1. Perception

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

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

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

5. Gestalt Approach Figure Ground Figure 2-2

6. Gestalt Approach Subjective Contours Figure 2-3

7. Gestalt principles of Perceptual Organization http://www.aber.ac.uk Proximity

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

9. Gestalt principles of Perceptual Organization Good continuation what most people would see not this http://www.aber.ac.uk

10. Gestalt principles of Perceptual Organization Closure http://daphne.palomar.edu

11. Gestalt principles of Perceptual Organization Common fate

12. Figure 2-5 Gestalt principles of Perceptual Organization

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

14. 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 Bottom-Up Processes

15. Figure 2-8 Bottom-Up Processes

16. 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…) Bottom-Up Processes

17. Featural Analysis Geons

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

19. 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

20. Bottom-Up Processes Prototype Matching

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

22. Figure 2-19 An example of context effects in perception. Top-Down Processes

23. Perceptual Learning Change Blindness Word Superiority Effect 12a2b Top-Down Processes OR

24. Bottom-Up and Top-Down Processing working together Word Perception Connectionist Model Features (lines) Letters Words Input I B Bat at

25. Figure 2-24 (p. 73) Example of stimuli used in the PET scan study of processing words. See text for explanation. Word Perception Neuropsychological Perspective

26. Figure 2-30 Examples of how contour information influences recognition in persons with apperceptive agnosia. (A) Patients with apperceptive agnosia have difficulty recognizing this object as a chair because they cannot interpolate the missing contours. (B) Patients with apperceptive agnosia would have difficulty recognizing the chair when it is viewed from this unusual angle. Agnosia

27. Question of the Day Why is recognizing an object so easy for humans, but so difficult for computers?  Stimulus ambiguous  Objects overlap  Parts of objects may be hidden  Differences in lightness/darkness could be from more than one cause

28. Outline Introduction Gestalt perceptual principles Bottom-up processing  Template matching  Featural analysis  Prototype matching Top-down processing Agnosia