1. The Visual System

2. Just for fun, let’s test your awareness of your surroundings…
The Awareness Test
Just for fun, let’s test your awareness of your surroundings…

3. How do we see? No light? No sight!
light enters the eye as waves of electromagnetic energy
length of the wave determines a light’s color
the height of the wave (amplitude) determines brightness

4. Structure of the Visual System

5. Optic Nerve (1)
nerve that carries visual information from the eye to the occipital lobes of the brain

6. Blind Spot (2) where the optic nerve exits the eye
no rods and cones at this point, so there is a small blind spot in vision (pg. 166)

7. Retina (3) has cells that convert light energy to nerve impulses
made up of three layers of cells:
Receptor cells
Bipolar cells
Ganglion cells

8. Receptor Cells
sight - change light into neural impulses the brain can understand
visual system has two types of receptor cells – rods and cones

9. Rods
only detect black, white, and shades of gray

10. Cones
detect sharp images and color
cluster at the fovea

11. Bipolar Cells middle layer of retina
gather information from rods & cones and pass it on to the ganglion cells

12. Ganglion Cells axons of ganglion cells form the optic nerve
blind spot is created where optic nerve exits the eye (page 166)

13. Cornea (4) outside layer on the front of the eyeball two tasks:
focuses light by bending it toward a central focal point
protects the eye

14. Pupil (5) opening in center of eye
controls amount of light entering the eye (surrounded by the iris)

15. Iris (6) colored portion of the eye
regulates the size of the pupil by changing its size - allowing more or less light to enter the eye

16. Lens (7) focuses the image on the back of the eye (retina)
muscles that change the thickness of the lens change how the light is bent thereby focusing the image

18. Fovea central focal point of the retina
spot where vision is best (most detailed)

19. Color Vision Theories

20. Trichromatic (three-color) Theory
cones are “tuned” to be sensitive to red, green & blue wavelengths of light
all the colors we see are a combination of these three colors

21. Color Deficient Vision
people who lack one of the three types of cones
usually the red or green receptors are missing
inherited & found more in males

22. Opponent-Process Theory of Color
color-processing neurons oppose one another:
red – green
yellow – blue
black – white
light that stimulated one half of the pair inhibits the other half

25. Hearing

26. Sound
sound comes in waves that are produced by vibration

28. The Structure of the Auditory System

29. Auditory Canal (6)
opening where sound waves enter the ear for processing

30. Tympanic Membrane/Eardrum (7)
transfers sound vibration from the air to the ossicles

31. Tympanic Membrane (w/ tear)

32. Ossicles
three tiny bones that transfer sound waves from the eardrum to the cochlea
hammer (5)
anvil (4)
stirrup (3)

33. Ossicles – Hammer, Anvil, Stirrup

34. Oval Window receives sound vibration from the ossicles
vibrates the fluid in the cochlea

35. Cochlea (2) where sound waves are changed into neural impulses
filled with fluid

36. Cochlea

37. Hair Cells
receptor cells in the cochlea that change sound vibrations into neural impulses

38. Hair Cells

39. Semicircular Canals
used in sensing body orientation and balance (vestibular sense)
relies on fluid in the canals

40. Auditory Nerve (1) formed by fibers at the base of each hair cell
nerve that carries sound from the ears to the temporal lobes

41. How can we tell the difference between different sounds?
3 Theories:
place theory
volley theory
frequency theory

42. Place Theory of Hearing
different types of sound waves vibrate different locations/places on the cochlea
high sounds vibrate one area, low sounds another
problem: very low sounds cause entire cochlea to vibrate

43. Frequency Theory of Hearing
frequency with which the cochlea is vibrated tells us what sound we hear
problem: cannot explain how we tell the difference between high-pitched sounds (neurons can only fire so fast)

44. Volley Theory of Hearing
sensory neurons in the cochlea (the hair cells) fire in groups, as volleys
pattern of firing allows us to tell the difference between sounds

45. Sensation

46. Sensation awareness of the world
process where our sensory systems & nervous system receive stimuli from the environment

47. Perception interpretation of sensory information
process of organizing & interpreting sensory information

48. Two ways we process information:
bottom-up processing
analyze the raw material entering through the eyes, ears, etc.
top-down processing
focus on expectations & experiences in interpreting sensory information

49. Interpret this Sensory Information…
I’m going to Fl --- for spring break.
“Daylight savings time ends tomorrow, and so people should remember to change their …”
“ ”

50. How do you interpret this sensory information?
Perception in Action
How do you interpret this sensory information?

51. Top-down or Bottom-up? Example (don’t write this )
Identify an unknown object based on elements of sensation:
red sphere
cool, hard surface
fits comfortably in your hand
pleasant aroma
satisfying crunch when bitten
tastes both sweet and tart
Analysis of this data leads to the perception that the unknown object is an _________________.

52. Top-down or Bottom-up? Example (don’t write this either)
Would the descriptions below be processed top-down or bottom-up? Explain.
red sphere
cool, hard surface
fits comfortably in your hand
pleasant aroma
satisfying crunch when bitten
tastes both sweet and tart
What types of sensations would you experience when eating the food pictured to the right?

53. Illusions
Module 10: Perception

54. Illusions misinterpreting sensory stimuli
help researchers understand how sensation and perception normally works

55. Müller-Lyer Illusion

56. Müller-Lyer Illusion
Most people think segment AB equals BC. In reality AB is much longer than BC.
Theory: we have learned to interpret arrowheads at the ends of a line as an indication of distance

57. Müller-Lyer Illusion

58. Müller-Lyer Illusion

59. Müller-Lyer Illusion

60. Ames Room Photos explain the photos at the top of page 200
video Segment: “Ames Room Illusion Explained”

61. Ames Room Illusion: Secret Revealed