1. Cognition
Chapter 3:
Perception

2. The nature of Perception
Experiences resulting from stimulation of the senses
Sometimes an effortful process; sometimes automatic
Occurs in conjunction with action
Involves dynamic processes that accompany and support our actions

3. The nature of Perception
Perceiving a Scene

4. The nature of Perception
Urban Challenge
Click on above picture for video clip

5. The nature of Perception
Blind Man Goes Behind the Wheel of Google's Driverless Car
Click on picture for video clip 
Google Driverless Car

6. The nature of Perception
Computers have problems 
Not anytime soon 

7. Why is it so difficult to Design a perceiving machine?
The stimulus on the receptors is ambiguous
Inverse Projection Problem: Many different objects in the environment can be causing a retinal image; seems to confuse machines
Objects can be hidden or blurred
Machines have trouble perceiving these as a whole
Objects look different from different viewpoints
Machines are lacking in viewpoint invariance

8. Information for human perception
Bottom-up processing
Perceptions influenced by the visual field itself
Can be referred to as “true object” perceptions – making sense from our sensations
Top-down processing
These perceptions are influenced by what the person expects or has experienced before
Our experiences memories, and expectations are what's important here

9. Another view…

10. Top-Down Processing Demo

11. Perceiving Objects
Olivia & Torralba (2007)

12. Perceiving Objects
Can you find 13 faces in this picture?

13. Top-down Processing: Speech
Speech Segmentation
A listeners familiarity with a particular language will alter his or her perception
Identical sound stimuli from two different languages will still lead to different perceptions if one particular listener is familiar with a language that the other listener is not familiar (for example, one listener understands only English, while the other understands only Spanish)

14. Experiencing Pain: Bottom-UP
Direct Pathway Model
Nociceptors (Pain Receptors)
Simple, bare nerve endings that travel along the peripheral nervous system until they reach the spinal cord
Pain messages then are eventually sent to the brain

15. Experiencing Pain: Top-down
Wager, Scott, & Zubieta (2007)
After being injected in the jaw with a stinging saltwater solution, men were given a placebo pill
The men were told that this pill had pain-killing chemicals that would relieve their pain
The men immediately reported that they felt better
Placebo injections led to release of pain-killing opiates
Wiech et al. (2008)
Patients told what to expect requested fewer painkillers after surgery and were sent home 2.7 days earlier than control group

16. Helmholtz’s theory of unconscious inference
Likelihood Principle
Objects are perceived based on what is most likely to have caused the pattern
Note that this means that what we learn about our environment becomes part of the problem solving we do when we encounter an object
Unconscious Inference
Perceptions are result of unconscious assumptions about the environment

17. Helmholtz’s Theory of Unconscious Inference
The display in (a) is usually interpreted as being (b) -- a blue rectangle in front of a red rectangle. It could, however, be (c) -- a blue rectangle and an appropriately positioned six-sided red figure.

18. Gestalt Psychology
Based on the assumption that the whole is different than the sum of its parts
We impose order and structure on what we see
Our expectancies affect how we interpret sensory input

19. Gestalt Principles of Perceptual Grouping
Proximity
If figures are near each other we tend to group them together
Similarity
If figures are similar to each other we tend to group them together
Good Continuation (Continuity)
We tend to perceive smooth, continuous patterns rather than discontinuous ones
Objects that are overlapped by other objects are perceived as continuing behind the overlapping object
When a familiar figure is interrupted we imagine the rest of the figure (we finish the picture)
Simplicity
People tend to group features of a stimulus in a way that provides the simplest interpretation of the world
Law of Pragnanz

20. Gestalt principles of grouping
• Proximity.
Proximity

21. Gestalt principles of grouping
• Similarity.
Similarity

22. Gestalt principles of grouping
• Good Continuation

23. Gestalt principles of grouping
Good Continuation

24. Law of Pragnanz
Of all the possible interpretations, we will select the one that yields the simplest or most stable form.
Simple, symmetrical forms are seen more easily.
In compound letters, the larger figure dominates the smaller ones.
People are more likely to see (b) and (c) not (d) or (e) in figure (a)

25. Law of Pragnanz
This is usually perceived as five circles, not as the nine shapes in (b).

26. Taking Regularities in the environment into account
Regularly occurring physical properties of our environment must be taken into account
Oblique Effect
Regularities in the environment: There is a preponderance of verticals and horizontals
People are more sensitive to these orientations

27. Taking Regularities in the environment into account
Relative Luminance
The amount of light an object reflects is relative to its surroundings

28. Light from above Assumption
Most of our light comes from above so it makes sense that we apply this idea universally
Why does (a) look like indentations in the sand and (b) look like mounds of sand?

29. Semantic Regularities
Hollingworth (2005)
Procedure
Participants observed a scene for 20 seconds
Identical scenes “with target” or “without target” object
Next they are presented the target object alone (center of the screen)
This is followed by a blank screen
They are asked to move a cursor on the blank screen to the place were it was in the original scene (with target group) or to a place they would expect to see the target (non-target group)
Results
With target group was accurate; so was without target group
See next slide 

30. Semantic Regularities
Hollingworth (2005)

31. Jumbled Scenes
The same details are in both stimuli but people identify more objects when the overall scene makes sense

32. Semantic Regularities
Palmer (1975)
Observers saw a context scene flashed briefly, followed by a target picture.
Results showed that:
Targets congruent with the context were identified 80% of the time
Targets that were incongruent were only identified 40% of the time
Stimuli used in Palmer’s (1975) experiment. The scene at the left is presented first, and the observer is then asked to identify one of the objects on the right.

33. Neurons and Knowledge about the environment
Neural activity behind every behavior; connections have been found between neural activity, the nature of the environment, and perception
Neurons are tuned to respond best to things occurring regularly in the environment
The Human Perceiving Machine
Experience-Dependent Plasticity
The brain is changed by its exposure to the environment so it can perceive the environment more efficiently
This was witnessed in experiments on animals and on people
See next slides 

34. Experience-Dependent Plasticity
Procedure
Kittens reared in an environment with just verticals or just horizontals
Vertical-only environment 
Blakemore & Cooper (1970)

35. Experience-Dependent Plasticity
Results
Found that rearing a kitten in certain environments led to changes in how their neurons responded
Specific environment reshaped the kitten’s visual cortex
If reared in an environment with just verticals, the visual cortex would respond mainly to verticals if reared in an environment with just horizontals, the visual cortex would respond mainly to horizontals
Blakemore & Cooper (1970)

36. Greebles & Faces
Gauthier, Tarr, Anderson, Skudlarski, & Gore(1970)

37. “Greeble experiment” Procedure Gauthier et al. (1999)
fMRI used to detect level of activity in an area of the temporal lobe called the fusiform face area (FFA)
Participants asked to respond to either faces or Greeble objects
Extensive “Greeble recognition training” over four days given to participants
Gauthier et al. (1999)
Some of the Greeble family 

38. “Greeble experiment” Results
Greeble novices have higher brain activity for faces than Greebles
Greeble experts responded about the same to Greebles as they did to faces
Interpretation
This provides evidence that the FFA contains not just to faces but to other complex objects as well; the particular objects that the FFA responds to depends on experience with that particular object
Gauthier et al. (1999)

39. Movement facilitates perception
Movement helps us to perceive objects in the environment more accurately
Moving reveals aspects of objects that are not apparent from a single viewpoint
Example: Distorted horse
Interaction of perception and action

40. The physiology of perception and action: What and Where Pathways
Ungerleider & Mishkin (1982)
Monkey presented with two tasks:
Object-discrimination problem
Presented one object; later asked to identify from choice
Lesions of temporal lobe make this difficult
“What” pathway problems
Landmark-discrimination problem
Picking food well closer to a cylinder
Lesions of parietal lobe make this difficult
“Where” pathway problems

41. Perception and action Streams
Neuropsychology
Studying the behaviors of people with brain damage
Dissociations
Situations where one function is present while another function is absent
Single Dissociations
Can be studied in one person; single patient has some things impaired, other things not impaired
Examples: Broca’s Aphasics, Wernicke’s aphasics, Prosopagnosiacs
Double Dissociations
Require two or more people to determine the effects of the brain damage; two or more patients show opposite single impairments
Broca’s & Wernicke’s Aphasics considered together

42. Limitations of Neuropsychology
At least for human processing, brain damage comes about from natural means (accident, etc.)
Members of groups rarely have exactly the same damage (location or extent)
No record of processing or brain organization before the damage
Difficult to assess all possible types of functional impairment
Brain may actually reorganize following damage (called plasticity)

43. Credits
Some of the slides in this presentation prepared with the assistance of the following web sites:
faculty.rio.edu/.../22803%20Cognitive%20Psychology/...
memoryandcognition.wikispaces.com/file/.../Ch2Pt2Localization.ppt