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Sensation and Perception

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1 Sensation and Perception

2 Sensation and Perception
How we detect physical energy from the environment and encode it into neural signals that the brain interprets as sound, odor, taste, pain, and visual images Perception The process that makes sensory patterns meaningful; draws heavily on memory, and emotion Transduction the conversion of physical energy (light, vibration) into a neural message by neural receptors within a sense organ

3 Sensation Sensory Adaptation Absolute threshold Difference threshold
Diminished responsiveness of sensory systems due to prolonged stimulation (if it does not change; the sensation shifts to the background of our awareness) Absolute threshold The minimum stimulation necessary to detect light, sound, pressure, taste, and odor Difference threshold The smallest physical difference between 2 stimuli that can be recognized as a difference Difference threshold = JND (just noticeable difference)

4 Sensation Weber’s Law Fechner’s Law Steven’s Power Law
Difference threshold from individual to individual JND is proportionate to the intensity of the stimulus (high when the stimulus is HIGH; low when the stimulus is LOW) “what is SUBliminal to me may be SUPRAliminal to you” Fechner’s Law The magnitude of a stimulus estimated by a formula Steven’s Power Law A revision of “Fechner’s Law”

5 Signal detection theory Subliminal messages
Predicts when we will detect weak signals contingent upon the number of “false hits” Subliminal messages Refers to stimuli presented beneath or near absolute threshold that is strong enough to affect a sense organ but WITHOUT conscious awareness Ex. Tapes advertised help “stop smoking” or “lose weight” during sleep No evidence that subliminal messages are effective

6 Vision Retina Cornea Lens Iris Fovea
Light sensitive layer of cells in the back of the eye; the organ of transduction which converts light into a neural message Cornea Protective layer of the eye that covers the pupil and iris Lens Focuses the rays of light into an image onto the fovea Iris The colored muscle surrounding the pupil Fovea The section of the retina where images are focuses by the lens

7 Human eye

8 Vision Photoreceptors
Light sensitive cells that convert light to neural energy RODS (120 million) photoreceptors that are sensitive to dim light but NOT color CONES (6 million) photoreceptors that are sensitive to color Cones that are concentrated in the center of the retina that gives us the sharpest vision is an area called the FOVEA

9 Table 5.1 Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

10 Other eye structures Bipolar cells
Collect impulses from photoreceptors and sends them to the ganglion cells Bundles of ganglion cells make up the optic nerve Optic nerve transports visual info from the eye to the brain Light goes NO further than the retina Blindspot The point on the eye where the optic nerve exits the eye and there are NO photoreceptors


12 Visual cortex Transforms neural impulses into visual sensations of color, form, boundry and movement Takes 2 dimensional patterns from each eye and assembles them into our 3 dimensional world Combines memories, emotions motives and body position with touch to create a visual world

13 Color Wavelength = color Amplitude = brightness Brightness
Intensity of light, how much light reaches the retina Color or hue does NOT exist outside of the brain Our brain creates color based on the wavelength of light striking our eyes Eye detects visible light (pure energy same as x-rays, microwaves, UV rays) We have no biological receptors sensitive to other portions of the EM (electromagnetic) spectrum

14 Figure 5.4 The spectrum of electromagnetic energy Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

15 Color Red--------- longer waves Yellow/green--------- medium waves
Blue  short waves Opponent-process theory Bipolar cells process color in either or complementary pairs Red/green Yellow/blue the sensation of one inhibits the sensation of its opponent Trichromatic theory Different types of cones sense different parts of the light spectrum


17 Figure 5.5 Differing eyes Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

18 Dysfunctions of the eye
Color blindness Inability to distinguish color Most common type of color blindness is RED/GREEN More common is color weakness Cant distinguish pale colors ie pink and tan Nearsightedness Images and light are projected in FRONT of the retina creating a blurry image Farsightedness Images and light are projected BEHIND the retina

19 Figure 5.8 (a) Normal vision (b) Nearsighted vision (c) Farsighted vision Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

20 Hearing The transduction of air pressure waves into neural messages is called audition Strength of the sound wave determines LOUDNESS The length determines FREQUENCY From frequency we can determine PITCH Long waves have low frequency and low pitch Short waves have high frequency and high pitch Decibels are the measuring unit for sound Absolute threshold for sound is zero decibels

21 Ear drum (tympanic membrane) Middle ear Cochlea
Outer ear (pinna) Channels sound waves through the auditory canal Ear drum (tympanic membrane) The membrane that vibrates the waves Middle ear Transmits the vibrations:-- piston Cochlea Snail shaped tube of the inner ear, the vibrations cause the cochlea’s membrane (oval window) to vibrate; jostling the fluid This movement causes ripples in the basilar membrane (lined with hair cells) -Hammer -Anvil -Stirrup

22 Figure Hear here: How we transform sound waves into nerve impulses that our brain interprets Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

23 Hearing Frequency the number of vibrations or cycles the wave completes in a given time (cycles per sec. or Hz) Amplitude the physical strength of the sound wave; decrease in volume = decreasing amplitude Audition Sound wave relayed to the inner ear

24 Science of Hearing Sound wave is relayed to the Outer ear (pinna)---
ear drum (tympanic membrane) ---- Vibrations are sent to 3 bones of the middle ear --- Cochlea (organ of hearing) Focuses vibrations in the basilar membrane --- Basilar membrane converts vibration to neural message-- Stirring of the hairs in the basilar membrane stimulate nerve endings-- Convert mechanical vibrations to neural activity-- Neural message travels to the auditory cortex VIA the auditory nerve

25 Sound Sound has 3 qualities
Pitch Loudness Timbre Sound frequency determines the highness or lowness of PITCH Place theory Different frequencies activate different locations on the basilar membrane Frequency theory Neurons on the basilar membrane respond at different rates for different sound frequencies

26 Sound More intense sound waves produce louder sounds
The quality of sound waves refer to the timbre (sound recognition) Sound as a physical phenomenon DOES NOT EXIST Sound is purely a psychological sensation that requires an ear to produce it

27 Deafness Conductive deafness Nerve deafness
The ways sound waves are converted to nerve energy is interrupted Usually due to damage to the structures of the middle ear Due to trauma or over stimulation Nerve deafness Impulses from the oval window are sent to the brain Damage to the auditory nerve or higher processing centers People are usually born deaf

28 Smell Your sense of smell is referred to as OLFACTION
Odors-- receptor proteins associated with specialized hairs in the nose --- olfactory bulbs in the brain Olfactory bulbs located in the underside of the brain below the frontal lobes

29 Smell Smell does NOT go through the thalamus
Smell has a connection to memory Smell is also linked to communication ie PHERMONES Phermones are chemical signals released by organisms of the same species to signal: Receptivity Danger Territorial boundry Food sources

30 Taste Taste + smell = cooperative relationship subtle distinctions in taste are usually attributed to smell Sense of taste = gustation Sweet Bitter Sour Salty umami

31 Taste Umami --- asian cuisine Taste receptors gathered in taste buds
MSG (monosodium glutamate) Taste receptors gathered in taste buds Top and side of tongue Receptors cluster in papillae Individuals vary in their sensitivity to taste Taste is linked to the somatosensory cortex of the parietal lobe Super-sensitivity of your sense of taste decreases as you age

32 Taste Taste buds are damaged by alcohol, smoke, acids, or hot foods
Your sense of taste is the MOST resistant to permanent damage There is a constant renewal of your taste receptors

33 Touch Touch is a mix of 4 different skin senses
Pressure Warmth Cold pain The skin has different specialized nerve endings that are sensitive to each BUT only pressure has identifiable receptors Cold + warm = burning HOT Cold metal = wetness

34 Touch Phantom limb sensations
The brain anticipates receiving stimulation from a limb that does not exist The brain can sense without functioning senses

35 Pain Pain tells us something is wrong with the body
People born without pain receptors usually die early Unchecked infections Joint failure Chronic pain (an alarm that wont stop ringing) Headaches Backaches Arthritis hyperalgesia Gate control theory for PAIN The spine either blocks or allows pain to go to the brain Small nerve fibers conduct pain signals Large nerve fibers conduct other signals of stimulation

36 Pain Tissue is injured:
in small fibers activate opening the “gate” = PAIN Large fibers close the “gate” turning PAIN off Many treat chronic pain by stimulating the gate closing activity of the large fibers Massage acupuncture electric stimulation

37 PAIN The brain can also “psych” itself out by distracting itself from the pain by focusing on something else (ex. Athletes) Pain Management Lamaze is a combination of: Relaxation (breathing) + Counter stimulation (massage) + distraction (visualize a comfortable environment or counting backwards)

38 Figure Biopsychosocial perspective on pain Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

39 Bottom Up processing Top Down processing
Working up from sensory receptors to higher levels of processing Top Down processing Refers to constructing perceptions on sensations from “bottom up” processing, experience, and expectations

40 Figure 5.1 Sensation and perception: One continuous process Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

41 Sensory compensation and Sensory interaction
People who lose 1 sense do seem to compensate with a slight enhancement of other sensory abilities closing eyes during kissing minimizes distractions and increases sensitivity Sensory interaction Where one sense influences another Ex. Taste + smell + texture = FLAVOR

42 Perception Perception = top down processing
Sensation = bottom up processing Selective Attention where our awareness focuses on a limited aspect of what we experience Ex. Cocktail party effect- focus on 1 voice ignoring many Inattentional blindness Where your attention is focused on 1 thing; you fail to see visual objects Change blindness, deafness, choice blindness Humans focus so strongly on a list or chore they ignore change in stimuli. Visual capture When our senses send info that competes or conflicts with what we see VISION DOMINATES

43 Unnumbered 6.2 Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

44 Unnumbered 6.3 Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

45 Unnumbered 6.4 Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

46 Unnumbered 6.5 Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

47 Perception Gestalt (form or whole) Form Perception
How we organize our sensations into perceptions Form Perception Figure/ground Figure is what you focus on Ground is what you ignore Words (figure) Blackboard (ground)

48 Grouping- helps us construct reality but can lead our perception awry
Proximity- tendency to group figures that are nearby together Similarity- tendency to group similar objects together Continuity- tendency to perceive smooth, continuous patterns rather than discontinuous ones Connectedness- connected = whole and 1 Closure- fill in gaps to create a whole

49 Figure 6.6 Organizing stimuli into groups Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

50 Unnumbered 6.6 Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

51 Figure 6.7 Grouping principles Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

52 Depth Perception Seeing objects in 3D= depth perception and enables us to gauge distance Visual cliff and babies perceive depth Binocular cues- Judging the distance of nearby objects Retinal disparity The difference between the two images received from the eyes Convergence The extent in which the eyes converge inward when looking at an object. Greater the strain the closer the object

53 Figure 6.8 Visual cliff Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

54 Figure 6.9 The floating finger sausage Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

55 Monocular cues- gauging distance (10ft away or 100 ft away)
Relative size- perceive the object that casts a smaller retinal image to be further away Interposition- if one object blocks our view of another we perceive it as closer Relative clarity- we perceive hazy objects as further away Texture gradient- indistinct texture signals increase distance Relative height- higher objects in our field of vision are perceived to be further away Linear perspective two parallel lines converge they appear further away Light and shadow- nearby objects reflect more light than faraway objects Relative motion-

56 Light and shadow

57 interposition

58 Texture gradient

59 Figure Perspective techniques Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

60 Relative motion

61 Motion perception Phi phenomenon- blinking lights being perceived as one light moving (ex. A marquee)

62 ESP ESP- extrasensory perception
Telepathy- reading someone’s mind or projecting ones thoughts Clairvoyance- perceiving remote events Precognition- seeing events before they happen Psychokinesis- telekinesis (moving an object with your mind) Test a ESP’er to see if it works Reproducible phenomena and theory to explain


64 Perceptual Constancy Refers to how we recognize an object despite different angles, sizes, distance or illumination Because of this we perceive objects as unchanging Shape constancy Size constancy Lightness constancy Color constancy

65 Figure 6.13 Shape constancy Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

66 Perceptual set The mental predisposition to perceive one thing and not another Schemas influence our perceptual set Schemas are formed through our experience

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