1. 1 Unit 4 Sensation & Perception

2. 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

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

4. 4 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

5. 5 Transduction Sensory pathway – Bundles of neurons that carry information from the sense organs to the brain

6. 6 Sensory Adaptation Sensory adaptation – Loss of responsiveness in receptor cells after stimulation has remained unchanged for a while

7. 7 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)

8. 8 Approximate Perceptual Thresholds of the 5 senses Light – A candle flame at 30 miles on a dark, clear night Sound – The tick of a mechanical watch under quiet conditions at 20 feet Taste - one teaspoon of sugar in 2 gallons of water Smell - on drop of perfume diffused into the entire volume of a three bedroom apartment Touch – The wing of a bee falling on your cheek from a distance of 1 centimeter.

9. 9 Thresholds Weber’s law – The JND is always large when the stimulus intensity is high, and small when the stimulus intensity is low Fechner’s law – S = k log R S = sensation R = stimulus k = constant that differs for each sensory modality

10. 10 Fechner’s law – Also affects stimulus detection States that an increase in the physical magnitude of a stimulus progressively produces smaller increases in perceived magnitude. Now you try to explain that in ENGLISH!!

11. 11 Thresholds Steven’s power law – S = kl a S = sensation k = constant l = stimulus intensity a = a power exponent that depends on the sense being measured

12. 12 Steven’s Power Law More accurate than Fechner’s law Covers a wider variety of stimuli. Like pain and temperature

13. 13 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)

14. 14 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

15. 15 Example of priming S N _ _ _ E L

16. 16 Example continued See if you had been previously primed by a brief presentation of the appropriate word, it would be more likely that you would have found the right answer, even though you weren’t aware of the priming stimulus. Want to know what it was?....

17. 17 Here ya go! S N O R K E L

18. 18 Homework assignment Tonight you need to read “what every skeptic should know about subliminal persuasion.”

19. 19 Today’s Mind Jog!!!!!!!!!!! How Are the Senses Alike? How Are They Different?

20. 20 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 How Are the Senses Alike? How Are They Different?

21. 21 The Anatomy of Visual Sensation Fovea – Area of sharpest vision in the retina 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

22. 22 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

23. 23 Color – Psychological sensation derived from the wavelength of visible light – color, itself, is not a property of the external world The Anatomy of Visual Sensation Visual cortex – Part of the brain – the occipital cortex – where visual sensations are processed

24. 24 Transduction of Light in the Retina

25. 25 Retina located at the very back of the eyeball, is a thin film that contains cells that are extremely sensitive to light light sensitive cells, called photoreceptors, begin the process of transduction by absorbing light waves

26. 26 Cones—concentrated in center of eye (fovea) approx. 6 million allow us to see in bright light, see fine spatial detail, and see different colors adapt quickly one cone often synapses onto only a single ganglion cell (increases visual acuity) CONES! COLOR! CLARITY!

27. 27 Rods—concentrated in periphery approx. 120 million allow us to see in dim light and at night adapt slowly the axons of many rods synapse onto one ganglion cell (increases sensitivity to dim light)

28. 28 Optic nerve nerve impulses flow through the optic nerve as it exits from the back of the eye the exit point is the “blind spot” the optic nerves partially cross and pass through the thalamus the thalamus relays impulses to the back of the occipital lobe in the right and left hemisphere

29. 29 Primary visual cortex *the backs of the occipitals lobes is where primary visual cortex transforms nerve impulses into simple visual sensations Visual association areas the primary visual cortex sends simple visual sensations to neighboring association areas

30. 30 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

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33. 33 Look at the plus at the left for 30 secs then the right

34. 34 Blind Spot Stare at the 3 and move back and forth slowly until the sun disappears

35. 35 If you look at the left (black/white) pattern you will probably notice that the vertical pattern in the center appears to move relative to the horizontal pattern in the surround. This diagram was adapted from a design presented by a Japanese artist whose name is Ouchi. If you see relative motion on the right pattern than you can conclude that the illusion also works with color patterns.

36. 36 Do you see the white diagonal lines coming from this? Really? They aren’t there.

37. 37 Hermann Grid Illusion

38. 38 Scintillating grid illusion

39. 39 More Information? http://www.yorku.ca/eye/toc-sub.htm This website has everything you need to really understand the eye!

40. 40 Neural Pathways in the Human Visual System

41. 41 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

42. 42 Brightness – Sensation caused by the intensity of light waves How the Visual System Creates Color Color blindness – Vision disorder that prevents an individual from discriminating certain colors

43. 43 How the Visual System Creates Brightness Wavelength Color Intensity (amplitude) Brightness

44. 44 Ishihara Test for Color Blindness What numbers do you see revealed in the patterns of dots?

45. 45 Ishihara Test for Color Blindness What numbers do you see revealed in the patterns of dots? 25 29 45 56 6 8

46. 46 Color Blindness The test to the left is simpler. The individual with normal color vision will see a 5 revealed in the dot pattern. An individual with Red/Green (the most common) color blindness will see a 2 revealed in the dots.

47. 47 Connection/reflection! So now that we have covered the eye in detail what differences do you think we will encounter with the next unit on the ear? Any similarities?

48. 48 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

49. 49 Hearing: If a Tree Falls in the Forest... The Physics of Sound High Amplitude Low Amplitude Amplitude – Physical strength of a wave

50. 50 How Sound Waves Become Auditory Sensations Tympanic membrane – The eardrum

51. 51 How Sound Waves Become Auditory Sensations Cochlea – Where sound waves are transduced

52. 52 How Sound Waves Become Auditory Sensations Basilar membrane – Thin strip of tissue sensitive to vibrations Cochlea

53. 53 How Sound Waves Become Auditory Sensations Auditory nerve – Neural pathway connecting the ear and the brain

54. 54 How Sound Waves Become Auditory Sensations Auditory cortex – Portion of the temporal lobe that processes sounds

55. 55 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

56. 56 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

57. 57 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

58. 58 Test your Kinesthetic Awareness Test your current kinesthetic sense with the few simple exercises below. Evaluate how challenging each task is for you. Keep a slight bend in your knees during all activities. 1. Stand on both feet with proper posture (chest up, shoulders back, ears in line with shoulders) for 10 seconds. 2. Stand on one foot maintaining proper posture for 5 seconds. 3. Stand on both feet maintaining proper posture with your eyes closed for 5 seconds. 4. Stand on one foot maintaining proper posture with your eyes closed for 5 seconds

59. 59 Test your Kinesthetic Awareness If you were able to complete all four tasks with ease, you have pretty good kinesthetic awareness. If it was difficult just to maintain proper posture while standing on two feet, you may have some training to do. For most people, the tasks listed above will become increasingly more challenging because the exercises become more novel from one to four. While performing the tasks on one leg and/or with your eyes closed, you may have felt your ankles, knees or even hips wobble back and forth, from side to side or both. Your body was trying to stabilize itself and become aware of its positioning in space.

60. 60 HEARING DEMONSTRATION We need a volunteer to be blindfolded and to sit in the middle of the room!

61. 61 Smell

62. 62 Taste buds – Receptors for taste (primarily on the upper side of the tongue) Taste Gustation – The sense of taste