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Perception and sensation

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Sensation and perception
Sensation and perception
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Perception and sensation

  2. 2. Sensation: Receiving Messages About the World <ul><li>Sense organs </li></ul><ul><ul><li>See, hear, taste, smell, touch, balance, and experience the world </li></ul></ul><ul><ul><li>Sensory receptor cells transmit sensation </li></ul></ul><ul><ul><li>Perception – interpreting information and forming images </li></ul></ul><ul><ul><li>Stimulus </li></ul></ul>Sensation and Perception
  3. 3. Translating Messages for the Brain <ul><li>Transduction – translates one form of energy (incoming stimuli) into another (sensory information) </li></ul><ul><ul><li>Receptor cells to neural impulses </li></ul></ul>Sensation and Perception
  4. 4. Sensory Limits: How Strong Must Messages Be? <ul><li>Threshold – lower limits </li></ul><ul><li>Absolute threshold – smallest to be detected </li></ul><ul><li>Difference threshold – smallest difference between 2 stimuli to be detected 50% of time </li></ul><ul><li>Sensory adaptation – one’s sensitivity to a stimulus varies from time to time </li></ul><ul><ul><li>Fatigue, inattention, repeated exposure </li></ul></ul>Sensation and Perception
  5. 5. Sensory Thresholds Vision A candle flame seen at 30 mi. on a clear, dark night Hearing The tick of a watch under quiet conditions at 20 ft. Taste One teaspoon of sugar in 2 gallons of water Smell 1 drop of perfume diffused into the entire volume of a 3 room apartment Touch The wing of a bee falling on your cheek from a height of 1 cm
  6. 6. Sensory Limits: How Strong Must Messages Be? <ul><li>Weber’s law – amount of change needed for detection 50% of time is always in direct proportion to intensity of original stimulus </li></ul>Sensation and Perception
  7. 7. Stimulus – any from of energy capable of exiting the nervous system like light waves, sound waves, and the chemical energy that causes the sensation taste and smell. Receptor – is a specialized nerve ending capable of responding to energy. Senses – mechanisms which convert stimulus energy into neutral energy.
  8. 8. *Five Human Senses* 1.VISION The organ for vision is the eye. It is stimulated by light waves that strike the retina where the photo-sensitive cells- the rod and the cones- are located. The rods and cones are the receptor for vision.
  9. 9. Parts of Human Eye
  10. 10. <ul><li>Structure </li></ul><ul><li>Globe - shaped and has a diameter of approximately one inch. </li></ul><ul><li>Composed of three coats: </li></ul><ul><li>Sclera - the outer layer, a tough opaque layer of connective tissue used to protect the inner structures of the eye. Helps maintain the shape of the eyeball, in front, this layer becomes the cornea which is thin and transparent. </li></ul>
  11. 11. Choroid Coat - the middle layer, a pigmented layer. It contains some of the blood vessels that supply the eye with blood. It also absorbs imperfectly focused light rays. In the front part of the eye, it becomes modified to from the iris and the cilliary blood. Pupil – the central opening of the iris
  12. 12. Iris – a circular arrangement of muscles that contract and expand to change the size of the pupil depending upon the intensity of illumination called light or dark adaptation. The color of the eye is due to the pigment in the iris Accommodation – the process when the lens become thinner to bring faraway objects into focus and thickens to focus on nearly objects.
  13. 13. Vision: Sensing Light <ul><li>Light </li></ul><ul><ul><li>Electromagnetic radiation </li></ul></ul><ul><ul><ul><li>Waves - frequency </li></ul></ul></ul><ul><ul><ul><li>Wavelength – determines hues seen </li></ul></ul></ul><ul><ul><ul><li>Intensity – brightness </li></ul></ul></ul><ul><ul><li>The more wavelengths in light, the less saturated or pure its hue is </li></ul></ul>Sensation and Perception
  14. 14. The Eye: How Does It Work? <ul><li>Light passes through cornea </li></ul><ul><li>Iris regulates light through pupil into lens </li></ul><ul><li>Lens held in place by ciliary muscle </li></ul><ul><li>Retina has rods and cones for receptors Fovea – center of retina </li></ul><ul><li>Visual acuity – clarity and sharpness </li></ul>Sensation and Perception
  15. 15. Photoreceptors Cones Rods
  16. 16. The Eye <ul><li>Rods </li></ul><ul><ul><li>Not located in fovea </li></ul></ul><ul><ul><li>Responsible for peripheral vision </li></ul></ul><ul><ul><li>Hundreds of times more sensitive to light than cones </li></ul></ul><ul><ul><li>Produce images perceived with less visual acuity than cones </li></ul></ul><ul><ul><li>Do not detect color </li></ul></ul>Sensation and Perception
  17. 17. The Eye <ul><li>Cones </li></ul><ul><ul><li>Give brain more precise information </li></ul></ul><ul><ul><li>Code information about color </li></ul></ul><ul><ul><li>Respond only in bright light </li></ul></ul><ul><li>Optic nerve – has no cones or rods </li></ul><ul><li>Blind spot – no visual reception in optic nerve </li></ul><ul><li>Optic chiasm </li></ul>Sensation and Perception
  18. 18. Dark and Light Adaptation <ul><li>Dark adaptation </li></ul><ul><ul><li>Receptors receive new supply of chemicals </li></ul></ul><ul><ul><li>After 30 minutes in the dark - level of sensitivity about 100,000 times greater than in bright light </li></ul></ul><ul><li>Light adaptation </li></ul><ul><ul><li>Rods and cones highly responsive – overload </li></ul></ul><ul><ul><li>Bleaching out of receptor chemicals occurs </li></ul></ul>Sensation and Perception
  19. 19. <ul><li>Defects of Vision </li></ul><ul><li>Presbyopia </li></ul><ul><li>– a special form of farsightedness which occurs with advancing age. The presbyopic person cannot focus clearly on near objects. </li></ul>
  20. 20. Presbyopia
  21. 21. <ul><li>Farsightedness or Hyperopia </li></ul><ul><li>– is caused by a shortened eyeball, making the distance from the lens to the retina too short. The lens will focus at a point behind the retina. A farsighted person is able to see far objects clearly but not near ones. </li></ul>
  22. 23. <ul><li>Nearsightedness or Myopia – near objects are not seen clearly but lens is unable to thin enough to bring far objects into clear focus. </li></ul>
  23. 24. <ul><li>Astigmatism </li></ul><ul><li>– a structural defect of the eye generally caused by an irregularity in the shape of the cornea. </li></ul>
  24. 25. Color Blindness <ul><li>Affects about 8% of males, 1% of females </li></ul><ul><li>Partial color blindness – difficulty distinguishing between two colors </li></ul><ul><ul><li>Red-green blindness due to genetic defect </li></ul></ul><ul><ul><li>Yellow-blue blindness due to absence of blue pigment in cones </li></ul></ul>Sensation and Perception
  25. 26. <ul><li>Colorblindness </li></ul><ul><li>– Poor color vision can be cause by an inherited lack of one or another of the three types of cones. </li></ul>
  26. 27. Color Blindness
  27. 28. <ul><li>2. HEARING </li></ul><ul><li>It is the most vital channel of interaction with the environment. </li></ul><ul><li>The stimuli fro hearing are soundwaves. </li></ul><ul><li>Three dimensions describing the sound stimulus are : </li></ul><ul><li>Intensity </li></ul><ul><li>Frequency </li></ul><ul><li>Complexity </li></ul>
  28. 30. Hearing: Sensing Sound Waves <ul><li>A udition - detection of sound waves </li></ul><ul><li>Frequency of cycles </li></ul><ul><ul><li>Compression – increased density of waves </li></ul></ul><ul><ul><li>Rarefaction – reduced density of waves </li></ul></ul><ul><ul><li>Determines pitch of sound </li></ul></ul><ul><ul><li>Intensity measured in decibel (db) units </li></ul></ul><ul><ul><ul><li>Prolonged exposure to over 85 db causes hearing loss </li></ul></ul></ul><ul><ul><li>Timbre – quality of sound </li></ul></ul>Sensation and Perception
  29. 31. Maximum level of industrial noise considered safe Characteristics of Sound Waves 20 40 60 80 100 160 0 120 180 140 Loud thunder or rock concert Pain Threshold City bus Normal conversation Subway db Noisy automobile Absolute threshold of human hearing Quiet office Whisper Rocket launch
  30. 32. Structure of the ear. The ear is divided into three parts: The outer ear - it is the visible part of the ear, composed of the pinna, the auditory canal, and the tympanic membrane commonly called eardrum.
  31. 34. The middle ear – an air- filled chamber that is connected to the pharynx by the eustachian tube.
  32. 35. This connection of the middle ear to the pharynx serves to equalize the pressure on the two sides of the eardrum. The middle ear structure is composed of tree small bones or ossicles: the mallleus (hammer), the incus (anvil), and the stapes (stirrup). These bones are hanging into the system of levers, so that the movement of the eardrum is transmitted to a membrane called the oval window.
  33. 36. The inner ear – can find a cochlea which is a fluid- filled bony structure shaped like a snail shell. It is the organ of hearing. There are three canals in the cochlea–the cochlear canal, the tympanic canal, and the vestibular canal.
  34. 38. The Ear: How Does It Work? <ul><li>Outer ear </li></ul><ul><ul><li>Pinna – external part of ear that collects sound </li></ul></ul><ul><ul><li>External auditory canal – connects outer and middle ear </li></ul></ul><ul><li>Middle ear </li></ul><ul><ul><li>Cardum – tympanic membrane; 1st structure </li></ul></ul><ul><ul><li>Eardrum - outermost structure of middle ear </li></ul></ul><ul><ul><ul><li>Passes vibration to interconnected bones ( hammer , anvil , and stirrup ) </li></ul></ul></ul>Sensation and Perception
  35. 39. The Ear: How Does It Work? <ul><li>Inner ear </li></ul><ul><ul><li>Oval window – eardrumlike structure at end of cochlea </li></ul></ul><ul><ul><li>Round window – eardrumlike structure at other end of cochlea </li></ul></ul><ul><ul><li>Basilar membrane – forms floor for ear’s sensory receptors </li></ul></ul><ul><ul><li>Organ of Corti – contains hairlike receptor cells </li></ul></ul>Sensation and Perception
  36. 40. <ul><li>Hearing Defects </li></ul><ul><li>Conduction Deafness – deafness due to inability to transmit vibrations through the external and middle ear. </li></ul><ul><li>Nerve Deafness – this kind of deafness results from damage to the nerves themselves or to the delicate parts of the cochlea. </li></ul>
  37. 41. 3. SMELL - The receptors for smell are found at the olfactory epithelium located at the very top of the nasal passages. -They are sensitive only to gases and to volatile substances that have been dissolved in the air.
  38. 42. Parts of Human Nose
  39. 43. 4. TASTE Much of the sensation depends on other factors-on warmth, coldness, the mild irritation caused by certain spices, and above all, on smell. When our nostrils are stuffed because of colds. Food seems almost tasteless. The tastebuds are the receptors for taste. They respond to four qualities of taste: sweet, sour, salty, and bitter.
  40. 44. Chemical Senses: The Flavors and Aromas of Life <ul><li>Senses of gustation (taste) and olfaction (smell) differ from all other senses </li></ul><ul><ul><li>Taste cells and papillae on tongue </li></ul></ul><ul><ul><li>Taste buds detect </li></ul></ul>Sensation and Perception Sweetness - mostly sugars Sourness - mostly acids Saltiness - mostly salts Bitterness - toxins, chemicals Fattiness - fats
  41. 45. Parts of Human Tongue
  42. 46. Taste Surface of tongue Receptor cells Pore Bitter Sour Salty Sweet and fatty Sensory nerve fiber
  43. 47. Chemical Senses: The Flavors and Aromas of Life <ul><li>Olfaction </li></ul><ul><ul><li>Olfactory epithelium – top of nasal cavity </li></ul></ul><ul><ul><li>Pheromone detection of sweat and urine </li></ul></ul><ul><ul><ul><li>Vomeronasal organ </li></ul></ul></ul><ul><ul><ul><li>Influence human female reproductive cycles </li></ul></ul></ul><ul><ul><ul><li>Inhalation of male sex hormone and mood changes </li></ul></ul></ul><ul><ul><ul><li>Males may respond to sex hormones </li></ul></ul></ul>Sensation and Perception
  44. 48. Olfactory nerve to brain Olfactory epithelium Nasal cavity
  45. 49. 5. THE SKIN SENSES The skin has four separate senses: pain, pressure, cold, and warmth. The receptors fro the skin senses are nerve endings which come in four general forms: free nerve endings, globular bulbs, egg- shaped corpuscles, and “baskets” surrounding root hairs.
  46. 50. Parts of Human Skin
  47. 51. Body Sensations: Messages About Myself <ul><li>Orientation and movement </li></ul><ul><ul><li>Vestibular organ – 2 sets of sensory structures </li></ul></ul><ul><ul><ul><li>Semicircular canals </li></ul></ul></ul><ul><ul><ul><li>Saccule and utricle </li></ul></ul></ul><ul><ul><li>Kinesthetic receptors – throughout body </li></ul></ul><ul><li>Skin senses </li></ul><ul><ul><li>Pressure sensitivity </li></ul></ul><ul><ul><li>Temperature sensitivity </li></ul></ul>Sensation and Perception
  48. 52. The Skin Senses Pressure Free nerve endings Tactile discs hair Specialized end bulbs basket cell around hair Temperature
  49. 53. Pain <ul><li>Nerve endings in body act as nocioceptors </li></ul><ul><ul><li>Neural messages transmitted along two distinct pathways </li></ul></ul><ul><ul><ul><li>Rapid – detects first pain sensation </li></ul></ul></ul><ul><ul><ul><li>Slow – detects second long-lasting pain </li></ul></ul></ul><ul><ul><li>Endorphins and endogenous morphine </li></ul></ul>Sensation and Perception
  50. 54. Pain <ul><li>Nerve endings in body act as nocioceptors </li></ul><ul><ul><li>Pain gates regulate pain signals in 3 areas </li></ul></ul><ul><ul><ul><li>Brain stem – gate-control theory of pain </li></ul></ul></ul><ul><ul><ul><li>Spinal cord </li></ul></ul></ul><ul><ul><ul><li>Peripheral regulation of pain </li></ul></ul></ul><ul><ul><li>Phantom limbs </li></ul></ul><ul><ul><ul><li>Up tp 70% of amputees experience this </li></ul></ul></ul>Sensation and Perception
  51. 55. Gate-control theory of pain Direction of pain message neuro-transmitter molecules in axon of slow-pain neuron Endorphin receptor Axon of inhibitory pain gate neuron endorphin Neuron in slow-pain fiber Inhibitory pain gate neuron Stimulation of endorphin receptors inhibits firing of axon of slow-pain neuron Close-up view of inhibitory pain gates Somatosensory area of cortex Limbric system Area of pain gates Pathway of fast-pain fibers Pathway of slow-pain fibers
  52. 56. KINESTHESIS This is the sense of bodily movements. Its receptors are nerve endings found in muscles, tendons, and linings of joints. EQUILIBRIUM This is also called as the Static Sense. Two kinds of receptors give information about movements of the head and permit a sense of balance of the body.
  53. 57. These are in the semicircular canals and the vestibular canal. Both are located in the inner ear next to cochlea. THE ORGANIC SENSE This give s the result of the sensitivity of the visceral and other internal organs oft he body. Among the visceral organs are the stomach, intestines, sex structure, throat, hear and lungs.
  54. 58. PERCEPTION Chaplin defines perception as the process of knowing objects and objective events by means of senses. This sensory input consists of nerve impulses. They carry a sort of raw, undigested information about the environment. The individual must convert it into a meaningful information. Perception, then, is the organization of sensory input into meaningful experiences.
  55. 59. PERCEPTUAL CONSTANCY The perception of an object and all of its properties as constant and unchanging in spite of the continuously changing sensations of these properties outline the scope of object constancies. Our perceptual organization remains relatively stable even though some aspects of the pattern within the optical array undergo great changes.
  56. 60. <ul><li>ORGANIZATION IN PERCEPTION </li></ul><ul><li>Figure and ground – when we perceive an object, usually one part tends to stand out while the rest seems to remain in the background. The part which stands out is called the figure and the rest of the stimulus pattern is called the ground. </li></ul>
  57. 61. Figure and Ground
  58. 62. Laws of Perceptual Organization Figure-Ground
  59. 63. <ul><li>Grouping – we are concerned more with the figure than with the ground. </li></ul><ul><li>* The principles of similarity – stimuli which are similar tend to be perceived as forming a group. </li></ul>
  60. 64. Similarity
  61. 65. * The principle of proximity – there is a tendency to perceive stimuli which are near one another as belonging together.
  62. 66. *The principle of closure – when fragmentary stimuli form enough of a familiar figure, we tend to perceive the whole figure, ignoring the missing part of parts.
  63. 67. *The principles of continuity – stimuli which from a continuous pattern are perceived as a whole, the pattern they make generally appears as a figure apart from the ground.
  64. 68. ATTENTION AND PERCEPTION Perception is selective. The direction of perception toward selected objects is called attention. A number of stimulus conditions help determine the direction of attention
  65. 69. DEPTH PERCEPTION This is the ability to see three- dimensional space and accurately judge distances. A study of perception would be incomplete without considering perceiving the third dimension- distance and depth.
  66. 70. Depth Perception <ul><li>Retina has two-dimensional surface </li></ul><ul><li>Monocular cues – perception of one eye </li></ul><ul><ul><li>Texture gradient </li></ul></ul><ul><ul><li>Linear perspective </li></ul></ul><ul><ul><li>Superposition </li></ul></ul><ul><ul><li>Shadowing </li></ul></ul>Sensation and Perception <ul><ul><li>Speed of movement </li></ul></ul><ul><ul><li>Aerial perspective </li></ul></ul><ul><ul><li>Accommodation </li></ul></ul><ul><ul><li>Vertical position </li></ul></ul>
  67. 71. Depth Perception <ul><li>Binocular cues – perception with two eyes </li></ul><ul><ul><li>Convergence </li></ul></ul><ul><ul><li>Retinal disparity </li></ul></ul><ul><li>Visual Illusions </li></ul><ul><ul><li>Ponzo illusion </li></ul></ul><ul><ul><li>Vertical-horizontal illusion </li></ul></ul><ul><li>Color perception </li></ul>Sensation and Perception <ul><ul><li>Zollner illusion </li></ul></ul><ul><ul><li>Moon illusion </li></ul></ul><ul><ul><li>Poggendorf illusion </li></ul></ul>
  68. 72. Perception - Depth Perception
  69. 73. <ul><li>PERSONAL FACTORS IN PERCEPTION </li></ul><ul><li>Motives </li></ul><ul><li>Emotions </li></ul><ul><li>Attitudes </li></ul><ul><li>Frames of reference </li></ul>
  70. 74. <ul><li>ERRORS IN PERCEPTION </li></ul><ul><li>Illusion – a perception which is common but usually considered mistaken. This is an error which depends on stimulus conditions and occur in normal individuals. </li></ul><ul><li>Hallucinations – are false perceptions that occur under abnormal conditions. </li></ul>
  71. 75. 1.Illusions based on relative size.
  72. 76. 2. Illusions based on intersecting lines.
  73. 77. 3. Ponzo illusion.
  74. 78. Multisensory Integration <ul><li>Integrate and interpret information from multiple senses simultaneously </li></ul><ul><ul><li>Limited ability and accident occurrence </li></ul></ul><ul><li>Motivation, Emotion, and Perception </li></ul><ul><ul><li>Motivation and emotions influence perception </li></ul></ul><ul><li>Past experiences influence all perceptions </li></ul>Sensation and Perception
  75. 82. THE END Sensation and Perception

Notes de l'éditeur

  • There are approximately 125 million rods located outside the fovea which code information about light and dark. There are approximately 6 million cones, mostly located in the fovea, which code information about light, dark, and color. Role of rods and cones differ. 1. Rods are largely responsible for peripheral vision because of their location. 2. Rods are hundreds of times more sensitive to light, therefore, they play a more important role in vision in dim light. 3. Rods produce images that are perceived with less visual acuity than do cones. 4. Rods do not detect color as do cones.