1. Cognition Chapter 3: Perception

2.  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 THE NATURE OF PERCEPTION

3. Perceiving a Scene

4.  Urban Challenge THE NATURE OF PERCEPTION

5.  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. Form Perception & Feature Analysis Bottom-Up Processing Relies on properties of the stimulus such as patterns of light and dark areas. Top-Down Processing Relies on higher-level information such as prior knowledge and experience. What is in this picture? Modeled after a PPT slide created by Kevin Richardson in 1998 and made available through the American Psychological Society

10. Another view…

11. Top-Down Processing Demo

12. Perceiving Objects Olivia & Torralba (2007)

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

14. 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) Top-down Processing: Speech

15. 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

16. 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

17. 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 HELMHOLTZ’S THEORY OF UNCONSCIOUS INFERENCE

18. 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. Helmholtz’s Theory of Unconscious Inference

19. 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

20. 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

21. GESTALT PRINCIPLES OF GROUPING Proximity. Proximity

22. GESTALT PRINCIPLES OF GROUPING Similarity. Similarity

23. GESTALT PRINCIPLES OF GROUPING Good Continuation

24. GESTALT PRINCIPLES OF GROUPING Good Continuation

25.  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. LAW OF PRAGNANZ People are more likely to see (b) and (c) not (d) or (e) in figure (a)

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

27. 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 TAKING REGULARITIES IN THE ENVIRONMENT INTO ACCOUNT

28. Relative Luminance  The amount of light an object reflects is relative to its surroundings

29.  Most of our light comes from above so it makes sense that we apply this idea universally LIGHT FROM ABOVE ASSUMPTION Why does (a) look like indentations in the sand and (b) look like mounds of sand?

30. 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 SEMANTIC REGULARITIES See next slide 

31. Hollingworth (2005) SEMANTIC REGULARITIES

32. JUMBLED SCENES The same details are in both stimuli but people identify more objects when the overall scene makes sense

33. 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.

34.  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 NEURONS AND KNOWLEDGE ABOUT THE ENVIRONMENT See next slides 

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

36. 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 Experience-Dependent Plasticity Blakemore & Cooper (1970)

37. GREEBLES & FACES Gauthier, Tarr, Anderson, Skudlarski, & Gore(1970)

38. Procedure  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 “GREEBLE EXPERIMENT” Gauthier et al. (1999) Some of the Greeble family 

39. 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 “GREEBLE EXPERIMENT” Gauthier et al. (1999)

40.  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 MOVEMENT FACILITATES PERCEPTION

41. 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 THE PHYSIOLOGY OF PERCEPTION AND ACTION: WHAT AND WHERE PATHWAYS

42.  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 PERCEPTION AND ACTION STREAMS

43. 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)

44. CREDITS  Some of the slides in this presentation prepared with the assistance of the following web sites:  faculty.rio.edu/.../22803%20Cognitive%20Psychology/...  www.smccd.edu/accounts/irigoyen/.../chapter3.ppt www.smccd.edu/accounts/irigoyen/.../chapter3.ppt  www.csupomona.edu/~nalvarado/PSY334%20PPTs/Chap2.ppt www.csupomona.edu/~nalvarado/PSY334%20PPTs/Chap2.ppt  www.ba.metu.edu.tr/~cagli/.../ppt/solomon_cb09_ppt_02.ppt www.ba.metu.edu.tr/~cagli/.../ppt/solomon_cb09_ppt_02.ppt  memoryandcognition.wikispaces.com/file/.../Ch2Pt2Localization.ppt  http://books.google.com/books?id=4LI8AwAAQBAJ&pg=PT86&lpg=PT 86&dq=cognition+goldstein+pnc+park&source=bl&ots=Z2XtvlpaCo&si g=LjcXxywPxkn0P42nu2KX6nXryiI&hl=en&sa=X&ei=6aMEVLa9Otafgg SnnoGYDA&ved=0CB4Q6AEwAA#v=onepage&q=cognition%20goldstein %20pnc%20park&f=false