1. Sensation & Perception
Chapter 4
Sensation & Perception
This multimedia product and its contents are protected under copyright law. The following are prohibited by law:
Any public performance or display, including transmission of any image over a network;
Preparation of any derivative work, including the extraction, in whole or in part, of any images
Any rental, lease or lending of the program.
ISBN:
Copyright © Allyn and Bacon 2007

2. Sensation and Perception
Sensation – An early stage of perception in which neurons in a receptor create an internal pattern of nerve impulses that represent the conditions that stimulated it – either inside or outside the body
Perception – A process that makes sensory patterns meaningful and more elaborate
Copyright © Allyn and Bacon 2006

3. How Does Stimulation Become Sensation?
The brain senses the world indirectly because the sense organs convert stimulation into the language of the nervous system: neural impulses
Copyright © Allyn and Bacon 2006

4. Transduction
Transforming signals into neural impulses. Information goes from the senses to the thalamus , then to the various areas in the brain.

5. Sensory Adaptation
Decreased responsiveness to stimuli due to constant stimulation. We become used to a level of stimulation which doesn’t change.
Do you feel your underwear all day?

6. Cocktail-party phenomenon
The cocktail party effect describes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations. Form of selective attention.

7. Copyright © Allyn and Bacon 2006
Transduction
Transduction – Transformation of one form of energy into another – especially the transformation of stimulus information into nerve impulses
Receptors – Specialized neurons that are activated by stimulation and transduce (convert) it into a nerve impulse
Copyright © Allyn and Bacon 2006

8. Copyright © Allyn and Bacon 2006
Transduction
Sensory pathway – Bundles of neurons that carry information from the sense organs to the brain
Copyright © Allyn and Bacon 2006

9. Copyright © Allyn and Bacon 2006
Thresholds
Absolute threshold – Amount of stimulation necessary for a stimulus to be detected
Difference threshold – Smallest amount by which a stimulus can be changed and the difference be detected (also called just noticeable difference – JND)
Copyright © Allyn and Bacon 2006

10. Copyright © Allyn and Bacon 2006
Thresholds
Weber’s law – The JND is always large when the stimulus intensity is high, and small when the stimulus intensity is low
Copyright © Allyn and Bacon 2006

11. Signal Detection Theory
Signal detection theory – Perceptual judgment as combination of sensation and decision-making processes
Stimulus event
Neural activity
Comparison with personal standard
Action (or no action)
Copyright © Allyn and Bacon 2006

12. Subliminal Persuasion
Studies have found that subliminal words flashed briefly on a screen can “prime” a person’s later responses
No controlled research has ever shown that subliminal messages delivered to a mass audience can influence people’s buying habits
Copyright © Allyn and Bacon 2006

13. How Are the Senses Alike? How Are They Different?
The senses all operate in much the same way, but each extracts different information and sends it to its own specialized processing region in the brain
Copyright © Allyn and Bacon 2006

14. The Anatomy of Visual Sensation
Retina – Light-sensitive layer at the back of the eyeball
Photoreceptors – Light-sensitive cells in the retina that convert light energy to neural impulses
Rods – Sensitive to dim light but not colors
Cones – Sensitive to colors but not dim light
Fovea – Area of sharpest vision in the retina
Copyright © Allyn and Bacon 2006

15. The Anatomy of Visual Sensation
Optic nerve – Bundle of neurons that carries visual information from the retina to the brain
Blind spot – Point where the optic nerve exits the eye and where there are no photoreceptors
Copyright © Allyn and Bacon 2006

16. The Anatomy of Visual Sensation
Visual cortex – Part of the brain – the occipital lobe – where visual sensations are processed
Color – Psychological sensation derived from the wavelength of visible light – color, itself, is not a property of the external world
Copyright © Allyn and Bacon 2006

17. Transduction of Light in the Retina
Copyright © Allyn and Bacon 2006

18. Copyright © Allyn and Bacon 2006
Afterimages
Afterimages – Sensations that linger after the stimulus is removed
In the following slide, fix your eyes on the dot in the center of the flag
Copyright © Allyn and Bacon 2006

19. Copyright © Allyn and Bacon 2006

20. Copyright © Allyn and Bacon 2006

21. Neural Pathways in the Human Visual System
Copyright © Allyn and Bacon 2006

22. How the Visual System Creates Color
Electromagnetic spectrum – Entire range of electromagnetic energy, including radio waves, X-rays, microwaves, and visible light
Visible spectrum – Tiny part of the electromagnetic spectrum to which our eyes are sensitive
Copyright © Allyn and Bacon 2006

23. How the Visual System Creates Color
Color blindness – Vision disorder that prevents an individual from discriminating certain colors
Brightness – Sensation caused by the intensity of light waves
Copyright © Allyn and Bacon 2006

24. Color Vision
Two Major Theories

25. Trichromatic Theory
Three types of cones: Red Blue Green These three types of cones can make millions of combinations of colors. Does not explain afterimages or color blindness well.

26. Opponent-Process theory
The sensory receptors come in pairs. Red/Green Yellow/Blue Black/White If one color is stimulated, the other is inhibited.

27. Copyright © Allyn and Bacon 2006
Color Blindness
Copyright © Allyn and Bacon 2006

28. How the Visual System Creates Brightness
Wavelength
Intensity (amplitude)
Color
Brightness
Copyright © Allyn and Bacon 2006

29. Hearing: If a Tree Falls in the Forest...
The Physics of Sound
Frequency – Number of cycles completed by a wave in a given amount of time
Low Frequency
High Frequency
Copyright © Allyn and Bacon 2006

30. Hearing: If a Tree Falls in the Forest...
The Physics of Sound
Amplitude – Physical strength of a wave
High Amplitude
Low Amplitude
Copyright © Allyn and Bacon 2006

31. Transduction in the ear
Sound waves hit the eardrum then anvil then hammer then stirrup then oval window. Everything is just vibrating. Then the cochlea vibrates. The cochlea is lined with mucus called basilar membrane. In basilar membrane there are hair cells. When hair cells vibrate they turn vibrations into neural impulses which are called organ of Corti. Sent then to thalamus up auditory nerve.
It is all about the vibrations!!!

32. How Sound Waves Become Auditory Sensations
Tympanic membrane – The eardrum
Copyright © Allyn and Bacon 2006

33. How Sound Waves Become Auditory Sensations
Cochlea – Where sound waves are transduced
Copyright © Allyn and Bacon 2006

34. How Sound Waves Become Auditory Sensations
Basilar membrane – Thin strip of tissue sensitive to vibrations
Cochlea
Copyright © Allyn and Bacon 2006

35. How Sound Waves Become Auditory Sensations
Auditory nerve – Neural pathway connecting the ear and the brain
Copyright © Allyn and Bacon 2006

36. How Sound Waves Become Auditory Sensations
Auditory cortex – Portion of the temporal lobe that processes sounds
Copyright © Allyn and Bacon 2006

37. The Psychology of Pitch, Loudness, and Timbre
Pitch – Sensory characteristic of sound produced by the frequency of the sound wave
Loudness – Sensory characteristic of sound produced by the amplitude (intensity) of the sound wave
Timbre – Quality of a sound wave that derives from the wave’s complexity
Copyright © Allyn and Bacon 2006

38. Nerve (sensorineural) Deafness
Conduction Deafness
Nerve (sensorineural) Deafness
Something goes wrong with the sound and the vibration on the way to the cochlea. You can replace the bones or get a hearing aid to help.
The hair cells in the cochlea get damaged. Loud noises can cause this type of deafness. NO WAY to replace the hairs. Cochlea implant is possible.

39. Copyright © Allyn and Bacon 2006
Deafness
Conduction deafness – An inability to hear resulting from damage to structures of the middle or inner ear
Nerve deafness – An inability to hear, linked to a deficit in the body’s ability to transmit impulses from the cochlea to the brain, usually involving the auditory nerve or higher auditory processing centers
Copyright © Allyn and Bacon 2006

40. Copyright © Allyn and Bacon 2006
Smell
Olfaction – Sense of smell
Olfactory bulbs – Brain sites of olfactory processing
Pheromones – Chemical signals released by organisms to communicate with other members of the species
Copyright © Allyn and Bacon 2006

41. Copyright © Allyn and Bacon 2006
Smell
Copyright © Allyn and Bacon 2006

42. Copyright © Allyn and Bacon 2006
Taste
Gustation – The sense of taste
Taste buds – Receptors for taste (primarily on the upper side of the tongue)
Copyright © Allyn and Bacon 2006

43. Copyright © Allyn and Bacon 2006
The Skin Senses
Touch
Warmth
Cold
Copyright © Allyn and Bacon 2006

44. Copyright © Allyn and Bacon 2006
Pain
Placebos – Substances that appear to be drugs but are not
Placebo effect – A response to a placebo caused by subjects’ belief that they are taking real drugs
Copyright © Allyn and Bacon 2006

45. Copyright © Allyn and Bacon 2006
Position and Movement
Vestibular sense – Sense of body orientation with respect to gravity
Kinesthetic sense – Sense of body position and movement of body parts relative to each other
Copyright © Allyn and Bacon 2006

46. What is the Relationship Between Perception and Sensation?
Perception brings meaning to sensation, so perception produces an interpretation of the external world, not a perfect representation of it
Copyright © Allyn and Bacon 2006

47. What is the Relationship Between Perception and Sensation?
Percept – Meaningful product of a perception
Copyright © Allyn and Bacon 2006

48. The Machinery of Perceptual Processing
Feature detectors – Cells in the cortex that specialize in extracting certain features of a stimulus
Binding problem – A major unsolved mystery in cognitive psychology, concerning the physical processes used by the brain to combine many aspects of sensation to a single percept
Copyright © Allyn and Bacon 2006

49. Bottom-Up and Top-Down Processing
Bottom-up processing – Analysis that emphasizes characteristics of the stimulus, rather than internal concepts
Top-down processing – Emphasizes perceiver's expectations, memories, and other cognitive factors
Copyright © Allyn and Bacon 2006

50. Perceptual Constancies
Perceptual constancy – Ability to recognize the same object under different conditions, such as changes in illumination, distance, or location
Copyright © Allyn and Bacon 2006

51. Perceptual Ambiguity and Distortion
Illusions – Demonstrably incorrect experience of a stimulus pattern, shared by others in the same perceptual environment
Ambiguous figures – Images that are capable of more than one interpretation
Copyright © Allyn and Bacon 2006

52. Copyright © Allyn and Bacon 2006
Perceptual Illusions
Do you see or ?
Copyright © Allyn and Bacon 2006

53. Copyright © Allyn and Bacon 2006
Perceptual Illusions
The Herman Grid
Do you see small gray squares between the black squares?
Copyright © Allyn and Bacon 2006

59. Theoretical Explanations for Perception
Learning-based inference – View that perception is primarily shaped by learning, rather than innate factors
Perceptual set – Readiness to detect a particular stimulus in a given context
Copyright © Allyn and Bacon 2006

60. Cultural Influences on PerceptionB
Which box is bigger, A or B?
Copyright © Allyn and Bacon 2006

61. Copyright © Allyn and Bacon 2006
The Gestalt Approach
Gestalt psychology – View that much of perception is shaped by innate factors built into the brain
Figure – Part of a pattern that commands attention
Ground – Part of a pattern that does not command attention; the background
Copyright © Allyn and Bacon 2006

62. Copyright © Allyn and Bacon 2006
The Gestalt Approach
Subjective contours – Boundaries that are perceived but do not appear in the stimulus pattern
Closure – Tendency to fill in gaps in figures and see incomplete figures as complete
Copyright © Allyn and Bacon 2006

63. The Gestalt Laws of Perceptual Grouping
Similarity
Proximity
Continuity
Common fate
Prägnanz
Copyright © Allyn and Bacon 2006

64. Copyright © Allyn and Bacon 2006
Law of Prägnanz A
BIRD
IN THE
THE HAND
Copyright © Allyn and Bacon 2006

68. Copyright © Allyn and Bacon 2007
End of Chapter 4
Copyright © Allyn and Bacon 2007