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Perception

Why is recognizing objects easy for humans but difficult for computers? This exploration of perception delves into the dynamics of sensory information and how it forms our understanding. We examine concepts like perceptual constancies—shape and size constancy—as well as the Gestalt principles of organization such as proximity, similarity, and closure. Additionally, we address bottom-up and top-down processing, comparing how humans process stimuli versus the template matching approach used by machines. Insights into featural analysis and prototype matching reveal the complexities behind object recognition.

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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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