CP wk 3

1. Sensation and Perception

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

3. Vision
• Light = electromagnetic radiation
– Wavelength of light determines color

4. Anatomy of the Eye

5. Retina & Photoreceptors
Cones
Rods

7. Primary Visual Cortex
occipital cortex

8. Sensation: Receiving Messages
About the World
• Sense organs
– See, hear, taste, smell, touch, balance, and
experience the world
– Sensory receptor cells transmit sensation
– Perception – interpreting information and
forming images
– Top-down / bottom-up

9. Feature Analysis
• Lines or edges
• Geons
• Phonemes
• Parts of a face (eyes, nose…)
Bottom-Up Processes

10. Feature Analysis
Geons

11. Feature Search
Feature Search: searching for a target that differs from all
distracters by a unique feature.
Conjunction Search: searching for a target that has a particular
combination of the distracters' features.

12. Top-Down Processing
• We perceive by filling
the gaps in what we
sense.
• I _ant ch_co_ate ic_
cr_am.
• Based on our
experiences and
schemas.

13. Bottom-Up and Top-Down Processing
working together
Word Perception
• Connectionist Model

14. An example of context effects in perception.
Word Perception: Top-
Down Processing

15. Perception
• Perceptual processes include:
– Selection refers to choosing
which of many stimuli that will
be processed.
– Organization involves collecting
the information into some
pattern.
– Interpretation involves
understanding the pattern.
• Perception is not passive
• Perceptions can be in error
– Illusions are visual stimuli that
are misinterpreted .

16. Points of Confusion

17. Perceived Motion
• Phi phenomenon
– When two lights flash at
a certain speed, we
perceive a singular light
oscillating back and forth.
– Apparent movement: (see
movement when no
movement has actually
taken place)

18. Sensory Memory: ICONIC
visual persistence

19. A F 2 H
4 T U 7
M R 9 P
High tone
Low tone
Mid tone
Sperling Task: Partial Report

20. Perceptual Segregation

21. Gestalt Organizational Principles
• The German word
gestalt can be translated
to mean form, pattern,
configuration.
• This configuration or
pattern offers an
“organization” to
perception which the
individual experiences.

22. Perception:
Interpreting Sensory Messages
FIGURE-GROUND ORGANIZATION

23. Laws of Perceptual Organization
Law of
Similarity

24. Pointilism
Sunday afternoon at the Grand Jatte
Painters like George Seurat have used laws like
similarity and proximity to paint images.

25. Laws of Perceptual Organization
Law of Continuity Law of Closure

26. Laws of Perceptual Organization
Law of Simplicity

27. Perceptual Constancies
Size Constancy Shape Constancy
Kohler’s TRANSPOSITION: when we attend to an object
we also attend to its RELATIONSHIP with other objects

28. Visual Agnosia

29. Visual Agnosia
• Apperceptive Visual Agnosia
– Cannot recognize by shape
– Cannot copy drawings
– Often involves
‘prosopagnosia’
• Associative Visual Agnosia
– Can copy, but unaware what
it is; cannot assign meaning
to object
– Difficulty in transferring
visual info into words

30. Agnosia

31. Special cognitive mechanisms
dedicated to face perception?
• Early preference for faces (very early)
• Early ability to recognize faces

32. Are faces unique?
The case of face inversion:
– People are generally better at
recognizing upright faces than
other objects.
– However people are worse at recognizing inverted
faces compared to other inverted objects.

33. Thatcher illusion

34. Race and face perception
• Cross-Race Deficit (CRD) and Own-Race
Bias (ORB)
• The Contact Hypothesis
• Face-Space representation

35. Identification of Faces
and Members of
Categories
Prosopagnosia
The Fusiform
Face Area:

36. Anatomy of the Ear
(Sound Waves)

38. Sound Perception
• Matchbook
• McGurk Effect
• McGurk Video
Sound Illusion: Matchbook

39. Sensory Memory: ECHOIC
Do you want to get a cookie?
Do I what?
Oh… a cookie, yeah sure..

40. Glucksberg & Cowen, 1970
“G8KAWHVXPECRT”“….QZ5M42F”
2sec300ms Etc..
Sensory Memory: ECHOIC

41. Glucksberg & Cowen, 1970
Sensory Memory: ECHOIC