Chapter 5 Perception and Reality

1. Chapter 5 Perception and Reality McElhaney

2. IV. Sensation and (7–9%) Thresholds Sensory Mechanisms Sensory Adaptation Perception Attention Perceptual Processes Threshold Absolute Threshold Difference Threshold Physical, Psychological, and physiological variables affected by thresholds Signal Detection Theories Absolute Threshold Theory Sensory Receptors Transduce of energy for nervous system Anatomy, Function, Eye and ear Color theories of vision Audition Perceptual acuity Sensory adaptation Sensory disorders Deafness Colorblindness AP Outline

3. 5 senses work similarly: Select Analyze Filter Process identifies meaningful information. Sensation = Data Reduction System Information

4. All of the Senses: • Use Transduction: • The process of changing energy (stimulus) to a form that can be processed by the nervous system- • For example- light to a form that can be recognized by the retina.

5. Sensory Analysis • As senses process information (from environment) • The senses divide the world into perceptual features- or basic stimulus patterns • Example: • Vision features include: lines, shapes, edges, spots, colors

6. Fig. 5.1 Visual pop-out. (Adapted from Ramachandran, 1992b.) Pop-out is so basic that babies as young as 3 months respond to it (Quinn & Bhatt, 1998) Perceptual Feature

7. Sensory Coding • After sense info is analyzed • It is converted to neural messages –able to be understood by the brain.

8. Eyes Ears Tongue Nose Skin The type of sensation you experience Depends on which brain area is activated Vision Auditory Taste Touch Sense Organs and Sense Localization

9. All of the Senses include Concept of • Absolute Threshold: • The minimum amount of energy necessary for sensation to occur. • This is after transduction- • Immediate response in the brain • Recall limits of senses: Dog whistles- humans do not have awareness because they are below the minimum threshold of human awareness. • 40,000 hertz (hertz = vibrations per second)

10. Difference Thresholds and JND • Q: How much must a stimulus change before it is noticeably different? • JND= Just Noticeable Difference • Just Noticeable Difference= the change in stimulus intensity to be noticed between being noticed and not noticed. • Weber’s Law:The amount of change needed to produce a constant JND is a constant proportion of the original stimulus intensity (See page 178) 1 candle to increase need 10 more… (Web Site) • Relates to Sensitivity ratios -hearing is much more sensitive than taste.

11. Perceptual Defense • Thresholds vary for different people and can change • The resistance to perceiving threatening or disturbing stimuli = Perceptual Difference • We resist info that causes anxiety, discomfort or embarrassment

12. What is Subliminal Perception? • Limen= (threshold or limit) for awareness • Below the normal threshold= Subliminal • Krosnick Study- emotional images inserted too fast to be recognized- • Caused altered impressions • Not really effective in advertising. • Vokey and Read study for Rock Music- Back messaging (had no known effect) • Is Hypnopædia- Brave New World- is this Subliminal?

14. Lens Retina Cornea Fovea Optic Nerve Iris Pupil Blind Spot Aqueous Humor Vitreous Humor Ciliary Muscle Sclera Cones Rods Identify properties/function of Anatomy of the Eye:

17. Like a Camera Cornea (clear membrane- bends light inward) to focus images On a light sensitive layer Back of closed space = layer of photo-receptors In Retina (thick as postage stamp) Muscles alter shape of lens = focus Accommodation is another name for changing distance >-(----) >-(->-) Structure of Eye

19. Iris controls amount of light entering eye Colored Muscle that expands and contracts Changes size of pupil Dilation= enlarge Constriction= narrow Structure of the Eye Virtuous Humor- Jelly like substance fills the eyeball

20. Vision • Depends on Wavelength= the Visible spectrum (Electromagnetic energy the eyes respond to)

21. Vision • Wavelength = ? • Visible light starts @ 400 nanometers = one billionth of a meter = purple or violet • Long light waves= blue, green, yellow, orange, and red = 700 Nanometers • Hue= basic color categories- Red, orange, yellow, green, blue, Indigo, violet -> correspond to light’s wave lengths • Saturation= pure color= narrow band of light • Brightness-amplitude, height of light waves- taller • More energy = more color, brighter more intense.

23. The Retina • Retina is located at the back of the eye • Light is focused on to the retina----then sensation- is received by receptors in the retina--to the optic nerve. • Photo-receptor cells= Rods and Cones Fovea- cup shape, on retina, only has cones, greatest visual Acuity- or sharpness • Blind Spot- where optic nerve leave the eye-

24. 100 million in each eye Can not detect color Black and white =pure rod vision More sensitive to light Allow sight in dim-light Sensitive to movement Peripheral vision 6.5 million in each eye Work best in bright light Color sensation Fine detail Mostly center of eye Fovea contains only cones Most sensitive to yellow and green color Rods and Cones

25. Fig. 5.8 Experiencing the blind spot. (a) With your right eye closed, stare at the upper right cross. Hold the book about 1 foot from your eye and slowly move it back and forth. You should be able to locate a position that causes the black spot to disappear. When it does, it has fallen on the blind spot. With a little practice you can learn to make people or objects you dislike disappear too! (b) Repeat the procedure described, but stare at the lower cross. When the white space falls on the blind spot, the black lines will appear to be continuous. This may help you understand why you do not usually experience a blind spot in your visual field.

26. Peripheral Vision • Side vision- area outside Fovea • Rod vision- not very sharp-

27. LASIK- Lasor Assisted Insitu keratomileusis Reshapes and stretches the cornea Increases degree of cornea bending light

28. Vision Problems • Hyperopia: Difficulty focusing nearby objects (farsightedness) eye is too short- • Myopia: Difficulty focusing distant objects (nearsightedness) • Astigmatism: Cornea, or lens defect that causes some areas of vision to be out of focus; relatively common-lens not symmetrical • Lenses correct vision by changing the path of light

29. 20/20 • Visual Acuity = Sharpness • Normal 20/20 • 20’ distance you can see what average people see at 20 ft. • 20/40 = you can only see at 20 feet what most people see at 40 feet • 20/200 = correct= legal blindness

30. Trichromatic- three types of cones each sensitive to Red, Green, and Blue color 3 visual pigments Fire nerve impulses @ different rates to produce color sensations Opponent Process Theory Vision analyzes color in either or messages Red or green Yellow or blue Black or white After Image- “OPT” Color Theories- what happens in the eye?

31. Visual sensations that persist after stimulus is removed– “seeing spots” Relates to Opponent Process Theory- Fatigue caused by one response causes after image of opposite color system Both theories apply Tri-color 3 visuals Pigments= light sensitive chemicals Red, Green, or Blue 3 types of cones- Fire nerve impulse@ different rates to produce color sensations After Images

32. Mechanical View of Color Sensation • Colors are influenced in the brain by other colors nearby • = Simultaneous color contrast • Affect perception of color (p 186)

33. Colorblindness Ishihara Test • Cannot perceive colors • Lacks cone or cones don’t function • Rare • Genetic- Affecting Red and Green + Blue pigments in Cones • Color weakness people can’t see certain colors • 8% of males, 1% of women- see red-green as yellow and brown

34. Dark Adaptation • Increased retinal sensitivity to light after entering the dark; • similar to going from daylight into a dark movie theater • Rhodopsin: Light-sensitive pigment in the rods; involved with night vision • Night Blindness: Blindness under low-light conditions; hazardous for driving at night

35. Pixel • Dot of light • More pixels = sharper image

36. Hearing • Uses Data Reduction • (Select, Analyze, Filter info) • Stimulus for hearing = Waves • Vibrating objects = sound waves (rhythmic movement of air molecules) • Peaks = compression • Valleys = rarefaction • Frequency of sound waves= # waves per/sec (Corresponds to) Pitch= tone of the a sound

37. Amplitude • Amplitude = height of sound wave • Tells how much energy it contains • Relates to loudness (sound intensity)

38. Pinna Tympanic membrane Auditory Ossicles Malleus Incus Stapes Cochlea Corti Steriocilla Auditory nerve fiber Anatomy of Audition Sound waves are converted to nerve impulses through the Auditory System

42. Frequency Theory As pitch increases-nerve impulses of same frequency are fed to auditory nerve Example-> 800 hertz tone= # of vibrations per second= 800 nerve impulses per second Place Theory Higher and lower tones excite specific areas of the cochlea Hair cells respond to area greatest movement Audition Theories

43. Conduction Deafness Transfer vibration to inner ear is weak Ear Drum or Ossicles are damaged Hearing Aid makes sounds clearer and louder Nerve Deafness- damage to hair cells or auditory nerve Stimulation Deafness Loud sounds damage hair cells in Cochlea 85 decibels may cause permanent loss Temporary Threshold shift Partial/transitory hearing loss @ 120 decibels 2 Types of Deafness

44. Inner Ear Associated with motion sickness Sense organs for balance (Fluid in the inner of the ear) Vestibular System Fluid filled sacs- sensate movement, acceleration, & gravity

45. Receptors

46. Motion Sickness and Vestibular System • = Sensory Conflict Theory • When sensations from vestibular system don’t match sensations from eyes and body = conflict • Causes motion sickness • Why? • Evolution- poisons attack vestibular system-body reacts with nausea

47. Olfaction • Again- uses • Is a chemical sense (receptors that respond to chemical molecules) • Data Reduction & Transduction- • Airborne Molecules contact receptor cells in nose. • 5 million nerve fibers in nasal passages Axons go directly to olfactory bulbs in brain To olfactory cortex & limbic system.

48. Anosmia • Defective sense of smell for single odor • Suggests these are specific receptors for specific odors • 1 person in a hundred can’t smell

50. Smell Receptors • Shape of receptors impacts smells • Lock and key theory- some odors have specific shapes that fit receptors • # of activated receptors tells how strong an odor is… • Scent likes and dislikes are learned