Perception
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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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Perception

Perception


Question of the day

Question of the Day

  • Why is recognizing an object so easy for humans, but so difficult for computers?


Points of confusion

Points of Confusion

http://i.ivillage.com/E/325/Celebrities/FaceReader/FaceReaderIntro_325.jpg

http://www.apogeephoto.com/mag1-6/mag2-5mf1.jpg


Perception

Perception:

attaching meaning to incoming sensory information

What is

this?


Figure 2 1 distal stimuli proximal stimuli and percepts

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


Perception

Perceptual Constancies

  • Shape Constancy

    • Tendency to see an object as keeping its form despite changes in orientation.


Perception

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


Perceptual constancies

Perceptual Constancies

  • Illusions


Gestalt approach figure ground figure 2 2

Gestalt ApproachFigureGround Figure 2-2


Gestalt approach subjective contours figure 2 3

Gestalt ApproachSubjectiveContoursFigure 2-3


Gestalt principles of perceptual organization

Gestalt principles of Perceptual Organization

  • Proximity

http://www.sapdesignguild.org/resources/optical_illusions/images/proximity.gif


Gestalt principles of perceptual organization1

Gestalt principles of Perceptual Organization

  • Similarity

  • http://www.aber.ac.uk


Gestalt principles of perceptual organization2

http://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


Gestalt principles of perceptual organization3

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


Gestalt principles of perceptual organization4

Gestalt principles of Perceptual Organization

  • Common fate


Figure 2 5

Figure 2-5

Gestalt principles of Perceptual Organization


Two interacting aspects of perception

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


The number 4 from the check is compared to a list of stored templates

Bottom-Up Processes

The number “4” from the check is compared to a list of stored templates.

Template

matching


Perception

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


Figure 2 8

Bottom-Up Processes

Figure 2-8


Perception

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…)


Perception

Featural Analysis

Geons


Figure 2 14 a depiction of selfridge s 1959 pandemonium model

Figure 2-14 A depiction of Selfridge’s (1959) Pandemonium model.

Featural

Analysis

Letter

detection


Bottom up processes

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


Bottom up processes1

Bottom-Up Processes

Prototype Matching


Perception

Bottom-Up Processes

Prototype Matching

http://www.palm.com


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