Sensation notices Various stimuli Of what is out there In reality

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2 Sensation and Perception Are skills we need For hearing, feeling And helping us to see I will begin with A few definitions This way confusion Has some prevention Sensation notices Various stimuli Of what is out there In reality 2

3 Perception in contrast Happens in the brain It in no way is Something mundane Exactly how it works Is a mystery Because it s different For you and for me An external stimulus Has energy But Some have molecules Like a cup of tea This Outside energy is translated Into (neural) signals That are somewhat graded Gustav Fechner created psychophysics These were like Sense system yardsticks This process is called TRANSDUCTION 2

4 Absolute thresholds Are the minimums Of what gets in To sensory Systems 3

5 Like a candle flame On a starless night From 30 miles away is within our sight 4

6 Or the tick of a clock From 30 feet 5

7 Or the weight of a fly s wing Falling on your cheek 6

8 A single drop of perfume Diffused in six rooms 7

9 Or two gallons of water Sugared with a teaspoon 8

10 These are thresholds Of our sense systems Is it there or is it not That is the question 9

11 Thresholds are also About differences Kinda like the taste Of different kisses The minimal difference Is the JND It s not the same For you and me But Weber s Law Gave us some guidance For weight and sound and Taste and brightness 10

12 Just Noticeable Difference 10

13 Sometimes our world Seems very cluttered (Signal) Detection theory Is the new buzzword Everyone makes Different decisions What we see Comes from motivations 11

14 A saving grace is Sensory adaptation Over time Senses have less action 12

15 Like getting used To a blinding light 13

16 Or adjusting to The dark at night 14

17 When it comes to vision A good place to start Is the creation Of the Snellen chart This chart is famous As you can see It helps your doctor Find acuity 15

18 But first we must Take a look at light Its unique properties Determine our sight Light waves have Three properties These determine Exactly what we see 16

19 The length of a light wave Determines its hue 17

20 The brightness of colors Is due to amplitude 18

21 The richness of color Is known as purity It is due to Light s complexity 19

22 But Not all light is seen by the eye The wavelength spectrum shows us why Some of these waves Are too short to see Unless you happen To see like a bee Other waves are way too long But not too long To carry a song Refers to radio waves 20

23 The human eye Is an amazing thing Its various parts Work like a team 21

24 To focus light On the retina Color and detail In the fovea To Focus too close Is myopia Focus too far and hyperopia 22

25 Either way These Problems are correctable Corrective lenses Make things visible 23

26 But the real miracle is Light transduction This is how the Retina functions Rods and cones are Photoreceptors 24

27 Rods see black and white 25

28 But Cones see colors 26

29 Rods are for low light And see shades of gray Cones in the fovea: Details of the day Rods and cones also Differ in number More rods than cones But it s not a blunder 27

30 Image processing Begins in the retina This is done By retinal ganglia 28

31 These cells have Different receptive fields Center on or center off Determine neural yields 29

32 Color vision requires Cones in three types They respond to Different colored lights 30

33 Mixing these colors Gives variety To all the colors That we can see 31

34 But cones get tired A sort of fatigue This makes (after)images You can barely see 32

35 But The real stuff of vision Is in the human brain Different parts collaborate Let me explain 33

36 Some cells are programmed To see certain things Like lines at an angle 34

37 Or birds on the wing 35

38 The brain is the computer To help us to see Things complex Or simple like a G 36

39 The gestalt psychologists Did a lot of research To help understand How perception works They developed Perceptual organization These principles are Part of our doctrine 37

40 Sometimes figures are ambiguous Figure or ground May confuse us 38

41 Perceiving depth Requires many cues Some are for one eye And others are for two 39

42 Relative size uses Familiarity 40

43 3D images need (Binocular) disparity 41

44 We can tell what is near or what is far Sometimes while Riding in a moving car 42

45 Like the Linear perspective of rail road tracks 43

46 or the texture gradient of dry river cracks 44

47 Sometimes objects Block One another 45

48 Or the relative heights Of a bunch of flowers 46

49 This Understanding of How perception works Can help to make Some interesting quirks The Ames Room plays With relative heights 47

50 Or we can see motion In blinking lights 48

51 Our visual system is simply Amazing Its complexity leaves me Quaking 49

52 But also remarkable: The Ability to hear! Audition is more Than what meets the ear 50

53 To understand hearing You have to know sound Here are some basics To give us common ground Sound waves have three Properties Pitch depends on Frequencies 51

54 Loudness is due to Amplitude Like a musician With an attitude 52

55 And sounds may be pure Or very complex Like what we hear In a multiplex 53

56 The ear itself is Very Marvelous From outer to inner It s incredulous 54

57 From the ear drum to the cochlea too much sound and you ve got trauma Sound waves are read By the basilar membrane 55

58 Which sends signals Up into the brain Actually, hair cells are stimulated by vibrations in the basilar membrane. These are actually dendritic terminals, which send the messages to their cell bodies which relay them to other cells in the brain. 56

59 Having two ears Detects the source of sound Loudness and timing Help us look around 57

60 The bodily senses are More than skin deep The skin itself is Something to keep Under the skin are many Receptors They detect pain And sometimes pleasures 58

61 Maintaining balance Is part of the picture In the ear is a System vestibular 59

62 Chemical senses add Flavor to our lives 60

63 Like Smelling pheromones And tasting good wines 61

64 Wouldn t it be nice If we were synesthetes That way we taste The things that we see 62

65 Speaking of seeing I see that I am done In rhyming this chapter I think that I have won! I m done, I m out! I m Professor Hal! 63