader/FaceReaderIntro_325.jpg http://www.apogeephoto.com/mag1-6/mag2-5mf1.jpg

  4. Perception: attaching meaning to incoming sensory information What is this?

  5. Figure 2-1Distal Stimuli, Proximal Stimuli, and Percepts.

  6. Perceptual Constancies • Shape Constancy • Tendency to see an object as keeping its form despite changes in orientation.

  7. Perceptual Constancies • Size Constancy • Tendency to view an object as constant in size despite changes in the size of the retinal image. http://www.psychologie.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/assets/images/constancy.jpg

  8. Perceptual Constancies • Illusions

  9. Gestalt ApproachFigureGround Figure 2-2

  10. Gestalt ApproachSubjectiveContoursFigure 2-3

  11. Gestalt principles of Perceptual Organization • Proximity http://www.sapdesignguild.org/resources/optical_illusions/images/proximity.gif

  12. Gestalt principles of Perceptual Organization • Similarity • http://www.aber.ac.uk

  13. http://chd.gse.gmu.edu/immersion/knowledgebase/strategies/cognitivism/gestalt/Image6.gifhttp://chd.gse.gmu.edu/immersion/knowledgebase/strategies/cognitivism/gestalt/Image6.gif not this what most people would see Gestalt principles of Perceptual Organization • Good continuation • http://www.aber.ac.uk

  14. Gestalt principles of Perceptual Organization • Closure http://daphne.palomar.edu http://www.aber.ac.uk/media/Modules/MC10220/Images/seal.gif http://graphicdesign.spokanefalls.edu/tutorials/process/gestaltprinciples/closure/closure_a.gif

  15. Gestalt principles of Perceptual Organization • Common fate

  16. Figure 2-5 Gestalt principles of Perceptual Organization

  17. Two Interacting Aspects of Perception • Bottom-up processing • Processing based on incoming stimuli from the environment • Also called data-based processing • Top-down processing • Processing based on the perceiver’s previous knowledge • Also called knowledge-based processing http://jurmo.us/log/wp-content/uploads/2007/04/topdownbottomup.jpg

  18. Bottom-Up Processes The number “4” from the check is compared to a list of stored templates. Template matching

  19. Bottom-Up Processes Problems with Template Matching • Large number of stored templates needed • How are new templates made? • An object can be “more or less” like the template • We can recognize many variations of a template

  20. Bottom-Up Processes Figure 2-8

  21. Bottom-Up Processes Featural Analysis features (“parts”) of a stimulus are recognized by feature detectors and added together to help us perceive an object • Lines or edges • Geons • Phonemes • Parts of a face (eyes, nose…)

  22. Featural Analysis Geons

  23. Figure 2-14 A depiction of Selfridge’s (1959) Pandemonium model. Featural Analysis Letter detection

  24. Bottom-Up Processes Featural Analysis Feature Properties • Detectors can respond at different intensities • Connections between detectors can have different strengths • It is possible to change what a detector will respond to

  25. Bottom-Up Processes Prototype Matching

  26. Bottom-Up Processes Prototype Matching http://www.palm.com

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