Introduction to sensation and perception

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This slideshow was created with images from the web. I claim no copyright or ownership of any images. If a copyright owner of any image objects to the use in this slideshow, contact me to remove it. This is for a course in Introductory Psychology using Wayne Weiten's "Psychology: Themes and Variations" 8th ed. Published by Cengage. Images from the text are copyrighted by Cengage.

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Introduction to sensation and perception

  1. 1. Introduction to Sensation and Perception<br />Chapter 4<br />
  2. 2. How Psychology developed as a field.<br />The ways Psychologists conduct research.<br />The basic building blocks.<br />Genes, Nervous System, Hormones<br />Bringing the world into your brain.<br />Sensation and Perception<br />Chapter 1 –<br />Chapter 2 –<br />Chapter 3 –<br />Chapter 4 –<br />
  3. 3. Why Study Sensation and Perception?<br />“I’ll believe it when I see it”<br />“I know what I saw (heard)”<br />“How can you eat that!!”<br />“What do you mean, you like getting spanked?”<br />
  4. 4. Each of these, <br />at least at the most basic level, <br />involves sensation and perception.<br />
  5. 5. Two Main Points<br />Human sense organs are not like electronic equipment<br />Eyes are not cameras, Ears are not microphones…<br />There is variability in sensation<br />For different stimuli – sensation is relative<br />Perception is SUBJECTIVE, not absolute<br />
  6. 6. Sensation<br />Definition: stimulation of the sense organs<br />
  7. 7. Thresholds<br />Intuitive definition<br />The “threshold” of your house is your doorway. You’re outside until you pass through the threshold; then you are inside. This happens exactly at the door frame… every time… always the same…<br />Do your eyes work like that?<br />
  8. 8. Thought Experiment<br />You have a two-mile long garage with no windows <br />(pretend this isn’t ridiculous)<br />
  9. 9. Thought Experiment<br />Inside, you put a remote-controlled truck at one end. On top of the truck is an extremely tiny, faint light bulb. It has no other lights.<br />
  10. 10. Thought Experiment<br />You sit at the other end and turn off the lights. It’s pitch black.<br />You hold the remote stick to start the truck moving toward you, slowly. Release the control to stop the truck as soon as you see the light bulb.<br />Truck<br />You<br />
  11. 11. Thought Experiment<br />Turn on the lights. Go to the truck and mark a chalk line on the floor where it stopped.<br />Set up the truck again, turn off the lights. Start the truck. Stop it when you see the light. Mark the floor with chalk.<br />Repeat this 100 times<br />
  12. 12. Thought Experiment<br />If your vision had a threshold like a doorway in a house, you would draw a chalk line in the same spot on the floor every time – 100 lines all on top of each other.<br />That’s not what you get.<br />
  13. 13. Thought Experiment<br />Here is what the chalk lines on the floor would look like, approximately:<br />So where is the “threshold”?<br />Note: this is a simplification. The lines wouldn’t be symmetrical as drawn above, but explaining why needs physics and math. The example is valid despite this simplification. <br />
  14. 14. Thresholds<br />Operational definition of Threshold for light<br />The minimum amount of light at which you detect it 50% of the time.<br />In the thought experiment, it would be the point on the floor where 50% of the lines are in front of it, and 50% are beyond it.<br />So about right here<br />
  15. 15. If you graphed this, you would get the red curve.<br />Note: the intuitive definition of a threshold is the blue curve<br />
  16. 16. Truck getting closer<br />The horizontal axis is the distance of the truck from you.<br />When the light on the truck is far away, it is a very low intensity.<br />As the truck gets closer, the intensity of the light increases<br />(This is physics. Google the Inverse Square Law if you’re curious why this happens.)<br />
  17. 17. Think of the vertical axis as the percentage of the 100 chalk lines that the truck has crossed as it drives toward you.<br />
  18. 18. None<br />Think of the vertical axis as the percentage of the 100 chalk lines that the truck has crossed as it drives toward you.<br />
  19. 19. None<br />Think of the vertical axis as the percentage of the 100 chalk lines that the truck has crossed as it drives toward you.<br />
  20. 20. Couple<br />Think of the vertical axis as the percentage of the 100 chalk lines that the truck has crossed as it drives toward you.<br />
  21. 21. More<br />Think of the vertical axis as the percentage of the 100 chalk lines that the truck has crossed as it drives toward you.<br />
  22. 22. 50%<br />Think of the vertical axis as the percentage of the 100 chalk lines that the truck has crossed as it drives toward you.<br />
  23. 23. Most<br />Think of the vertical axis as the percentage of the 100 chalk lines that the truck has crossed as it drives toward you.<br />
  24. 24. All<br />Think of the vertical axis as the percentage of the 100 chalk lines that the truck has crossed as it drives toward you.<br />
  25. 25. So…<br />
  26. 26. Thresholds – Review and Main Points<br />Your eyes are not like cameras.<br />There is variability in how you sense light.<br />The intuitive idea of a “Threshold” simply does not fit.<br />We use an operational definition of “absolute threshold” to describe how you really notice a stimulus.<br />
  27. 27. Main Point 1. First Part<br />There is variability in sensation<br />
  28. 28. Just Noticeable Differences (JNDs)<br />Now that you see a light, how much does it have to change in intensity for you to notice it?<br />This is the JND<br />The size of the JND depends on how intense the first light is.<br />
  29. 29. Just Noticeable Differences (JNDs)<br />Example: <br />You have a bulb that lets you go from 5 Watts to 10 Watts.<br />You would see this difference.<br />10 W<br />5 W<br />
  30. 30. Just Noticeable Differences (JNDs)<br />But if you went from a 100 Watt bulb to a 105 Watt bulb, you would see no difference.<br />A difference of 5 Watts is only noticeable if you start with dim bulbs.<br />100 W<br />105 W<br />
  31. 31. Have you ever purchased a three-way bulb that goes from 50 Watts to 100 Watts to 150 Watts?<br />You see a big change from dark to 50W, then a large increase in brightness when you click to 100W….but there’s only a tiny change after the third click to 150W.<br />150 W<br />100 W<br />50 W<br />
  32. 32. This is a similar idea to JNDs. <br />The key point is that your eyes are not on an absolute scale. <br />What you notice is relative to stimulus intensity!<br />
  33. 33. Main Point 1. Complete<br />There is variability in sensation<br />For different stimuli – sensation is relative<br />
  34. 34. Perception<br />Definition: The selection, organization, and interpretation of sensory input<br />
  35. 35. Playing with a truck in a fictional building was fun, but that isn’t the real world.<br />The idea of an “absolute threshold” applies best to laboratories, or to silly situations like a two-mile long garage with no windows…<br />In the real world, it is more complicated.<br />
  36. 36. What if the survival of a plane full of people relies on you noticing this light as you look at this display<br />
  37. 37. Signal Detection Theory<br />Signal Detection Theory has direct applications in the design of many products.<br />In the case of cockpits, it is essential.<br />
  38. 38. Signal Detection Theory<br />Whether or not a pilot detects a warning light depends on:<br />Stimulus Intensity<br />the idea of absolute threshold still applies<br />If a light is too dim, the pilot doesn’t see it<br />Noise in the environment<br />“Noise” refers to stimuli competing for the same sense<br />In a cockpit, other lights, dials, flashes, and reflected lights are “noise”<br />More noise  more intense warning light is needed for detection<br />Your Criterion for Deciding if you detect the stimulus<br />
  39. 39. Signal Detection Theory<br />Here is where detecting a little warning light becomes a question of perception.<br />You select, organize, and interpret sensory information. <br />You matter.<br />
  40. 40. Signal Detection Theory<br />Good situation:<br />The pilot is vigilant, attentive, and motivated. He or she is concerned about doing the job well.<br />Bad situation:<br />The pilot feels comfortable flying, sees him or herself as a seasoned pro, and has the routine flight checklists so well learned that he or she can “do it in their sleep.”<br />
  41. 41. Signal Detection Theory<br />Good situation:<br />The pilot is vigilant, attentive, and motivated. He or she is concerned about doing the job well.<br />This is a very sensitive criterion<br />Bad situation:<br />The pilot feels comfortable flying, sees him or herself as a seasoned pro, and has the routine flight checklists so well learned that he or she can “do it in their sleep.”<br />This is not a sensitive criterion<br />
  42. 42. Main Point 2. <br />Perception is SUBJECTIVE, not absolute.<br />
  43. 43. Signal Detection Theory<br />Review – Detecting a stimulus depends on:<br />Stimulus Intensity<br />If a light is too dim, the pilot doesn’t see it<br />Noise in the environment<br />More noise  more intense warning light is needed for detection<br />The person’s criterion for deciding if they detect the stimulus<br />
  44. 44. Four Possible Outcomes<br />In a signal detection situation, there are four possible outcomes as you try to detect the stimulus.<br />Columns represent reality<br />Rows are the person’s decision.<br />
  45. 45. Example: You order a pizza during a party. As you enjoy yourself, there is background noise. You are listening for the doorbell for the pizza person.<br />
  46. 46. Right after placing the order, your Criterion is very low. You expect a “Correct Rejection,” where you don’t hear anything and nothing is at the door. This criterion increases risks of “Misses,” though. If they miraculously try to deliver a pizza 5 minutes after you call, you might not hear them ringing your doorbell!<br />
  47. 47. However, 40 minutes later, your Criterion changes to high sensitivity. You want pizza! You want a “Hit,” but that also risks “False Alarms,” or thinking you hear a doorbell when there really was none.<br />
  48. 48. What you expect, what you are doing, and how much you care about detecting the stimulus matters!<br />Perception is subjective.<br />
  49. 49. Main Point 2. <br />Perception is SUBJECTIVE, not absolute.<br />Different people can select, organize, and interpret the same stimulus differently.<br />The same person can select, organize, or interpret the same stimulus differently on different occasions.<br />
  50. 50. These ideas can be implemented and controlled in cockpit design, pilot training, and FAA regulations.<br />Human Factors Engineering is an Applied field where Psychologists and other professionals use these ideas.<br />Other situations do not have such extreme oversight, but lives are still at stake…<br />
  51. 51. Example in Nursing<br />Alarm Fatigue<br />Nurses constantly hear alarms going off during their jobs. Low battery alerts, I/V alerts, monitor alerts… The beeps, buzzes, and alarms each day can number in the 100s.<br />The problem is that some of these are trivial and others are life threatening.<br />
  52. 52. Example in Nursing<br />Situation: a nurse needs to hear a life threatening alarm<br />Signal Detection Theory<br />The loudness, pitch, and timbre of the alarm matters<br />The “noise” in this case is all of the other beeps, blips, buzzes, and low priority alarms going off<br />The decision criterion is the nurse’s attentiveness and focus on the alarms<br />
  53. 53. Example in Nursing<br />Situation: a nurse needs to hear a life threatening alarm<br />Possible Outcomes<br />Hit– Nurse hears alarm, emergency response started<br />Correct Rejection – Nurse hears no alarm, nothing is wrong<br />False Alarm – Nurse “hears” alarm, emergency response started unnecessarily: wastes resources, time, and money. Is embarrassing…<br />Miss– Nurse hears no alarm, a person suffers, or worse…<br />
  54. 54. Example in Nursing<br />The problem is that the diverse cacophony of alarms can lead to a criterion that looks like this:<br />
  55. 55. Example in Nursing<br />Getting used to not reacting to alarms (Correct Rejections) leads to an increase risk of Misses.<br />
  56. 56. Example in Nursing<br />Unfortunately, there are many manufacturers of equipment. Each hospital may have various models of equipment, all with different alarms. Different departments in the same hospitals have different systems…<br />There is no equivalent to the airline manufacturer who designs everything in a cockpit to work together, with FAA oversight.<br />Finding a solution needs applied research. Psychology is essential.<br />
  57. 57. Summary<br />In this slideshow, we used several topics from your text to introduce sensation and perception.<br />Psychologists who study sensation and perception can be basic researchers or applied researchers.<br />Sometimes basic research (spending years studying how people notice differences between sounds) can become essential for applied research.<br />
  58. 58. Summary<br />You read examples of Thresholds and Just Noticeable Differences<br />From this, we illustrated the first main point:<br />There is variability in sensation.<br />For different stimuli, sensation is relative.<br />Then you read a descriptions of examples of using Signal Detection Theory<br />From this, we illustrated the second main point:<br />Perception is subjective, not absolute<br />

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