Myers’ PSYCHOLOGY (6th Ed)

1. Myers’ PSYCHOLOGY (6th Ed) Chapter 5 Sensation James A. McCubbin, PhD Clemson University Worth Publishers

2. CH. 5: Sensation • Sensation: process by which sensory receptors + nervous system receive & represent stimulusenergy - stimulation of neurons in sensory nerves, such as optical & auditory nerves…creating action potential • Perception: the way weorganize & interpret sensory info, enabling us to recognize meaningful objects & events -helps us to “know” what something is…as long as we have experience with it -prosopagnosia: visual condition -can receive stimulus, but cannot organize it into recognizable things…so can’t recognize it

3. Sensory & perceptual processes work together to help us sort out complex processes “The Forest Has Eyes…”

4. Sensation • Bottom-Up Processing: sensory analysis that begins w/ sense receptors then  brain’s integration of sensory info -neural signals  into action potentials • Top-Down Processing: info processing guided by higher-level mental processes • as when we construct perceptions drawing on our experience & expectations…often what we are used to seeing…& ---what we expect to see EX: prosopagnosia: receiving signals (sensory) & ID facial features, but can’t put it together& name them…but can feel emotional reaction…see son, warm emotions, but no recognition…

5. Sensation- Basic Principles • Thresholds:“How low can you go?” • Psychophysics • study of the relationship between physical characteristics relate to our psychological experience …how intense? How is it changing? • Light- brightness • Sound- volume • Pressure- weight • Taste- sweetness

6. Sensation- Thresholds • Absolute Threshold: minimum stimulation needed to detect a particular stimulus 50% of the time EX: the earphones used in a hearing test… -vision: if we are on top of a mtn., we can see a candle flame on another mtn. 30 miles away (if it is a dark, clear night) -touch: wing of a bee on our cheek -smell: 1 drop of perfume in a 3-rm. Apt. • Difference Threshold (197): minimum difference between two stimuli required for detection 50% of the time • just noticeable difference (JND)

7. Sensation- Thresholds • Signal Detection Theory: predicts how & when we detect the presence of a faint stimulus (signal) amid background stimulation (noise…meaning distracting stuff around you…can be visual) • assumes that there is no single absolute threshold • detection depends partly on person’s • Experience • expectations • motivation • level of fatigue -soldier’s awareness on guard duty? -mom’s can hear baby b/c tuned in to it --how about you & your cell phone?? 

8. 100 Percentage of correct detections 75 50 Subliminal stimuli 25 0 Low Absolute threshold Medium Intensity of stimulus Sensation- Thresholds Subliminal: real or unreal? • When stimuli are just below one’s absolute threshold for conscious awareness, but can be perceived unconsciously • “EAT POPCORN?” • Eliminate bad habits, attain goals? • Can have fleeting effect…but not enduring • Expectations?(197) • Now ads put info into our minds—colors, “cool” in smoking…

9. Sensation- Thresholds • Weber’s Law- to perceive as different, 2 stimuli must differ by a constant minimum %…how much causes a JND? • light intensity- for avg. person to tell a difference in 2 lights, difference must be at least 8% • weight- 2% (5 lbs?) --tone frequency- 0.3% • NOTE: these are rough approximations -affected also by expectations & experience: 50 cent bar  5 cents? How much w/ $40,000 Mercedes? • Sensory adaptation- diminished sensitivity as a consequence of constant stimulation -after constant exposure to a stimulus, nerves fires less frequently…odors, your watch, sounds…but not vision b/c eyes continually move just slightly…but if we held it constant? 

10. Vision- Stabilized Images on the Retina: If truly constant, vision does fade…

11. Benefit of sensory adaptation: Though it reduces our sensitivity, it allows us to focus on new info coming into our environment --we notice novelty…the new, the different… Why is this important? “We perceive the world not as it is, but as it is useful for us to perceive it.” --Effect of TV…why does it hold our attention so well?

12. Vision: • Transduction: conversion of 1 form of energy to another • in sensation, transforming stimulus energies into neural impulses (action potential) • In vision, light is transduced into neural messages (action potentials) from optic nerve to the brain • Wavelength: the distance from the peak of one waveto the peak of the next --determines hue or color (lo- or hi- pitch in sound) • Intensity: amount of energy in a wave determined by amplitude…the height of the wavelength • Brightness or dullness in colors • loudness Humans can only see part of the electromagnetic spectrum…Which can we not see? But bees see ultraviolet (b-199)…snakes see infrared

13. The spectrum of electromagnetic energy

14. Great amplitude… (bright colors, loud sounds) Short wavelength=high frequency (bluish colors, high-pitched sounds) Long wavelength=low frequency (reddish colors, low-pitched sounds) Small amplitude (dull colors, soft sounds) Vision- Physical Properties of Waves

15. Vision: How we transform physical energy into color, etc.: • Cornea- clear outer covering of the eye where light 1st enters • Pupil- adjustable opening in the center of the eye…light comes in from the cornea to the pupil… • Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening by contracting & expanding • Lens- transparent structure behind pupil that changes shape to focus images on the retina --image comes in upside-down

16. Vision

17. Vision • Accommodation- the way the eye’s lens changes shape to help focus near or far objects on the retina • Retina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information ------------------------------------------------------------- Problems in vision: • Acuity- the sharpness of vision: how well we see • Nearsightedness- condition in which nearby objects are seen more clearly than distant objects because distant objects in front of retina (can see close, not far away) [myopia] • Farsightedness- faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina (hyperopia… aka hypermetropia)

18. Vision: When it doesn’t work… Farsighted Nearsighted Normal Vision Vision Vision (elongated) (squatty) (round)

19. Retina’s Reaction to Light- -Receptors: • Rods • peripheral retina • detect black, white and gray • twilight or low light…use for night vision • Cones • near center of retina • fine detail and color vision • daylight or well-lit conditions • Fovea: concentration of cones on retina • Blind spot: no rods or cones…  

20. Retina’s Reaction to Light • Optic nerve- nerve that carries neural impulses from the eye to the brain • Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there • Fovea- central point in the retina, around which the eye’s cones cluster

21. 1. Light hits retina (rods/cones) 2. fires bipolar cells…3. ganglion cells activate optic nerve

22. Receptors in the Human Eye Cones Rods Number 6 million 120 million Location in retina Center Periphery Sensitivity in dim light Low High Color sensitive? Yes No Vision- Receptors

23. Pathways from Eyes to Visual Cortex:optic chiasm = cross-over point to opposite hemispheres

24. Cell’s responses Stimulus Visual Info Processing: The work of D. Hubel & T. Wiesel: • Feature Detectors • nerve cells in the visual cortex of the brain that respond to specific features (p. 204-205) • 3 features: Shape… angle…movement… • Then info goes to special areas of temporal or parietal…faces? Houses? Chairs? • Begins w/ simple shapes & combine into more complex • fMRI used to ID where we look…at what we look

25. How the Brain PerceivesChanging cube? (b-205) Stare at the cube… It will “change” every few seconds!

26. Illusory (illusions) Contours:We fill in areas…Do you see a triangle?Psy not totally sure how all this works…are new research & theories on-going…

27. Visual Info Processing(p. 206) • Parallel Processing: How our brain processes • simultaneous processing of several aspects of a problem simultaneously • EX: Divides a visual scene into color, depth, mov’t, form (shapes) & works on each at same time • Coordinates & combines info into perception • computers = “serial” processing… step 1,2,3,…

29. Visual Information Processing • 2 Theories RE: how we see color: • 1) Trichromatic (three color) Theory: receptors for 3 & they “blend”(Young and Helmholtz) Think paint-mixing! • 3 different retinal color receptors • red • green • Blue

30. Color-Deficient Vision • People who suffer “red-green color blindness” have trouble perceiving the number within the design • BUT…true “color blind – NO cones to process color • What we call C-B is actually color deficiency

31. Visual Information Processing 2) Opponent-Process Theory- opposing retinal processes enable color vision --certain # of each in “balance”…& if one goes on, its opposite goes OFF…then they fire to come back into balance “ON” “OFF” redgreen greenred blueyellow yellowblue black white white black This causes an “afterimage”…remember the flag??

32. Opponent Process- Afterimage Effect

34. Focus on the 3 dots at the center of the picture

36. Visual Information Processing • Color Constancy • Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object • Also in vision, have brightness constancy, shape constancy, & size constancy • These aspects depend on their surroundings

37. I-D which is which type of constancy

38. Audition:the sense of hearing • Amplitude: the loudness or intensity of sound, determined bythe height of a sound wave (hi = bright color) • Frequency: the number of complete wavelengths that pass a point in a given time (hi-freq. colors = blue) • Pitch: a tone’s highness or lowness • depends on frequency • Timbre: the quality of sound…how 1 voice differs from another , or a guitar differs from “C” on a piano • Decibels: measuring unit for sound energy; measures the amplitude

39. The Intensity of Some Common Sounds: Decibels: the measure of amplitude (loudness) in sound

40. Writing: p. 213…Read & respond to the following prompts: • 1) 1st paragraph: Explain how sound waves are processed into sound • 2) 2nd paragraph: Describe the cilia that are on the oval window & the basilar membrane on which the cilia are located. -What is the dangers to these cilia? -What happens if they are damaged? -How can we protect them?

42. Audition- The Ear • Middle Ear • chamber between eardrum & cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window w/ basilar membrane inside. • Inner Ear • innermost part of the ear, continuing the cochlea, semicircular canals, and vestibular sacs • Cochlea • coiled, bony, fluid-filled tube in the inner ear through which contains the basilar membrane • Basilar membrane: tissue in the cochlea; hair cells on the basilar membrane hold cilia…which are moved by vibrations…& this causes firing into the auditory nerve endings  goes to auditory nerve to brain…

43. How we perceive pitch: 2 theories: • 1) Place Theory: says we hear different pitch b/c different sound waves trigger activity in different places along the cochlea’s membrane -so the brain determines pitch by recognizing the place on the membrane from which it receives neural signals… EX: hi freq. = beginning of membrane; lo = end --good at explaining high pitch, not so good at low • 2) Frequency Theory: the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch --EX: If freq. = 100, then 100 pulses per sec. travel up the auditory nerve…but above 1000? It can’t do it… --but volley principle says can alternate firing (like soldiers reloading)… -Freq. theory is good for low, not so good for high...so both together seem to explain it all…

44. How We Locate Sounds…& the “sound shadow”…Brain senses waves faster in closest ear & senses direction…loss of 1 ear = difficulty locating direction of sounds

45. Audition: Hearing loss • Conduction Hearing Loss: hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea • Hearing aids can help; sometimes can be surgically repaired • Nerve Hearing Loss (Sensorineural) : hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve • Cilia (receptor cells for hearing on basilar membrane) are damaged…& as of now you cannot repair this loss, & hearing aids are of minimal benefit • Usually caused by exposure to loud sound or to constant sound …and also by aging --can be caused by some diseases also

46. Hearing Loss: Repairing sensori-neural hearing loss: -hearing aids may help a bit -regenerating cells in other animals (sharks, birds) led to in other animals—guinea pigs & rat pups -scientists hope to be able to do the same in humans -can do a cochlear implant, a “bionic ear”, that does get some sound info to the brain -can use on adults who lost hearing later & on deaf kids…but not on adults who lost hearing as a young child & didn’t learn to process sound Deaf Culture: some members of Nat. Assoc. of the Deaf argues you should not do this to kids…that deafness is NOT a disability… Read p. 217…make a few notes about this (both sides of the argument) …what do you think? And we will discuss this…

47. Cochlear implants

48. Amplitude required for perception relative to 20-29 year-old group 1 time 10 times 100 times 1000 times 32 64 128 256 512 1024 2048 4096 8192 16384 Frequency of tone in waves per second Low Pitch High Audition & ages… • Older people tend to hear low frequencies well but suffer hearing loss for high frequencies • navy line = 20-29; red = 30-39; blue= 40-49; green = 50-59; yellow = 60+

49. Touch: Though vision & hearing = 2 major senses for humans, others are critical also major • 4 Skin Sensations • pressure • only skin sensation with identifiable receptors • warmth • cold • Pain --these 4 processed w/ specialized nerve endings for each -emotional ties thru touch as well as survival (babies?) Why can we not tickle ourselves? 

50. Two different views of the sense of touch: